A High Prevalence of Occludable Angles in a Vietnamese Population

A High Prevalence of Occludable Angles in a Vietnamese Population Ngoc Nguyen, MD,l Justin S. Mora, FRACO,1,2,3 Michelle M. Gaffney, COMT,l Albert S. Ma, BS,l Patricia C. Wong, MD/ Andrew G. Iwach, MD,1,2,3 Henry Tran, MS,l Christopher J. Dickens, MDl Purpose: To assess the prevalence of occludable angles in a Vietnamese population. Methods: The authors retrospectively reviewed the angle status in 482 Vietnamese patients who presented to a general ophthalmology practice. All angles were graded by a glaucoma specialist according to the Shaffer method. Patients were excluded if they had known glaucoma or narrow angles, or a history of trauma or intraocular surgery. Results: A total of 29.5% of all patients surveyed and 47.8% of those 55 years of age or older had grade 0 to 2 angles. In the Framingham study, 3.8% of white patients 55 years of age or older had grade 0 to 2 angles. 1 Of the patients in our study population, 8.5% had grade 0 to 1 angles and were considered at high risk for occlusion. Conclusions: Vietnamese patients have a much higher prevalence of narrow angles and a greater risk of angle-closure glaucoma than white patients. Ophthalmology 1996; 103: 1426-1431

It is well known that, among white patients, the incidence

of primary angle-closure glaucoma (PACG) is much lower than that of primary open-angle glaucoma (POAG).1-5 However, this phenomenon is not common to all racial groups, with numerous epidemiologic studies demonstrating that some races have a much higher incidence of PACG than is encountered in the typical North American, European, or Australasian ophthalmic practice. 6 - 22 With changing patterns of immigration, it is essential that we are familiar with the different disease patterns displayed by various racial groups. In this article, we report on the angle status of a large Vietnamese group that now resides in the United States. To our knowledge, no data have been published regarding the configuration and depth of the Vietnamese angle. The purpose of this study is to determine whether there is a Originally received: June 22, 1995. Revision accepted: May 22, 1996. I Glaucoma Research and Education Group, San Francisco. 2 Glaucoma Research Foundation, San Francisco. 3 University of California, San Francisco, San Francisco. Reprint requests to Ngoc Nguyen, MD, Glaucoma Researth and Education Group, 490 Post St, Suite 622, San Francisco, CA 94102.

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significantly higher proportion of narrow angles and a greater risk of P ACG within this population.

Methods A retrospective study was undertaken within the practice of a fellowship-trained, glaucoma specialist (NN) who runs a glaucoma and comprehensive ophthalmology practice in an area with a large Vietnamese population. The following data were collected from 505 consecutive Vietnamese patients who presented for the first time for a general eye examination: age, sex, the reason for the visit (e.g., routine check, refraction, etc.), visual acuity, intraocular pressure (lOP), optic disc status, gonioscopy findings, and, as it was available, the refraction. A Zeiss gonioscopy lens (Carl Zeiss, Oberkochen, Germany) was used to examine the angle in all the patients. The following features were noted: (1) the Shaffer grading in four quadrants (superior, inferior, nasal, and temporal), (2) angle pigmentation, and (3) any angle peculiarities such as prominent iris processes or an unusual iris insertion. If the angle was very narrow, compression gonioscopy was used to determine whether any peripheral anterior synechiae were present.

Nguyen et al . Occludable Angles in a Vietnamese Population

T able 1. Complaints Leading to Ophthalmology Assessment Chief Symptom

No. of Patients

Blurred vision/suspected cataract Irritated or dry eye(s) Watery eye(s) Red Eye(s)/conjunctivitis Lid problem: e.g., chalazion, ptosis, dermatochalasis Pingueculum/pterygium Routine check/screening eye examination Ocular trauma Aching eye(s) Floaters Other symptoms

135

63

43 41 39 38 35 23 20 14 35

Data were evaluated for the right eye only. Patients with a known history of glaucoma or narrow angles were excluded, as were those with a history of intraocular surgery or trauma to the right eye. A presentation with an injury to the left eye was not considered an exclusion criterion. One patient who presented with a painful, red eye, and was found to have PACG with an lOP of 60 mmHg, was excluded. In a small group of eyes, the angle grade varied from one quadrant to the next. For the four eyes in which three quadrants were considered one grade and the fourth another grade, the eye was assigned to the most common grade. For eyes that had two quadrants of one grade and two of another, half the eyes were assigned to one grade and half to the other. This division was age and sex matched. Eight eyes were in this category, and all of these were graded slit (n = 4) to 1 (n = 4). We believed this would give a more accurate description of the distribution of angle grades than would be obtained by arbitrarily assigning all the eyes to the lesser or greater grade.

Results Five hundred five patient charts were reviewed. Twentythