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Ophthalmic Survey in the Solomon Islands
O P H T H A L M I C S U R V E Y IN T H E S O L O M O N I S L A N D S DAVID L. VERLEE, M . D .
Bethesda, Maryland Many of the afflictions that beset modern man have been ascribed either wholly or in part to factors in his culture. Such entities as hypertension and dental caries have been found uncommon in certain non-Western societies, and are thought to be related in some manner to modern twentieth century culture. " The descriptive study of population groups having little or no exposure to Western culture provides a basis for comparison with our society. By following such a study with longitudinal observations, disease processes may be related to the nature, extent, and duration of Western acculturation. For example, if one can document the low frequency of a specific disease process in a nonWesternized population, one would expect that if this disease were in fact associated with Western civilization and culture, it would be acquired by this population as its Westernization increased. In a broader sense, such studies provide a basis for speculating on the general relationship of culture to the entire spectrum of the biologic status of man, including such factors as physique, growth, maturation and other normal biologic characteristics.
will be followed in the years to come by additional investigations. This paper presents one aspect of this study: the results of the ophthalmologic evaluation of these two groups.
During July and August, 1966, a biomedical team directed by members of the Department of Anthropology at Harvard University studied two such non-Western groups in the Solomon Islands. This pilot study was a first step in a proposed long-range investigation of culture, biology and disease among native groups in the Solomon Islands, and
Bougainville, though one of the chain of islands in the Solomon group, is actually a part of the Trust Territory of Papua and New Guinea and is administered by Australia. The remaining Solomon Islands, a British protectorate, are administered by Great Britain. The approximately 6,000 Nasioi on Bougainville live in small hamlets near the coastal town of Kieta, at the southeast end of the island. The population of the study area consisted of 271 Nasioi natives living in three hamlets approximately 17 miles inland from Kieta. All members of the three hamlets were studied except for 25 persons
1
STUDY GROUPS
3
From the Section on Ophthalmic Field and Developmental Research, Epidemiology Branch, National Institute of Neurological Diseases and Blindness, Bethesda, Maryland. This work was undertaken in collaboration with a research project by the Peabody Museum and Department of Anthropology, Harvard University, supported by U S P H S Grant GM-13482 of the National Institute of General Medical Sciences.
The first of the two groups of subjects studied were natives of the Nasioi tribe on the Island of Bougainville; the second was comprised of members of the Kwaio tribe on the Island of Malaita (see map, fig. 1 ) . The people of the particular geographic areas which were studied were selected because, prior to the biomedical evaluation, they had been studied for approximately 18 months by a social anthropologist who had conducted an ethnographic study, had learned the language, and had become intimately acquainted with the people. The anthropologist's labor in laying the ground work, establishing rapport and enlisting the participation of the natives was, of course, invaluable for the survey. The biomedical team, consisting of physicians and anthropologists, spent approximately one month studying each population group, performing examinations systematically on a production line basis.
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OPHTHALMIC SURVEY IN SOLOMON ISLANDS
Fig. 1 ( VerLee). Map showing location of Bougainville and Malaita.
(table 1) who, because of absence at the time of the study or because of unwillingness to participate, could not be included. The Kwaio, numbering about 6,280, live near Sinelagu Harbor on the east coast of the island of Malaita, near the southeast end of the Solomon chain. The Kwaio live in small settlements usually consisting only of members of a family group. Here the population of the study area consisted of 522 Kwaio natives living in 62 settlements in the interior of the island. At the time of the study, there appeared to be an epidemic of respiratory tract infections which prevented participation by some members, and this, in addition to a few persons with marked senility as well as 30 persons who were away from home, accounted, .for the 113 members in the denned populatiqn. group who were not examined (table 1 ) . An additional 34 subjects, who were related genealogically but not geographically to the study population, also were examined. The age and sex distri-
bution of both study populations and the subjects participating in the study are shown in Table 1-A. METHOD
Examinations of both population groups were carried out in native-constructed dwellTABLE 1 S T U D Y POPULATION
Bougainville (Nasioi Tribe) Number of villages or settlements studied Total census of villages or settlements studied Number of examinees from villages or settlements studied Percent participation Additional examinees from other settlements genealogically related to study group Total persons examined
Malaita (Kwaio Tribe)
3
62
271
522
246 90.7
409 78.4
11
34
257
443
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AMERICAN JOURNAL OF OPHTHALMOLOGY
A U G U S T . 1968
T A B L E 1-A STUDY POPULATION—AGE A N D S E X DISTRIBUTION
Bougainville (Nasioi Tribe)
Age (yr)
No. in Study Group Male
Malaita
l i t imroirt I n r \ o 1 ^jvwdiu x riuc/
No. Examined
Female
Total
Male
No. in Study Group
Female Total
Male
Female Total
ixt*. ijXüiiiineu
Male Female Total
0- 9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89
57 16 16 26 17 7 4 0 0
37 24 16 19 20 8 4 0 0
94 40 32 45 37 15 8 0 0
54 16 16 22 12 5 2 0 0
34 24 16 19 14 8 4 0 0
88 40 32 41 26 13 6 0 0
65 53 48 36 29 36 13 4 3
53 64 46 32 32 26 15 1 0
118 117 94 68 61 62 28 5 3
59 41 33 27 21 31 10 2 0
46 57 39 25 29 17 6 0 0
105 98 72 52 50 48 16 2 0
Total
143
128
271
127
119
246
287
269
556
224
219
443
ings, larger but otherwise similar to those in which the natives themselves live (fig. 2 ) . Under the supervision of the anthropologist, these dwellings had been constructed specifically for the biomedical investigations and included an area dark enough for an adequate ophthalmic examination. The medical evaluation of the examinees included a general physical examination, ophthalmic evaluation, electrocardiogram, dental evaluation (including plaster casts of both jaws), hematologic evaluation, blood chemistry, and urinalysis. Anthropologic investigations included
photographs, anthropometry, spectrophotometric determinations of skin color, somato-typing, taste-testing and examination of skin biopsies of selected examinees for melanin content and distribution. The ophthalmic examination consisted of the following procedures : 1. Visual acuity determination. The visual acuity was tested at a 6-meter distance, using the Snellen linear illiterate E chart (fig. 3 ) . The native interpreter proved invaluable, in this as well as in other phases of the examination, in helping the subjects to understand and perform the tests.
Fig. 2 (VerLee). Examination facilities on Bougainville. The walled-off area at the extreme right provided a darkened area for the ophthalmic examinations.
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307
Fig. 3 (VerLee). Testing the visual acuity of a Nasioi mother. A native boy who had attended mission school and had learned some English helped perform the tests.
2. External ocular examination. A general examination of the external eye and adnexa was performed, including evaluation of the conjunctiva, cornea, lids and lacrimal apparatus. Corneal arcus, common in these people, was subjectively graded in all examinees on a scale from 0 to 4. A grade of 0 was assigned when no trace of arcus could be seen with the naked eye on close scrutiny. A grade of 1 was given when the arcus was barely visible, whereas a grade of 4 indicated a wide, dense corneal band. An arcus whose size and density was intermediate between that of Grades 1 and 4, was assigned a grade of 2 or 3. Eversion of the upper lid was performed on all examinees, and the upper palpebral conjunctiva carefully examined. The loupe was used for further detailed examination only if pathologic findings were encountered upon inspection with the naked eye. The pupillary reaction to light, both consensual
and direct, as well as reaction to accommodation was noted. 3. Motility examination. Prior to atiministration of the cycloplegtc drug, examination of ocular motility was performed. This evaluation included ocular version movements, a prism and alternate cover test for heterophoria and heterotropia (with fixation maintained at a 6-meter distance), and near point of convergence (fig. 4 ) . 4. Refraction. Following the motility examination, the pupils of all subjects were dilated with 1% cyclopentolate hydrochloride using two drops in each eye. ( T o reduce the residual accommodation as much as possible, the use of 1% atropine sulfate eye drops had been considered, but because of uncertainties as to how the natives might react to prolonged paralysis of accommodation, cyclopentolate hydrochloride was substituted.) Because of the nature of the examination procedure, with the examinees visiting var-
AMERICAN JOURNAL OF O P H T H A L M O L O G Y
A U G U S T , 1968
Fig. 4 (VerLee). Testing the near point of convergence on a young Nasioi boy. A number on the left arm identified each subject for the study.
ious examiners at different times, the interval from dilation to retinoscopy could not be held constant, and therefore varied from 30 to 60 minutes. Using a battery-powered retinoscope, retinoscopy was performed with the subject fixing at six meters. In those subjects in which the visual acuity was 20/30 or poorer, a manifest (subjective) refraction was performed in addition to retinoscopy, to determine the best possible corrected visual acuity. 5. Fundus examination. Ophthalmoscopy was performed through a dilated pupil using a battery-powered direct ophthalmoscope. 6.. Tonometry. With the subject lying on a cot, one drop of 1% proparacaine hydrochloride was instilled into each eye. Intraocular pressure was determined with a Schip'tz tonometer using a 5.5 gm weight. T o maintain sterility as well as obviate the need for cleaning the tonometer, a sterile latex rubber tonometer footplate cover was used for each examinee. 7. Photography. All abnormal ocular findings were photographed using a 35 mm camera with close-up lenses, and a battery-powered electronic Hash unit. Abnormal fundi were photographed with a hand-held portable fundus camera fitted with a specially constructed wet cell battery power unit.
RESULTS AND COMMENTS
Due to lack of cooperation (usually because of young age) not all tests could be performed on all subjects and therefore the number of participants for the various examinations differs. 1. Visual acuity. The superb uncorrected visual acuity in 512 subjects is shown in Table 2. O f these 1,024 eyes, 93.2% demonstrated a visual acuity of 20/20 or better, and 95.3% of all 512 subjects had a visual acuity of at least 20/20 in the better eye. In only 24 eyes was the visual acuity 20/40 or poorer ; these 24 eyes, all of which occurred in fully grown subjects (over 15 years old) are shown in Table 3. The vision in eight of these eyes could be improved to 20/30 or better with correction of a refractive error, and an additional 13 showed pathologic conditions which could account for the decreased visual acuity. There were only three eyes (all with visual acuity of 20/50) in which the acuity could not be improved with refraction or in which no pathologic condition could be demonstrated which might account for the decreased acuity. If the 13 eyes with pathologic changes are excluded, 94.5% of all eyes, and 96.3% of the better eyes in each subject, had uncorrected visual acuity of 20/20 or better.
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309
2
V I S U A L ACUITY I N 5 1 2 SUBJECTS
All 1024 Eyes Visual Acuity 20/15 20/20 20/30 20/40 20/50 20/100 20/200 20/400 Finger counting Light perception N o light perception Total
Better Eye Only (512 Eyes) by Age Groups (yr)
%
No.
No.
0-14
15+
. Total No.
%
No.
%
263 72 16 2 3 0 0 1 0 1
73.4 20.1 4.5 0.6 0.8 0.0 0.0 0.3 0.0 0.3
396 92 17 2 3 0 0 1 0 1
77.3 18.0 3.3 0.4 0.6 0.0 0.0 0.2 0.0 0.2
%
769 186 45 4 11 1 2 2 0 2
75.1 18.1 4.4 0.4 1.1 0.1 0.2 0.2 0.0 0.2
133 20 1 0 0 0 0 0 0 0
86.4 13.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2
0.2
0
0.0
0
0.0
0
0.0
1024
100.0
154
100.0
358
100.0
512
100.0
Excellent visual acuity has been reported in other societies which are unacculturated by Western standards. In his studies of Xavante Indians of Brazil, Neel found a binocular visual acuity of 20/15 or better in 12 of the 13 males on whom determinations were performed. He stated that, probably for cultural reasons, the females did not seem to be able to understand and perform the visual acuity test as well as the males. Neel also cites Mattos' study* of Xingu and 1
Xavante Brazilian Indians which showed binocular visual acuity of 20/15 or better in 55 of 77 (71.4%) males. Mann, " in her study of 145 Australian aborigines, found 126 (86.9%) with a binocular visual acuity of 6/6 or better, even though many had trachoma of varying degrees. Several had phenomenal visual acuity, two described as having 17/5. Studies performed on Western population groups, on the other hand, suggest a s
a
TABLE 3 DESCRIPTION OF THE 24 EYES WITH VISUAL ACUITY OF 2 0 / 4 0 OR POORER
Number of Eyes Not Correctable to 20/30 or Better Visual Acuity
Correctable to 20/30 or Better*
Senile Cataract
Corneal Opacities
Macular Changes
Traumatic Cataract
Phthisis Bulbi
No Explanation Found for Decreased Acuity
Total No. of Eyes
20/40 20/50 20/100 20/200 20/400 Light perception N o light percpetion
1 6 1 0 0 0
0 2 0 2 2 0
2 0 0 0 0 0
1 0 0 0 0 0
0 0 0 0 0 2
0 0 0 0 0 0
0 3 0 0 0 0
4 11 1 2 2 2
0
0
0
0
0
2
0
2
Total
8
6
2
1
2
2
3
24
1
With manifest refraction.
310
A U G U S T , 1968
AMERICAN JOURNAL OF OPHTHALMOLOGY TABLE 4 DISTRIBUTION OF REFRACTIVE ERRORS IN 1155
EYES
Cylindrical Error (Diopters) Number of Eyes +0.25 +0.50
•a a
PI
o •a
+ 2 50 + 2 25 + 2 00 + 1 75 + 1.50 +1.25 +1.00 +0.75 +0.50 +0.25 +0.00 -0.25 -0.50 -0.75 -1.00 -1.25 -1.50
+0.75 +1.00 +1.25 +1.50 +1.75 +2.00 +2.25
+2.50
1 6 1 25 17 71 58 251 159 67 1 2
2 1 21 17 42 54 27 3 2
5 3 22 12 86 109 23 4 2
1 2 1 12 3 8
1094 "spherical" eyes (94.7%)
61 "nonspherical" eyes (5.3%)
much smaller proportion of the general population with such excellent uncorrected visual acuity. In Sorsby's study of 1,033 British recruits, only 67.7% had visual acuity of 6/6 in the better of the two eyes. Karpinos obtained data on the visual acuity of 273,000 recruits, and found that 82% of the Negroes 6
7
and 69% of the Caucasians had uncorrected binocular visual acuity of 20/20 or better. 2. Refractive errors. The distribution of the refractive errors in 1,155 eyes (representing 581 individuals) in which retinoscopy could be performed is shown in Table 4. The eyes are divided into two groups,
TABLE 5 DISTRIBUTION OF REFRACTIVE ERRORS IN 1,155
Refractive Error (Diopters) +2.50 +2.25 +2.00 +1.75 +1.50 +1.25 +1.00 +0.75 +0.50 +0.25 +0.00 -0.25 -0.50
"Spherical" Eyes* ( < 0 . 5 D Cylinder) No.
%
EVES
"Non-Spherical" Eyesf ( > 0 . 5 D Cylinder) No.
%
Total No.
1 0 6 8 29 60 100 186 414 209 74 5 2
0.1 0.0 0.5 0.7 2.7 5.5 9.1 17.0 37.8 19.1 6.8 0.5 0.2
0 0 0 0 2 2 6 2 24 6 16 1 2
0.0 0.0 0.0 0.0 3.3 3.3 9.8 3.3 39.3 9.8 26.3 1.6 3.3
1 0 6 8 31 62 106 188 438 215 90 6 4
1094
100.0
61
100.0
1155
* Spherical equivalent (sphere+0.50 cylinder), t Less ametropic meridian.
% 0.1 0.0 0.0 0.7 2.7 5.4 9.2 16.3 37.9 18.6 7.8 0.5 0.3 100.0
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spherical and nonspherical, following the convention used in other studies - which consider eyes with a cylinder of 0.5 diopter or less to be spherical and those with greater than 0.5 diopter, nonspherical or astigmatic. The distribution of refractive errors is summarized in Table 5 and Figure 5, in which the spherical equivalent (sphere +0.50 cylinder) is used for the spherical eyes, and the less ametropic meridian for the nonspherical eyes. In general, this analysis follows the format used by Sorsby* in his recent study of British subjects. Two significant observations can be made from these data. First, only a very small number of eyes (10 of the 1,155 eyes, or 0.8%) were myopic, none by more than 0.5 diopter ; and second, relatively few eyes had substantial amounts of astigmatism, only 61 eyes (5.3%) having 0.75 of a diopter or more. A s can be seen, the great majority of the eyes fall in the lower degrees of hyperopia, with over 98% of all eyes having from 0 to 2 diopters of hyperopia. This undoubtedly does not reflect the true distribution of the hyperopic eyes, since cycloplegia was not complete. Incomplete cycloplegia, however, should have no effect on the distribution of the myopic eyes. 9
The
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OPHTHALMIC SURVEY IN SOLOMON ISLANDS
9
astigmatism of 0.75 diopter or more
found in 61 eyes was mostly of low degree, with only 13 (21.3%) having greater than 1 diopter. Figure 5 illustrates that the astigmatic eyes were fairly evenly distributed over the range of spherical errors. The rarity or absence of myopia and astigmatism has been shown in two excellent studies of non-Western societies, those of Holm and Skeller. Holm, in his study of African Negroes, reported myopia in only 14 (0.3%) of 4,926 nonselected eyes. Two of these 14 eyes had myopia of 0.5 diopter, with the other five ranging from 3 to 9 diopters. Of these 4,926 eyes, only 42 (0.9%) had astigmatism of greater than 1 diopter. Skeller's study of refractive errors in 1,450 eyes of all Angmassalik Eskimos in Greenland showed only 1% to be myopic, all of which were less than 1.5 diopters. However, 292 of the 1,450 eyes (20.1%) had astigmatism of greater than 0.5 diopter; 183 ( 12.6% ) had greater than 1 diopter. It also has been reported that the frequency of myopia is low or nonexistent in American Indians, "* Australian aborigines, " and the Polynesians of Samoa. The low frequency of myopia in these population groups is in contrast to the higher frequencies reported in studies of Western populations. Two such studies, dealing with 8
9
5
5
0
10
40 T o t a l height * all eyes EZ%3 "Non-spherical" eyes 30 Fig. 5 (VerLee). Distribution of refractive errors in 1,155 eyes. Plotted by spherical equivalent (sphere + 0.50 cylinder) for eyes with 0.5 diopter or less cylinder ("spherical" eyes), and by the less ametropic meridian for eyes with greater than 0.5 diopter cylinder ("nonspherical" eyes).
I
I "Spherical" eyas
¡3
>U
20
u e in O.
10
-
T~—I—"
I
"—I— —I—'—I— —I 1
1
•
I
•
I
I
O.90 0.25 -04- 025 OSO 0.7S 1.00 I.2S 1.50 1.75 2.O0 225 2 5 0 R E F R A C T I V E E R R O R (diopters)
312
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A U G U S T , 1968
TABLE 6 HETEROTROPIA—•DISTRIBUTION OF 13 CASES FOUND IN 616 SUBJECTS No. of Cases
Measurement*
Age Range (vr)
Mean Age (vr)
Comitant deviations Intermittent exotropia Intermittent exotropia Constant exotropia Intermittent esotropia
S 5 1 1
D>N N>D D=N N>D
22^7 27-63 50 13
33.4 45.2 50.0 13.0
Noncomitant deviation Paresis of third cranial nerve
1
51
51.0
Type of Deviation
* D > N indicates that the deviation while fixing at distance (6 meters) is greater by 10 prism diopters or more than while fixing at near (1/3 meter). Conversely, N > D indicates the near deviation is greater by 10 prism diopters or more than the distance deviation. D = N indicates that there is less than 10 prism diopters difference between the distance and near deviations.
relatively unselected material, include those of Sorsby and Stromber. In Sorsby's study of 2,066 eyes of British recruits, 11.0% were myopic; the myopia was greater than 1.0 diopter in 6.6% of all eyes. Astigmatism of greater than 0.5 diopter was present in 18.7%. In Stromberg's study of 5,122 eyes of Swedish conscripts, myopia was present in 8.86% and was greater than 1 diopter in 3.4%. Schepens and Marden have recently summarized data on the frequency of myopia. Most of their studies deal with eye patients and therefore represent selected material, but the studies indicate an overall incidence of myopia from 5% to 18% in European and American populations. These authors also cite studies of Chinese and Japanese which suggest an even higher frequency of myopia in these groups. 3. Ocular motility. A. Heterotropia Binocular eye movements (versions) were normal in all 616 subjects except one in whom a noncomitant (paretic) deviation was encountered. This was a 51-year-old woman who stated she had had drooping of the left eyelid for many years. On examination, the left palpebral fissure was 3 mm less than the right, with the left eye displaced interiorly and temporally. There was limitation of elevation and adduction, but the pupillary reactions to light and accomodation were intact. 8
11
12
A probable diagnosis of left third cranial nerve paresis was made. Cover testing on the 616 subjects revealed 12 cases (1.9%) of comitant heterotropia (table 6 ) , of which only one was constant—a case of exotropia measuring approximately 15 prism diopters for both distance and near in a 50-year-old man. Of the 10 intermittent exotropia cases, five had at least 10 prism diopters greater deviation for distance than for near (divergence-excess type) and occurred in a relatively young age group (mean age 33.4 years). The other five cases of intermittent exotropia, all of which had at least 10 prism diopters greater deviation for near than for distance (convergence-insufficiency type), occurred in a relatively older age group (mean age 45.2 years). Esotropia was considerably less common than exotropia, with only one case (0.2%) found in the 616 subjects. This case, in a 13-year-old girl, demonstrated two prism diopters of esophoria at distance, and a variable amount of esotropia (8-15 prism diopters) at near. Mann * stated that esotropia has been reported absent or rare in the Melanesians of New Guinea, Fiji, and New Britain; it has also been found rare in the people of Southeast Asia, in Indians of North and South America, Australian aborigines, and some tribes in Africa. She also stated that, unlike esotropia, exotropia seems universally dis5
d
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and may not be representative of the general population. Further, comparison of such results are difficult because of the different methods used for measuring heterophoria. studying Thus, Grieve and Archibald, 1,209 healthy adult (age I7yi to 30 years) males with no high refractive errors, used the Maddox wing, and found 184 (15.2%) with greater than six prism diopters of exophoria. Eight of the 1,209 (0.7%) had more than six prism diopters of esophoria. Young in studying 905 refraction patients, found that 18.5% had greater than eight prism diopters of exophoria as measured with the Maddox rod. It should be noted that in both studies, unlike the present one, measurements were performed at near. Nevertheless, this data would suggest a wider spread of heterophoria values in Western groups than in the present study.
tributed throughout the world, although the frequency is also low. Available statistics in Western societies, usually from studies performed in schoolage children, suggest a frequency of comitant strabismus from 1% to 2%. In the present study, if the 262 children aged 14 years or under are considered separately, the only case found in this age group places the frequency at 0.4%. This would suggest, at least in children, that strabismus is less common in Melanesian societies than in Westernized cultures.
14
13
15
B. Heterophoria The results of alternate cover testing of the remaining 604 subjects are shown in Table 7. The majority (93.6%) of subjects had orthophoria or an exophoria ranging from 1 to 8 prism diopters. Only 3% had more than 8 prism diopters of exophoria and only 3.4% had esophoria, less than 6 prism diopters in all cases. The breakdown by age indicates there was a general increase in exophoria with increasing age. Accurate statistics on the distribution of heterophoria in Western societies are difficult to obtain because the few such studies performed have used selected case material,
C. Near-point of convergence The distribution of the near-point of convergence ( N P C ) determinations for the 573 subjects participating in this test is shown in Table 8. As might be expected, there is a tendency toward less convergence ability in the older age groups. Just under 50% of subjects 30 years of age or older had an
TABLE 7 D I S T R I B U T I O N O F H E T E R O P H O R I A I N 604
SUBJECTS*
Age (yr) Heterophoria (Prism d,opters)
4
N
q
%
N
o
%
N
q
5
+
T
%
N
q
°'
a l
%
5-6 3-4 1-2 0
0 5 2 160
0.0 2.1 0.8 65.8
1 8 2 73
0.4 3.1 0.8 27.9
0 2 0 18
0.0 2.0 0.0 18.2
1 15 4 251
0.0 2.5 0.7 41.6
1-2 3-4 5-6 7-8 9-10 11-12 13-14 15
18 31 21 6 0 0 0 0
7.4 12.8 8.6 2.5 0.0 0.0 0.0 0.0
28 64 65 12 5 1 2 1
10.7 24.3 24.7 4.6 1.9 0.4 0.8 0.4
6 22 27 15 6 2 1 0
6.1 22.2 27.2 15.2 6.1 2.0 1.0 0.0
52 117 113 33 11 3 3 1
8.6 19.4 18.7 5.5 1.8 0.5 0.5 0.2
243
100.0
262
100.0
99
100.0
604
100.0
Total
* Measured by alternate cover testing with fixation at 6 meters.
A U G U S T , 1968
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314
TABLE 8 NEAR POINT OF CONVERGENCE (NPC) IN 573 SUBJECTS Age (yr) NPC (mm.)
30-49
0-29 No.
50+
Total
%
No.
%
No.
%
No.
%
77 0 0 6 48 20
51.0 0.0 0.0 4.0 31.8 13.2
33 0 0 5 23 9
47 .1 0 .0 0 .0 7 .1 32 .9 12 .9
351 1 0 31 152 38
61.3 0.2 0.0 5.4 26.5 6.6
151
100.0
70
573
100.0
0 5-24 25-49 50-99 100-199 200 +
241 1 0 20 81 9
68.5 0.3 0.0 5.7 23.0 2.5
Total
352
100.0
NPC of 100 mm or more ; this was found in only 25.5% of those under the age of 30 years. 4. Tonometry. The distribution of intraocular pressure determinations as measured with the Schip'tz tonometer for 812 of the 814 eyes in which Schip'tz determinations could be performed is shown in Figure 6. Not included in this distribution are two eyes (one from each of two subjects) with traumatic injuries and elevated intraocular pressure thought to be secondary to the injury. The intraocular pressure in the fellow eye in each of these two cases was within normal limits. Plotted on the graph (fig. 6 ) is the percent of eyes for each of the scale readings on the Schätz tonometer. Also shown is the equivalent pressure in mm Hg (1955 revision of the Schip'tz conversion table) and the number of eyes for each of the scale readings.
100 .0
The mean intraocular pressure in the 812 eyes was 15.97 mm Hg with a standard deviation of ±2.24. Only three eyes (0.4%) were encountered with intraocular pressures greater than 21 mm Hg, the figure sometimes used in Western populations to represent the upper limit of normal for the majority of the population. The intraocular pressure in each of these three eyes was 22.4 mm Hg, only slightly higher than this upper limit. 18
Many studies of the distribution of intraocular pressure in Western populations have been undertaken, five of which are summarized in Table 9, together with data from the present study. It is evident that the mean intraocular pressure for all these studies does not vary greatly, but the standard deviation of the present study is smaller than those of Western populations, indicating a smaller spread of values. 17-20
Fig. 6 (VerLee). Distribution of Schätz intraocular pressure determinations in 812 eyes.
SCHIOTZ SCALE READING
7.S 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5
EQUIVALENT PRESSURE (mm-Ho.) 11.2
12.2 13.4 14.6 15.9 17.3 18.9 20.6
22.4
NUMBER OF EYES
84
3
8
77
123 182 209 79
45
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TABLE COMPARISON OF TONOMETRIC DATA WITH
Author
Location
Age Range (yrs.)
315
ISLANDS
9
THAT OF W E S T E R N POPULATION
T y p e of Study
No. of Subjects
No. of Eyes
Method
GROUPS Intraocular Pressure (mm Hg)
Mean
S. D .
Distribution Curve
Leydbecker and assoc. (19S8) Graham and Hollows (1964)
Bonn, Germany South Wales Wales
6-70
self-selection
10,000
19,880
Schifitz
15.50
2.57
skew
40-74
total community
4,246
8,492
Schitftz
15.1
2.90
skew
Armaly. M . L. (1965) Schwartz and assoc. (1966) Bankes. J * and assoc. VerLee. D . L. (present study)
Des Moines, Iowa Nesquehoning. Pa. Bedford, England Solomon Islands
20-89
sample
2,327
4,652
Applanation Applanation
15.9 16.85
2.86 3.75
skew skew
25-70 +
total community selfselection total community
1,004
Schätz
15.24
3.34
skew
5,941
11,849
Schi0tz
16.29
3.43
skew
Schitftz
15.97
2.24
no skew
40
+
3-79
502
407
812
* Bankes. J., Perkins, E. S.. Tsolabis, S. and Wright. J. E.: The Bedford Glaucoma survey. (Unpublished data.)
The distribution of intraocular pressure in the studies of Western population groups listed in Table 9, as well as in other studies, show a skew toward higher pressure readings which has been interpreted by some to indicate the presence of a separate "glaucoma population." The absence of such a skew in the present study is shown most clearly when the distribution of intraocular pressures is plotted on a cumulative frequency graph (fig. 7 ) . On this graph is plotted the distribution of intraocular pressures and a straight line. The straight line is based on the mean and standard deviation of the sample, and represents a "normal" (Gaussian) distribution. On such a graph, a skew of the type occurring 17
in the studies " above, would be repre-sented by an upward curve (dotted line) of the plotted points above the normal line. As is evident from the graph, the values plotted in the present study show no such tendency. No signs of advanced glaucoma (cupping of the optic nerve head or gross visual field loss) were found. This observation, together with the absence of an upward skew in the distribution of intraocular pressures and the fact that in only three eyes was the pressure as high as 22.4 mm Hg, suggests that chronic simple glaucoma is rare or nonexistent in this population. On the basis of surveys, chronic simple glaucoma likewise has been reported rare or absent in natives in New Guinea and 17
20
316
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A U G U S T , 1968
T A B L E 10 CORNEAL ARCUS IN 618 SUBJECTS Age (yr) Arcus Grade
0-14
0 1 2 3 4 Total
15-39
%
No.
%
No.
%
No.
%
186 53 4 1 1
75.9 21.7 1.6 0.4 0.4
123 73 28 3 0
54.2 32.2 12.3 1.3 0.0
39 46 31 19 11
26.7 31.5 21.2 13.1 7.5
348 172 63 23 12
56.4 27.8 10.2 3.7 1.9
245
100.0
227
100.0
146
100.0
618
100.0
21
22
10
8
5
5
8
23
5
Total
No.
Papua, the Maoris of New Zealand, the Polynesians of Niue and Samoa, as well as natives of Tristan de Cunah in the South Atlantic, " the Cocos Kieling Islands in the Indian Ocean, "' in Australian Aboriginies, " and Indians of North and South America. " 5. Corneal arcus. The distribution of arcus, graded as previously described, is shown in Table 10. Arcus in these people is very common ; it was present in some degree in 43.6% of all 618 subjects on whom an external examination could be performed. The breakdown of subjects by age in Table 10 reveals an increased frequency of arcus in the older age groups. The majority (73.3%) of subjects aged 40 years and over had some degree of arcus, whereas this was true in only 45.8% of those aged 15 to 39 years. These findings, using the KolmogorovSmirnov test, were significantly different (p<.001). Moreover, arcus was not only more common, but also more severe in the older age groups. Of those 40 years old or more, 41.8% had an arcus graded as 2 or greater, whereas an arcus of this degree occurred in only 13.6% of those in the 15- to 39-year-old age group, and in only 2.4% of those 14 years of age or under. As concerns the pigmented races, arcus is said to be common in Indonesians of tropical areas and more common in Negroes than in whites in North America. * * In Caucasians there is a steady rise in the fre8
40 +
11
24
25
2
quency of arcus with increasing age, but there seems to be also an association of arcus with abnormalities of lipid metabolism. Hypercholesterolemia, particularly in the familial type and in younger individuals, shows such a relationship, but this is by no means consistent. A relationship between abnormalities of lipid metabolism and arcus has also been demonstrated recently in young (aged 30-45 years) Negroes, showing a positive correlation between serum cholesterol and phospholipid levels and the degree of arcus. Serum cholesterol determinations were performed in the present study and the preliminary evaluations of the association of the degree of arcus with the serum cholesterol level did not appear to indicate a significant relationship. This relationship will be evaluated more fully in a future publication. 27
27
28
6. Pathologic conditions. The pathologic conditions observed on external and ophthalmoscopic examinations are listed in Table 11. A s can be seen, the predominant conditions found were of infectious and traumatic etiology. In a population prone to infections thought to be associated with uveitis (for example, tuberculosis and leprosy), only three cases of uveitis (all chorioretinitis) were observed. No case of anterior uveitis was encountered. The healthy appearance of the retinal vessels in older individuals was remarkable. The only case of hypertensive retinopathy encountered occurred in a man whose blood pressure was 180/120, and was
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thought to be on the basis of renal disease. Diabetic and arteriosclerotic retinopathy were nonexistent in the study subjects. In view of the widespread trachoma throughout much of the South Pacific, it is noteworthy that no trachoma was seen in the study population. Many cases of trachoma were seen, however, during the course of operating a daily clinic in both Malaita and Bougainville for natives living in the offshore islands and nearby coastal areas. The presence of trachoma in these persons but not in the study population is of interest from an epidemiologic standpoint ; no explanation was evident for this observed difference, except possibly the higher altitude and the relative social isolation of the study population from the coastal natives. It is probably of little value to attempt comparisons of the frequencies of the pathologic conditons listed in Table 1 with the frequencies reported in Western populations, since the number of involved individuals is very small, and accurate figures of the prevalence of these conditions are not available for Western populations. In addition, in Western populations, varying criteria are used for diagnosis, making valid comparisons difficult. CONCLUSIONS
It should be stressed that valid comparisons between data of the present study and samples of Western population groups are difficult because characteristics of the samples differ and different examining methods are used. Nevertheless, even taking these factors into account, the present study, as well as other studies, strongly suggests that many biologic differences exist between Western societies and those societies unacculturated by Western standards. Mam' characteristics of such peoples, of course, such as the prevalence of infectious diseases, clearly are due primarily to environmental factors. Other characteristics, particularly the relative rarity of chronic and degenerative diseases,
S O L O M O N
317
I S L A N D S TABLE
11
PATHOLOGIC CONDITIONS
ENCOUNTERED*
No. of Cases General phthisis bulbi traumatic injuries with peripheral anterior synechiae and secondary glaucoma Eyelids tinea imbricata external hordeolum sebaceous cyst fusion of temporal aspects of upper and lower lids, probably traumatic
2 2 1 1 2 1
Cornea and Conjunctiva inspissated mucus, palpebral conjunctiva conjunctivitis, purulent conjunctivitis, follicular conjunctival nevus, large cornea, opacities—traumatic and infectious Trantas spot pterygium Pinguecula, prominent
S 1 2 2
Lens cataract, traumatic cataract, senile posterior lenticonus
3 4 1
Vitreous asteroid hyalosis prominent hyaloid remnants
2 4
Choroid and Retina chorioretinitis, active chorioretinitis, healed, inactive drusen, diffuse, involving posterior pole hypertensive retinopathy
1 2 5 1
2 3 1 3
* Ametropias and heterotropias excluded.
most likely are a result of interplay of environmental and genetic factors. On the basis of family and twin studies, many biologic characteristics—for example, errors of refraction—have been found to be strongly influenced by heredity. It therefore seems reasonable to suppose that differences in the racial distribution of these characteristics are also best explained on a genetic basis, possibly through the mechanism of natural selection. For example, relaxation of selection as a result of diminished need for acute distance visual acuity by Western populations, may allow the genes contributing to myopia to be perpetuated. The role of the environment, however, must remain an open
318
AMERICAN JOURNAL OF OPHTHALMOLOGY
question. A s these population groups become more acculturated, one might expect that, unlike the many years usually necessary for genetic changes produced by natural selection to occur, biologic characteristics associated with a change in environment would manifest themselves in a relatively short period of time. For example, if myopia can result from close work, one would expect that as these people learn to read and become engaged in other tasks requiring an increasing amount of time spent with the eye in the accommodated state, the frequency of myopia in the population would increase, becoming evident in, genetically speaking, a relatively short time. Either the presence or absence of such findings would do much to increase our knowledge of the pathogenesis of many such conditions. It is hoped that insight into the relative influence of hereditary and environmental factors in the production of ocular characteristics can be gained by future investigations. SUMMARY
An ophthalmic survey of two native population groups in the Solomon Islands was performed as part of an initial complete medical and anthropologic investigation of these populations. Included in the ophthalmic examination was the evaluation of visual acuity, external disease, ocular motility, refraction, ocular fundus, and intraocular pressure. Among the observations made were the following, which are of particular interest because they differ from data on Western populations: 1. Approximately 95% of all persons had visual acuity of 20/20 or higher in the better of the two eyes. 2. Refractive errors, in particular myopia and astigmatism, were rare. Only 10 of the 1,155 (0.8%) eyes were myopic, and the myopia in all 10 was 0.5 diopter or less. A s tigmatism of 0.75 diopters or more was found in only 61 ( 5 . 3 % ) of the eyes. 3. Schätz tonometry determinations re-
A U G U S T , 1968
vealed only three of 812 eyes to have intraocular pressures over 21 mm H g ; the pressure in all three was 22.4 mm Hg. 4. Arteriosclerotic and hypertensive retinopathy were virtually absent in all age groups. ACKNOWLEDGMENTS
Grateful acknowledgment is given to Dr. J. Theodore Schwartz, Head, Section on Ophthalmic Field and Developmental Research, Epidemiology Branch, N I N D B , for his constructive suggestions both in preparation of the protocol and for evaluation of the manuscript, and to Mr. Allen R. Lewis, Office of Biometry, N I N D B , for his help in preparing and carrying out the statistical analysis of the data. REFERENCES 1. Neel, J. V., Salzano, F. M., Junqueira, P. C, Keiter, F. and Maybury-Lewis, D. : Studies on the Xavante Indians of the Brazilian Mato Grosso. Am. J. Hum. Genet 16:52,1964. 2. Niswander, J. D. : Further studies on the Xavante Indians. V I I . The oral status of the Xavantes of Simôes Lopes. Am. J. Hum. Genet 19:543, 967. 3. Lowenstein, F. W . : Blood pressure in relation to age and sex in the tropics and subtropics. Lancet 1:389, 1961. 4. Mattos, R. B. : Acuidade visual para longe a frequência de discromatopsia em indios brasileiros. Arq. Brasil. Oftal. 21:105, 1958. Cited by Neel* 5. Mann, I . : Culture, Race, Climate and Eye Disease. Springfield, III, Thomas, 1966. (a) p. 466, ( b ) p. 544, ( c ) p. 44, (d) p. 553, (e) p. 37, ( f ) p. 45, ( g ) p. 468, (h) p. 483. 6. Sorsby, A., Sheridan, M., Leary, G. A . and Benjamin, B. : Vision, visual acuity, and ocular refraction of young mea Brit Med. J. 1:1394, 1960. 7. Karpinos, B. D. : Racial differences in visual acuity. Public Health Rep. 75:1045, 1960. 8. Hohn, S.: Les états de la réfraction oculaire chez les Palénegrides au Gabon, Afrique Êquatoriale Française. Acta Ophth. Suppl. 13:1, 1937. 9. Skeller, E. : Anthropological and Ophthalmological Studies on the Angmagssalik Eskimoes. Meddelelser om Grönland, Copenhagen, C. A . Reitzels Forlag, 1954, p. 107. 10. Loschdorfer, J. : General Survey of Eye Diseases in Niue Island, American Samoa and Western Samoe. Technical information circular No. 13. South Pacific Commission, August 1955. 11. Stromberg, E. : Über refrakion and achsenlange des menschlichen auges. Acta Ophth. 14:281, 1936. 12. Schepens, C. L. and Marden, D. : Data on the natural history of retinal detachment Am. J. Ophth. 61:213,1966. 13. Duke-Elder, S.: Text-book of Ophthalmology, S t Louis, Mosby, 1949, vol. 4, p. 4004. 14. Grieve, J. and Archibald, D. H . : Some facts and figures relating to heterophoria in symptom-
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O P H T H A L M I C S U R V E Y IN S O L O M O N I S L A N D S
free individuals. Tr. Ophth. Soc. U.K. 62:285, 1942. 15. Young, C. A. : Exophoria : Analysis and treatment of 167 cases. Virginia Med. Monthly 53:25, 1926. 16. Becker, B. and Shaffer, R. N. : Diagnosis and Therapy of the Glaucomas. S t Louis, Mosby, 1965, ed. 2, p. 53. 17. Leydhecker, W . , Akiyama, K. and Neumann, H. G. : Der intraokulare Druck gesunder menschlicher Augen. Klin. Mbl. Augenh. 133:662, 1958. 18. Armaly, M. L. : On the distribution of the applanation pressure. Arch. Ophth. 73:11, 1965. 19. Schwärt, J. T. and Dell'Osso, G. G. : Comparison of Goldmann and Schi^tz tonometry in a community. Arch. Ophth. 75:788, 1966. 20. Graham, P. and Hollows, F. C. : Sources of variation in tonometry. Tr. Ophth. Soc. U.K. 84:597, 1964. 21. Mann, I. and Loschdorfer, J. : Ophthalmic survey of the territories of Papua and New Guinea 1955. Health Dept., Port Moresby, N. G., 1956, p. 47.
KELOID
319
22. Hope-Robertson, W . J. : Some ophthalmologic problems in New Zealand. Am. J. Ophth. 46:661, 1958. 23. Thygeson, P. and Dawson, C. R. : Ophthalmological problems of the American Indians. Tr. Pacific Coast Oto-Ophth. Soc. 40:49, 1959. 24. Mulock-Houwer, A. W . : Arcus senilis en pterygium. Ned. tschr. Geneesk. 78:2456, 1934. In Forsius, H . : Arcus senilis corneae : Its clinical development and relationship to serum lipids, proteins and lipoproteins. Acta Ophth. Suppl. 42:5, 1954. 25. Scott, L. C. : Arcus senilis as an accompaniment of cardiovascular disease. Southern Med. J. 24:165, 1931. 26. Kampmeier, R. H. : Arteriosclerosis and arcus senilis in the young Negro male. J. Trop. Med. Hyg. (London) 39:164, 1936. 27. Duke-Elder, S. : System of Ophthalmology. St. Louis, Mosby, 1965, vol. 8, pt. 2, p. 874. 28. Tschetter, R. T. : Arcus senilis : Its relationship to serum lipids in the Negro male. Arch. Ophth. 76:325, 1966.
OF THE
CORNEA
TIBOR G . FARKAS, M . D . AND JAMES P . ZNAJDA, M . D . Chicago, Illinois
Hypertrophic scars of the cornea are quite uncommon. Since Szokalski first described a case of corneal keloid in 1865 only 40 additional cases have been reported in the literature. In 1940, Smith collected 37 cases in his literature review. In 27 of these cases, disease, surgery or injury preceded the formation of the corneal mass. Two theories have been proposed to explain the formation of corneal keloids. Parsons, in 1904, and then Fuchs, in 1918,* suggested that they originated from the stromal cells of the iris. Fenton and Tredici, in 1964, proposed that they formed from proliferating fibrovascular tissue during the healing stage of corneal perforation. Recently we examined a corneal keloid which ap1
2
peared to support Parson's and Fuchs' suggestion that corneal hypertrophic scars originate from the iris. CASE REPORT A white female infant, first seen by us when she was three months old, had had a protruding corneal
3
5
From the Eye Research Laboratories, University of Chicago. This study was supported in part by U S P H S Grants NB-3358 and FR-55 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland.
Fig. 1 (Farkas and Znajda). Gross specimen showing iris prolapsing through the corneal perforation. ( x 5 . )
Bethesda, Maryland Many of the afflictions that beset modern man have been ascribed either wholly or in part to factors in his culture. Such entities as hypertension and dental caries have been found uncommon in certain non-Western societies, and are thought to be related in some manner to modern twentieth century culture. " The descriptive study of population groups having little or no exposure to Western culture provides a basis for comparison with our society. By following such a study with longitudinal observations, disease processes may be related to the nature, extent, and duration of Western acculturation. For example, if one can document the low frequency of a specific disease process in a nonWesternized population, one would expect that if this disease were in fact associated with Western civilization and culture, it would be acquired by this population as its Westernization increased. In a broader sense, such studies provide a basis for speculating on the general relationship of culture to the entire spectrum of the biologic status of man, including such factors as physique, growth, maturation and other normal biologic characteristics.
will be followed in the years to come by additional investigations. This paper presents one aspect of this study: the results of the ophthalmologic evaluation of these two groups.
During July and August, 1966, a biomedical team directed by members of the Department of Anthropology at Harvard University studied two such non-Western groups in the Solomon Islands. This pilot study was a first step in a proposed long-range investigation of culture, biology and disease among native groups in the Solomon Islands, and
Bougainville, though one of the chain of islands in the Solomon group, is actually a part of the Trust Territory of Papua and New Guinea and is administered by Australia. The remaining Solomon Islands, a British protectorate, are administered by Great Britain. The approximately 6,000 Nasioi on Bougainville live in small hamlets near the coastal town of Kieta, at the southeast end of the island. The population of the study area consisted of 271 Nasioi natives living in three hamlets approximately 17 miles inland from Kieta. All members of the three hamlets were studied except for 25 persons
1
STUDY GROUPS
3
From the Section on Ophthalmic Field and Developmental Research, Epidemiology Branch, National Institute of Neurological Diseases and Blindness, Bethesda, Maryland. This work was undertaken in collaboration with a research project by the Peabody Museum and Department of Anthropology, Harvard University, supported by U S P H S Grant GM-13482 of the National Institute of General Medical Sciences.
The first of the two groups of subjects studied were natives of the Nasioi tribe on the Island of Bougainville; the second was comprised of members of the Kwaio tribe on the Island of Malaita (see map, fig. 1 ) . The people of the particular geographic areas which were studied were selected because, prior to the biomedical evaluation, they had been studied for approximately 18 months by a social anthropologist who had conducted an ethnographic study, had learned the language, and had become intimately acquainted with the people. The anthropologist's labor in laying the ground work, establishing rapport and enlisting the participation of the natives was, of course, invaluable for the survey. The biomedical team, consisting of physicians and anthropologists, spent approximately one month studying each population group, performing examinations systematically on a production line basis.
304
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305
OPHTHALMIC SURVEY IN SOLOMON ISLANDS
Fig. 1 ( VerLee). Map showing location of Bougainville and Malaita.
(table 1) who, because of absence at the time of the study or because of unwillingness to participate, could not be included. The Kwaio, numbering about 6,280, live near Sinelagu Harbor on the east coast of the island of Malaita, near the southeast end of the Solomon chain. The Kwaio live in small settlements usually consisting only of members of a family group. Here the population of the study area consisted of 522 Kwaio natives living in 62 settlements in the interior of the island. At the time of the study, there appeared to be an epidemic of respiratory tract infections which prevented participation by some members, and this, in addition to a few persons with marked senility as well as 30 persons who were away from home, accounted, .for the 113 members in the denned populatiqn. group who were not examined (table 1 ) . An additional 34 subjects, who were related genealogically but not geographically to the study population, also were examined. The age and sex distri-
bution of both study populations and the subjects participating in the study are shown in Table 1-A. METHOD
Examinations of both population groups were carried out in native-constructed dwellTABLE 1 S T U D Y POPULATION
Bougainville (Nasioi Tribe) Number of villages or settlements studied Total census of villages or settlements studied Number of examinees from villages or settlements studied Percent participation Additional examinees from other settlements genealogically related to study group Total persons examined
Malaita (Kwaio Tribe)
3
62
271
522
246 90.7
409 78.4
11
34
257
443
306
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A U G U S T . 1968
T A B L E 1-A STUDY POPULATION—AGE A N D S E X DISTRIBUTION
Bougainville (Nasioi Tribe)
Age (yr)
No. in Study Group Male
Malaita
l i t imroirt I n r \ o 1 ^jvwdiu x riuc/
No. Examined
Female
Total
Male
No. in Study Group
Female Total
Male
Female Total
ixt*. ijXüiiiineu
Male Female Total
0- 9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89
57 16 16 26 17 7 4 0 0
37 24 16 19 20 8 4 0 0
94 40 32 45 37 15 8 0 0
54 16 16 22 12 5 2 0 0
34 24 16 19 14 8 4 0 0
88 40 32 41 26 13 6 0 0
65 53 48 36 29 36 13 4 3
53 64 46 32 32 26 15 1 0
118 117 94 68 61 62 28 5 3
59 41 33 27 21 31 10 2 0
46 57 39 25 29 17 6 0 0
105 98 72 52 50 48 16 2 0
Total
143
128
271
127
119
246
287
269
556
224
219
443
ings, larger but otherwise similar to those in which the natives themselves live (fig. 2 ) . Under the supervision of the anthropologist, these dwellings had been constructed specifically for the biomedical investigations and included an area dark enough for an adequate ophthalmic examination. The medical evaluation of the examinees included a general physical examination, ophthalmic evaluation, electrocardiogram, dental evaluation (including plaster casts of both jaws), hematologic evaluation, blood chemistry, and urinalysis. Anthropologic investigations included
photographs, anthropometry, spectrophotometric determinations of skin color, somato-typing, taste-testing and examination of skin biopsies of selected examinees for melanin content and distribution. The ophthalmic examination consisted of the following procedures : 1. Visual acuity determination. The visual acuity was tested at a 6-meter distance, using the Snellen linear illiterate E chart (fig. 3 ) . The native interpreter proved invaluable, in this as well as in other phases of the examination, in helping the subjects to understand and perform the tests.
Fig. 2 (VerLee). Examination facilities on Bougainville. The walled-off area at the extreme right provided a darkened area for the ophthalmic examinations.
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307
Fig. 3 (VerLee). Testing the visual acuity of a Nasioi mother. A native boy who had attended mission school and had learned some English helped perform the tests.
2. External ocular examination. A general examination of the external eye and adnexa was performed, including evaluation of the conjunctiva, cornea, lids and lacrimal apparatus. Corneal arcus, common in these people, was subjectively graded in all examinees on a scale from 0 to 4. A grade of 0 was assigned when no trace of arcus could be seen with the naked eye on close scrutiny. A grade of 1 was given when the arcus was barely visible, whereas a grade of 4 indicated a wide, dense corneal band. An arcus whose size and density was intermediate between that of Grades 1 and 4, was assigned a grade of 2 or 3. Eversion of the upper lid was performed on all examinees, and the upper palpebral conjunctiva carefully examined. The loupe was used for further detailed examination only if pathologic findings were encountered upon inspection with the naked eye. The pupillary reaction to light, both consensual
and direct, as well as reaction to accommodation was noted. 3. Motility examination. Prior to atiministration of the cycloplegtc drug, examination of ocular motility was performed. This evaluation included ocular version movements, a prism and alternate cover test for heterophoria and heterotropia (with fixation maintained at a 6-meter distance), and near point of convergence (fig. 4 ) . 4. Refraction. Following the motility examination, the pupils of all subjects were dilated with 1% cyclopentolate hydrochloride using two drops in each eye. ( T o reduce the residual accommodation as much as possible, the use of 1% atropine sulfate eye drops had been considered, but because of uncertainties as to how the natives might react to prolonged paralysis of accommodation, cyclopentolate hydrochloride was substituted.) Because of the nature of the examination procedure, with the examinees visiting var-
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A U G U S T , 1968
Fig. 4 (VerLee). Testing the near point of convergence on a young Nasioi boy. A number on the left arm identified each subject for the study.
ious examiners at different times, the interval from dilation to retinoscopy could not be held constant, and therefore varied from 30 to 60 minutes. Using a battery-powered retinoscope, retinoscopy was performed with the subject fixing at six meters. In those subjects in which the visual acuity was 20/30 or poorer, a manifest (subjective) refraction was performed in addition to retinoscopy, to determine the best possible corrected visual acuity. 5. Fundus examination. Ophthalmoscopy was performed through a dilated pupil using a battery-powered direct ophthalmoscope. 6.. Tonometry. With the subject lying on a cot, one drop of 1% proparacaine hydrochloride was instilled into each eye. Intraocular pressure was determined with a Schip'tz tonometer using a 5.5 gm weight. T o maintain sterility as well as obviate the need for cleaning the tonometer, a sterile latex rubber tonometer footplate cover was used for each examinee. 7. Photography. All abnormal ocular findings were photographed using a 35 mm camera with close-up lenses, and a battery-powered electronic Hash unit. Abnormal fundi were photographed with a hand-held portable fundus camera fitted with a specially constructed wet cell battery power unit.
RESULTS AND COMMENTS
Due to lack of cooperation (usually because of young age) not all tests could be performed on all subjects and therefore the number of participants for the various examinations differs. 1. Visual acuity. The superb uncorrected visual acuity in 512 subjects is shown in Table 2. O f these 1,024 eyes, 93.2% demonstrated a visual acuity of 20/20 or better, and 95.3% of all 512 subjects had a visual acuity of at least 20/20 in the better eye. In only 24 eyes was the visual acuity 20/40 or poorer ; these 24 eyes, all of which occurred in fully grown subjects (over 15 years old) are shown in Table 3. The vision in eight of these eyes could be improved to 20/30 or better with correction of a refractive error, and an additional 13 showed pathologic conditions which could account for the decreased visual acuity. There were only three eyes (all with visual acuity of 20/50) in which the acuity could not be improved with refraction or in which no pathologic condition could be demonstrated which might account for the decreased acuity. If the 13 eyes with pathologic changes are excluded, 94.5% of all eyes, and 96.3% of the better eyes in each subject, had uncorrected visual acuity of 20/20 or better.
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SURVEY IN TABLE
SOLOMON
ISLANDS
309
2
V I S U A L ACUITY I N 5 1 2 SUBJECTS
All 1024 Eyes Visual Acuity 20/15 20/20 20/30 20/40 20/50 20/100 20/200 20/400 Finger counting Light perception N o light perception Total
Better Eye Only (512 Eyes) by Age Groups (yr)
%
No.
No.
0-14
15+
. Total No.
%
No.
%
263 72 16 2 3 0 0 1 0 1
73.4 20.1 4.5 0.6 0.8 0.0 0.0 0.3 0.0 0.3
396 92 17 2 3 0 0 1 0 1
77.3 18.0 3.3 0.4 0.6 0.0 0.0 0.2 0.0 0.2
%
769 186 45 4 11 1 2 2 0 2
75.1 18.1 4.4 0.4 1.1 0.1 0.2 0.2 0.0 0.2
133 20 1 0 0 0 0 0 0 0
86.4 13.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2
0.2
0
0.0
0
0.0
0
0.0
1024
100.0
154
100.0
358
100.0
512
100.0
Excellent visual acuity has been reported in other societies which are unacculturated by Western standards. In his studies of Xavante Indians of Brazil, Neel found a binocular visual acuity of 20/15 or better in 12 of the 13 males on whom determinations were performed. He stated that, probably for cultural reasons, the females did not seem to be able to understand and perform the visual acuity test as well as the males. Neel also cites Mattos' study* of Xingu and 1
Xavante Brazilian Indians which showed binocular visual acuity of 20/15 or better in 55 of 77 (71.4%) males. Mann, " in her study of 145 Australian aborigines, found 126 (86.9%) with a binocular visual acuity of 6/6 or better, even though many had trachoma of varying degrees. Several had phenomenal visual acuity, two described as having 17/5. Studies performed on Western population groups, on the other hand, suggest a s
a
TABLE 3 DESCRIPTION OF THE 24 EYES WITH VISUAL ACUITY OF 2 0 / 4 0 OR POORER
Number of Eyes Not Correctable to 20/30 or Better Visual Acuity
Correctable to 20/30 or Better*
Senile Cataract
Corneal Opacities
Macular Changes
Traumatic Cataract
Phthisis Bulbi
No Explanation Found for Decreased Acuity
Total No. of Eyes
20/40 20/50 20/100 20/200 20/400 Light perception N o light percpetion
1 6 1 0 0 0
0 2 0 2 2 0
2 0 0 0 0 0
1 0 0 0 0 0
0 0 0 0 0 2
0 0 0 0 0 0
0 3 0 0 0 0
4 11 1 2 2 2
0
0
0
0
0
2
0
2
Total
8
6
2
1
2
2
3
24
1
With manifest refraction.
310
A U G U S T , 1968
AMERICAN JOURNAL OF OPHTHALMOLOGY TABLE 4 DISTRIBUTION OF REFRACTIVE ERRORS IN 1155
EYES
Cylindrical Error (Diopters) Number of Eyes +0.25 +0.50
•a a
PI
o •a
+ 2 50 + 2 25 + 2 00 + 1 75 + 1.50 +1.25 +1.00 +0.75 +0.50 +0.25 +0.00 -0.25 -0.50 -0.75 -1.00 -1.25 -1.50
+0.75 +1.00 +1.25 +1.50 +1.75 +2.00 +2.25
+2.50
1 6 1 25 17 71 58 251 159 67 1 2
2 1 21 17 42 54 27 3 2
5 3 22 12 86 109 23 4 2
1 2 1 12 3 8
1094 "spherical" eyes (94.7%)
61 "nonspherical" eyes (5.3%)
much smaller proportion of the general population with such excellent uncorrected visual acuity. In Sorsby's study of 1,033 British recruits, only 67.7% had visual acuity of 6/6 in the better of the two eyes. Karpinos obtained data on the visual acuity of 273,000 recruits, and found that 82% of the Negroes 6
7
and 69% of the Caucasians had uncorrected binocular visual acuity of 20/20 or better. 2. Refractive errors. The distribution of the refractive errors in 1,155 eyes (representing 581 individuals) in which retinoscopy could be performed is shown in Table 4. The eyes are divided into two groups,
TABLE 5 DISTRIBUTION OF REFRACTIVE ERRORS IN 1,155
Refractive Error (Diopters) +2.50 +2.25 +2.00 +1.75 +1.50 +1.25 +1.00 +0.75 +0.50 +0.25 +0.00 -0.25 -0.50
"Spherical" Eyes* ( < 0 . 5 D Cylinder) No.
%
EVES
"Non-Spherical" Eyesf ( > 0 . 5 D Cylinder) No.
%
Total No.
1 0 6 8 29 60 100 186 414 209 74 5 2
0.1 0.0 0.5 0.7 2.7 5.5 9.1 17.0 37.8 19.1 6.8 0.5 0.2
0 0 0 0 2 2 6 2 24 6 16 1 2
0.0 0.0 0.0 0.0 3.3 3.3 9.8 3.3 39.3 9.8 26.3 1.6 3.3
1 0 6 8 31 62 106 188 438 215 90 6 4
1094
100.0
61
100.0
1155
* Spherical equivalent (sphere+0.50 cylinder), t Less ametropic meridian.
% 0.1 0.0 0.0 0.7 2.7 5.4 9.2 16.3 37.9 18.6 7.8 0.5 0.3 100.0
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spherical and nonspherical, following the convention used in other studies - which consider eyes with a cylinder of 0.5 diopter or less to be spherical and those with greater than 0.5 diopter, nonspherical or astigmatic. The distribution of refractive errors is summarized in Table 5 and Figure 5, in which the spherical equivalent (sphere +0.50 cylinder) is used for the spherical eyes, and the less ametropic meridian for the nonspherical eyes. In general, this analysis follows the format used by Sorsby* in his recent study of British subjects. Two significant observations can be made from these data. First, only a very small number of eyes (10 of the 1,155 eyes, or 0.8%) were myopic, none by more than 0.5 diopter ; and second, relatively few eyes had substantial amounts of astigmatism, only 61 eyes (5.3%) having 0.75 of a diopter or more. A s can be seen, the great majority of the eyes fall in the lower degrees of hyperopia, with over 98% of all eyes having from 0 to 2 diopters of hyperopia. This undoubtedly does not reflect the true distribution of the hyperopic eyes, since cycloplegia was not complete. Incomplete cycloplegia, however, should have no effect on the distribution of the myopic eyes. 9
The
311
OPHTHALMIC SURVEY IN SOLOMON ISLANDS
9
astigmatism of 0.75 diopter or more
found in 61 eyes was mostly of low degree, with only 13 (21.3%) having greater than 1 diopter. Figure 5 illustrates that the astigmatic eyes were fairly evenly distributed over the range of spherical errors. The rarity or absence of myopia and astigmatism has been shown in two excellent studies of non-Western societies, those of Holm and Skeller. Holm, in his study of African Negroes, reported myopia in only 14 (0.3%) of 4,926 nonselected eyes. Two of these 14 eyes had myopia of 0.5 diopter, with the other five ranging from 3 to 9 diopters. Of these 4,926 eyes, only 42 (0.9%) had astigmatism of greater than 1 diopter. Skeller's study of refractive errors in 1,450 eyes of all Angmassalik Eskimos in Greenland showed only 1% to be myopic, all of which were less than 1.5 diopters. However, 292 of the 1,450 eyes (20.1%) had astigmatism of greater than 0.5 diopter; 183 ( 12.6% ) had greater than 1 diopter. It also has been reported that the frequency of myopia is low or nonexistent in American Indians, "* Australian aborigines, " and the Polynesians of Samoa. The low frequency of myopia in these population groups is in contrast to the higher frequencies reported in studies of Western populations. Two such studies, dealing with 8
9
5
5
0
10
40 T o t a l height * all eyes EZ%3 "Non-spherical" eyes 30 Fig. 5 (VerLee). Distribution of refractive errors in 1,155 eyes. Plotted by spherical equivalent (sphere + 0.50 cylinder) for eyes with 0.5 diopter or less cylinder ("spherical" eyes), and by the less ametropic meridian for eyes with greater than 0.5 diopter cylinder ("nonspherical" eyes).
I
I "Spherical" eyas
¡3
>U
20
u e in O.
10
-
T~—I—"
I
"—I— —I—'—I— —I 1
1
•
I
•
I
I
O.90 0.25 -04- 025 OSO 0.7S 1.00 I.2S 1.50 1.75 2.O0 225 2 5 0 R E F R A C T I V E E R R O R (diopters)
312
AMERICAN JOURNAL OF OPHTHALMOLOGY
A U G U S T , 1968
TABLE 6 HETEROTROPIA—•DISTRIBUTION OF 13 CASES FOUND IN 616 SUBJECTS No. of Cases
Measurement*
Age Range (vr)
Mean Age (vr)
Comitant deviations Intermittent exotropia Intermittent exotropia Constant exotropia Intermittent esotropia
S 5 1 1
D>N N>D D=N N>D
22^7 27-63 50 13
33.4 45.2 50.0 13.0
Noncomitant deviation Paresis of third cranial nerve
1
51
51.0
Type of Deviation
* D > N indicates that the deviation while fixing at distance (6 meters) is greater by 10 prism diopters or more than while fixing at near (1/3 meter). Conversely, N > D indicates the near deviation is greater by 10 prism diopters or more than the distance deviation. D = N indicates that there is less than 10 prism diopters difference between the distance and near deviations.
relatively unselected material, include those of Sorsby and Stromber. In Sorsby's study of 2,066 eyes of British recruits, 11.0% were myopic; the myopia was greater than 1.0 diopter in 6.6% of all eyes. Astigmatism of greater than 0.5 diopter was present in 18.7%. In Stromberg's study of 5,122 eyes of Swedish conscripts, myopia was present in 8.86% and was greater than 1 diopter in 3.4%. Schepens and Marden have recently summarized data on the frequency of myopia. Most of their studies deal with eye patients and therefore represent selected material, but the studies indicate an overall incidence of myopia from 5% to 18% in European and American populations. These authors also cite studies of Chinese and Japanese which suggest an even higher frequency of myopia in these groups. 3. Ocular motility. A. Heterotropia Binocular eye movements (versions) were normal in all 616 subjects except one in whom a noncomitant (paretic) deviation was encountered. This was a 51-year-old woman who stated she had had drooping of the left eyelid for many years. On examination, the left palpebral fissure was 3 mm less than the right, with the left eye displaced interiorly and temporally. There was limitation of elevation and adduction, but the pupillary reactions to light and accomodation were intact. 8
11
12
A probable diagnosis of left third cranial nerve paresis was made. Cover testing on the 616 subjects revealed 12 cases (1.9%) of comitant heterotropia (table 6 ) , of which only one was constant—a case of exotropia measuring approximately 15 prism diopters for both distance and near in a 50-year-old man. Of the 10 intermittent exotropia cases, five had at least 10 prism diopters greater deviation for distance than for near (divergence-excess type) and occurred in a relatively young age group (mean age 33.4 years). The other five cases of intermittent exotropia, all of which had at least 10 prism diopters greater deviation for near than for distance (convergence-insufficiency type), occurred in a relatively older age group (mean age 45.2 years). Esotropia was considerably less common than exotropia, with only one case (0.2%) found in the 616 subjects. This case, in a 13-year-old girl, demonstrated two prism diopters of esophoria at distance, and a variable amount of esotropia (8-15 prism diopters) at near. Mann * stated that esotropia has been reported absent or rare in the Melanesians of New Guinea, Fiji, and New Britain; it has also been found rare in the people of Southeast Asia, in Indians of North and South America, Australian aborigines, and some tribes in Africa. She also stated that, unlike esotropia, exotropia seems universally dis5
d
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and may not be representative of the general population. Further, comparison of such results are difficult because of the different methods used for measuring heterophoria. studying Thus, Grieve and Archibald, 1,209 healthy adult (age I7yi to 30 years) males with no high refractive errors, used the Maddox wing, and found 184 (15.2%) with greater than six prism diopters of exophoria. Eight of the 1,209 (0.7%) had more than six prism diopters of esophoria. Young in studying 905 refraction patients, found that 18.5% had greater than eight prism diopters of exophoria as measured with the Maddox rod. It should be noted that in both studies, unlike the present one, measurements were performed at near. Nevertheless, this data would suggest a wider spread of heterophoria values in Western groups than in the present study.
tributed throughout the world, although the frequency is also low. Available statistics in Western societies, usually from studies performed in schoolage children, suggest a frequency of comitant strabismus from 1% to 2%. In the present study, if the 262 children aged 14 years or under are considered separately, the only case found in this age group places the frequency at 0.4%. This would suggest, at least in children, that strabismus is less common in Melanesian societies than in Westernized cultures.
14
13
15
B. Heterophoria The results of alternate cover testing of the remaining 604 subjects are shown in Table 7. The majority (93.6%) of subjects had orthophoria or an exophoria ranging from 1 to 8 prism diopters. Only 3% had more than 8 prism diopters of exophoria and only 3.4% had esophoria, less than 6 prism diopters in all cases. The breakdown by age indicates there was a general increase in exophoria with increasing age. Accurate statistics on the distribution of heterophoria in Western societies are difficult to obtain because the few such studies performed have used selected case material,
C. Near-point of convergence The distribution of the near-point of convergence ( N P C ) determinations for the 573 subjects participating in this test is shown in Table 8. As might be expected, there is a tendency toward less convergence ability in the older age groups. Just under 50% of subjects 30 years of age or older had an
TABLE 7 D I S T R I B U T I O N O F H E T E R O P H O R I A I N 604
SUBJECTS*
Age (yr) Heterophoria (Prism d,opters)
4
N
q
%
N
o
%
N
q
5
+
T
%
N
q
°'
a l
%
5-6 3-4 1-2 0
0 5 2 160
0.0 2.1 0.8 65.8
1 8 2 73
0.4 3.1 0.8 27.9
0 2 0 18
0.0 2.0 0.0 18.2
1 15 4 251
0.0 2.5 0.7 41.6
1-2 3-4 5-6 7-8 9-10 11-12 13-14 15
18 31 21 6 0 0 0 0
7.4 12.8 8.6 2.5 0.0 0.0 0.0 0.0
28 64 65 12 5 1 2 1
10.7 24.3 24.7 4.6 1.9 0.4 0.8 0.4
6 22 27 15 6 2 1 0
6.1 22.2 27.2 15.2 6.1 2.0 1.0 0.0
52 117 113 33 11 3 3 1
8.6 19.4 18.7 5.5 1.8 0.5 0.5 0.2
243
100.0
262
100.0
99
100.0
604
100.0
Total
* Measured by alternate cover testing with fixation at 6 meters.
A U G U S T , 1968
AMERICAN JOURNAL OF OPHTHALMOLOGY
314
TABLE 8 NEAR POINT OF CONVERGENCE (NPC) IN 573 SUBJECTS Age (yr) NPC (mm.)
30-49
0-29 No.
50+
Total
%
No.
%
No.
%
No.
%
77 0 0 6 48 20
51.0 0.0 0.0 4.0 31.8 13.2
33 0 0 5 23 9
47 .1 0 .0 0 .0 7 .1 32 .9 12 .9
351 1 0 31 152 38
61.3 0.2 0.0 5.4 26.5 6.6
151
100.0
70
573
100.0
0 5-24 25-49 50-99 100-199 200 +
241 1 0 20 81 9
68.5 0.3 0.0 5.7 23.0 2.5
Total
352
100.0
NPC of 100 mm or more ; this was found in only 25.5% of those under the age of 30 years. 4. Tonometry. The distribution of intraocular pressure determinations as measured with the Schip'tz tonometer for 812 of the 814 eyes in which Schip'tz determinations could be performed is shown in Figure 6. Not included in this distribution are two eyes (one from each of two subjects) with traumatic injuries and elevated intraocular pressure thought to be secondary to the injury. The intraocular pressure in the fellow eye in each of these two cases was within normal limits. Plotted on the graph (fig. 6 ) is the percent of eyes for each of the scale readings on the Schätz tonometer. Also shown is the equivalent pressure in mm Hg (1955 revision of the Schip'tz conversion table) and the number of eyes for each of the scale readings.
100 .0
The mean intraocular pressure in the 812 eyes was 15.97 mm Hg with a standard deviation of ±2.24. Only three eyes (0.4%) were encountered with intraocular pressures greater than 21 mm Hg, the figure sometimes used in Western populations to represent the upper limit of normal for the majority of the population. The intraocular pressure in each of these three eyes was 22.4 mm Hg, only slightly higher than this upper limit. 18
Many studies of the distribution of intraocular pressure in Western populations have been undertaken, five of which are summarized in Table 9, together with data from the present study. It is evident that the mean intraocular pressure for all these studies does not vary greatly, but the standard deviation of the present study is smaller than those of Western populations, indicating a smaller spread of values. 17-20
Fig. 6 (VerLee). Distribution of Schätz intraocular pressure determinations in 812 eyes.
SCHIOTZ SCALE READING
7.S 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5
EQUIVALENT PRESSURE (mm-Ho.) 11.2
12.2 13.4 14.6 15.9 17.3 18.9 20.6
22.4
NUMBER OF EYES
84
3
8
77
123 182 209 79
45
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66, N O . 2
OPHTHALMIC
SURVEY
IN SOLOMON
TABLE COMPARISON OF TONOMETRIC DATA WITH
Author
Location
Age Range (yrs.)
315
ISLANDS
9
THAT OF W E S T E R N POPULATION
T y p e of Study
No. of Subjects
No. of Eyes
Method
GROUPS Intraocular Pressure (mm Hg)
Mean
S. D .
Distribution Curve
Leydbecker and assoc. (19S8) Graham and Hollows (1964)
Bonn, Germany South Wales Wales
6-70
self-selection
10,000
19,880
Schifitz
15.50
2.57
skew
40-74
total community
4,246
8,492
Schitftz
15.1
2.90
skew
Armaly. M . L. (1965) Schwartz and assoc. (1966) Bankes. J * and assoc. VerLee. D . L. (present study)
Des Moines, Iowa Nesquehoning. Pa. Bedford, England Solomon Islands
20-89
sample
2,327
4,652
Applanation Applanation
15.9 16.85
2.86 3.75
skew skew
25-70 +
total community selfselection total community
1,004
Schätz
15.24
3.34
skew
5,941
11,849
Schi0tz
16.29
3.43
skew
Schitftz
15.97
2.24
no skew
40
+
3-79
502
407
812
* Bankes. J., Perkins, E. S.. Tsolabis, S. and Wright. J. E.: The Bedford Glaucoma survey. (Unpublished data.)
The distribution of intraocular pressure in the studies of Western population groups listed in Table 9, as well as in other studies, show a skew toward higher pressure readings which has been interpreted by some to indicate the presence of a separate "glaucoma population." The absence of such a skew in the present study is shown most clearly when the distribution of intraocular pressures is plotted on a cumulative frequency graph (fig. 7 ) . On this graph is plotted the distribution of intraocular pressures and a straight line. The straight line is based on the mean and standard deviation of the sample, and represents a "normal" (Gaussian) distribution. On such a graph, a skew of the type occurring 17
in the studies " above, would be repre-sented by an upward curve (dotted line) of the plotted points above the normal line. As is evident from the graph, the values plotted in the present study show no such tendency. No signs of advanced glaucoma (cupping of the optic nerve head or gross visual field loss) were found. This observation, together with the absence of an upward skew in the distribution of intraocular pressures and the fact that in only three eyes was the pressure as high as 22.4 mm Hg, suggests that chronic simple glaucoma is rare or nonexistent in this population. On the basis of surveys, chronic simple glaucoma likewise has been reported rare or absent in natives in New Guinea and 17
20
316
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A U G U S T , 1968
T A B L E 10 CORNEAL ARCUS IN 618 SUBJECTS Age (yr) Arcus Grade
0-14
0 1 2 3 4 Total
15-39
%
No.
%
No.
%
No.
%
186 53 4 1 1
75.9 21.7 1.6 0.4 0.4
123 73 28 3 0
54.2 32.2 12.3 1.3 0.0
39 46 31 19 11
26.7 31.5 21.2 13.1 7.5
348 172 63 23 12
56.4 27.8 10.2 3.7 1.9
245
100.0
227
100.0
146
100.0
618
100.0
21
22
10
8
5
5
8
23
5
Total
No.
Papua, the Maoris of New Zealand, the Polynesians of Niue and Samoa, as well as natives of Tristan de Cunah in the South Atlantic, " the Cocos Kieling Islands in the Indian Ocean, "' in Australian Aboriginies, " and Indians of North and South America. " 5. Corneal arcus. The distribution of arcus, graded as previously described, is shown in Table 10. Arcus in these people is very common ; it was present in some degree in 43.6% of all 618 subjects on whom an external examination could be performed. The breakdown of subjects by age in Table 10 reveals an increased frequency of arcus in the older age groups. The majority (73.3%) of subjects aged 40 years and over had some degree of arcus, whereas this was true in only 45.8% of those aged 15 to 39 years. These findings, using the KolmogorovSmirnov test, were significantly different (p<.001). Moreover, arcus was not only more common, but also more severe in the older age groups. Of those 40 years old or more, 41.8% had an arcus graded as 2 or greater, whereas an arcus of this degree occurred in only 13.6% of those in the 15- to 39-year-old age group, and in only 2.4% of those 14 years of age or under. As concerns the pigmented races, arcus is said to be common in Indonesians of tropical areas and more common in Negroes than in whites in North America. * * In Caucasians there is a steady rise in the fre8
40 +
11
24
25
2
quency of arcus with increasing age, but there seems to be also an association of arcus with abnormalities of lipid metabolism. Hypercholesterolemia, particularly in the familial type and in younger individuals, shows such a relationship, but this is by no means consistent. A relationship between abnormalities of lipid metabolism and arcus has also been demonstrated recently in young (aged 30-45 years) Negroes, showing a positive correlation between serum cholesterol and phospholipid levels and the degree of arcus. Serum cholesterol determinations were performed in the present study and the preliminary evaluations of the association of the degree of arcus with the serum cholesterol level did not appear to indicate a significant relationship. This relationship will be evaluated more fully in a future publication. 27
27
28
6. Pathologic conditions. The pathologic conditions observed on external and ophthalmoscopic examinations are listed in Table 11. A s can be seen, the predominant conditions found were of infectious and traumatic etiology. In a population prone to infections thought to be associated with uveitis (for example, tuberculosis and leprosy), only three cases of uveitis (all chorioretinitis) were observed. No case of anterior uveitis was encountered. The healthy appearance of the retinal vessels in older individuals was remarkable. The only case of hypertensive retinopathy encountered occurred in a man whose blood pressure was 180/120, and was
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O P H T H A L M I C S U R V E Y IN
thought to be on the basis of renal disease. Diabetic and arteriosclerotic retinopathy were nonexistent in the study subjects. In view of the widespread trachoma throughout much of the South Pacific, it is noteworthy that no trachoma was seen in the study population. Many cases of trachoma were seen, however, during the course of operating a daily clinic in both Malaita and Bougainville for natives living in the offshore islands and nearby coastal areas. The presence of trachoma in these persons but not in the study population is of interest from an epidemiologic standpoint ; no explanation was evident for this observed difference, except possibly the higher altitude and the relative social isolation of the study population from the coastal natives. It is probably of little value to attempt comparisons of the frequencies of the pathologic conditons listed in Table 1 with the frequencies reported in Western populations, since the number of involved individuals is very small, and accurate figures of the prevalence of these conditions are not available for Western populations. In addition, in Western populations, varying criteria are used for diagnosis, making valid comparisons difficult. CONCLUSIONS
It should be stressed that valid comparisons between data of the present study and samples of Western population groups are difficult because characteristics of the samples differ and different examining methods are used. Nevertheless, even taking these factors into account, the present study, as well as other studies, strongly suggests that many biologic differences exist between Western societies and those societies unacculturated by Western standards. Mam' characteristics of such peoples, of course, such as the prevalence of infectious diseases, clearly are due primarily to environmental factors. Other characteristics, particularly the relative rarity of chronic and degenerative diseases,
S O L O M O N
317
I S L A N D S TABLE
11
PATHOLOGIC CONDITIONS
ENCOUNTERED*
No. of Cases General phthisis bulbi traumatic injuries with peripheral anterior synechiae and secondary glaucoma Eyelids tinea imbricata external hordeolum sebaceous cyst fusion of temporal aspects of upper and lower lids, probably traumatic
2 2 1 1 2 1
Cornea and Conjunctiva inspissated mucus, palpebral conjunctiva conjunctivitis, purulent conjunctivitis, follicular conjunctival nevus, large cornea, opacities—traumatic and infectious Trantas spot pterygium Pinguecula, prominent
S 1 2 2
Lens cataract, traumatic cataract, senile posterior lenticonus
3 4 1
Vitreous asteroid hyalosis prominent hyaloid remnants
2 4
Choroid and Retina chorioretinitis, active chorioretinitis, healed, inactive drusen, diffuse, involving posterior pole hypertensive retinopathy
1 2 5 1
2 3 1 3
* Ametropias and heterotropias excluded.
most likely are a result of interplay of environmental and genetic factors. On the basis of family and twin studies, many biologic characteristics—for example, errors of refraction—have been found to be strongly influenced by heredity. It therefore seems reasonable to suppose that differences in the racial distribution of these characteristics are also best explained on a genetic basis, possibly through the mechanism of natural selection. For example, relaxation of selection as a result of diminished need for acute distance visual acuity by Western populations, may allow the genes contributing to myopia to be perpetuated. The role of the environment, however, must remain an open
318
AMERICAN JOURNAL OF OPHTHALMOLOGY
question. A s these population groups become more acculturated, one might expect that, unlike the many years usually necessary for genetic changes produced by natural selection to occur, biologic characteristics associated with a change in environment would manifest themselves in a relatively short period of time. For example, if myopia can result from close work, one would expect that as these people learn to read and become engaged in other tasks requiring an increasing amount of time spent with the eye in the accommodated state, the frequency of myopia in the population would increase, becoming evident in, genetically speaking, a relatively short time. Either the presence or absence of such findings would do much to increase our knowledge of the pathogenesis of many such conditions. It is hoped that insight into the relative influence of hereditary and environmental factors in the production of ocular characteristics can be gained by future investigations. SUMMARY
An ophthalmic survey of two native population groups in the Solomon Islands was performed as part of an initial complete medical and anthropologic investigation of these populations. Included in the ophthalmic examination was the evaluation of visual acuity, external disease, ocular motility, refraction, ocular fundus, and intraocular pressure. Among the observations made were the following, which are of particular interest because they differ from data on Western populations: 1. Approximately 95% of all persons had visual acuity of 20/20 or higher in the better of the two eyes. 2. Refractive errors, in particular myopia and astigmatism, were rare. Only 10 of the 1,155 (0.8%) eyes were myopic, and the myopia in all 10 was 0.5 diopter or less. A s tigmatism of 0.75 diopters or more was found in only 61 ( 5 . 3 % ) of the eyes. 3. Schätz tonometry determinations re-
A U G U S T , 1968
vealed only three of 812 eyes to have intraocular pressures over 21 mm H g ; the pressure in all three was 22.4 mm Hg. 4. Arteriosclerotic and hypertensive retinopathy were virtually absent in all age groups. ACKNOWLEDGMENTS
Grateful acknowledgment is given to Dr. J. Theodore Schwartz, Head, Section on Ophthalmic Field and Developmental Research, Epidemiology Branch, N I N D B , for his constructive suggestions both in preparation of the protocol and for evaluation of the manuscript, and to Mr. Allen R. Lewis, Office of Biometry, N I N D B , for his help in preparing and carrying out the statistical analysis of the data. REFERENCES 1. Neel, J. V., Salzano, F. M., Junqueira, P. C, Keiter, F. and Maybury-Lewis, D. : Studies on the Xavante Indians of the Brazilian Mato Grosso. Am. J. Hum. Genet 16:52,1964. 2. Niswander, J. D. : Further studies on the Xavante Indians. V I I . The oral status of the Xavantes of Simôes Lopes. Am. J. Hum. Genet 19:543, 967. 3. Lowenstein, F. W . : Blood pressure in relation to age and sex in the tropics and subtropics. Lancet 1:389, 1961. 4. Mattos, R. B. : Acuidade visual para longe a frequência de discromatopsia em indios brasileiros. Arq. Brasil. Oftal. 21:105, 1958. Cited by Neel* 5. Mann, I . : Culture, Race, Climate and Eye Disease. Springfield, III, Thomas, 1966. (a) p. 466, ( b ) p. 544, ( c ) p. 44, (d) p. 553, (e) p. 37, ( f ) p. 45, ( g ) p. 468, (h) p. 483. 6. Sorsby, A., Sheridan, M., Leary, G. A . and Benjamin, B. : Vision, visual acuity, and ocular refraction of young mea Brit Med. J. 1:1394, 1960. 7. Karpinos, B. D. : Racial differences in visual acuity. Public Health Rep. 75:1045, 1960. 8. Hohn, S.: Les états de la réfraction oculaire chez les Palénegrides au Gabon, Afrique Êquatoriale Française. Acta Ophth. Suppl. 13:1, 1937. 9. Skeller, E. : Anthropological and Ophthalmological Studies on the Angmagssalik Eskimoes. Meddelelser om Grönland, Copenhagen, C. A . Reitzels Forlag, 1954, p. 107. 10. Loschdorfer, J. : General Survey of Eye Diseases in Niue Island, American Samoa and Western Samoe. Technical information circular No. 13. South Pacific Commission, August 1955. 11. Stromberg, E. : Über refrakion and achsenlange des menschlichen auges. Acta Ophth. 14:281, 1936. 12. Schepens, C. L. and Marden, D. : Data on the natural history of retinal detachment Am. J. Ophth. 61:213,1966. 13. Duke-Elder, S.: Text-book of Ophthalmology, S t Louis, Mosby, 1949, vol. 4, p. 4004. 14. Grieve, J. and Archibald, D. H . : Some facts and figures relating to heterophoria in symptom-
V O L . 66, N O . 2
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OF THE
CORNEA
TIBOR G . FARKAS, M . D . AND JAMES P . ZNAJDA, M . D . Chicago, Illinois
Hypertrophic scars of the cornea are quite uncommon. Since Szokalski first described a case of corneal keloid in 1865 only 40 additional cases have been reported in the literature. In 1940, Smith collected 37 cases in his literature review. In 27 of these cases, disease, surgery or injury preceded the formation of the corneal mass. Two theories have been proposed to explain the formation of corneal keloids. Parsons, in 1904, and then Fuchs, in 1918,* suggested that they originated from the stromal cells of the iris. Fenton and Tredici, in 1964, proposed that they formed from proliferating fibrovascular tissue during the healing stage of corneal perforation. Recently we examined a corneal keloid which ap1
2
peared to support Parson's and Fuchs' suggestion that corneal hypertrophic scars originate from the iris. CASE REPORT A white female infant, first seen by us when she was three months old, had had a protruding corneal
3
5
From the Eye Research Laboratories, University of Chicago. This study was supported in part by U S P H S Grants NB-3358 and FR-55 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland.
Fig. 1 (Farkas and Znajda). Gross specimen showing iris prolapsing through the corneal perforation. ( x 5 . )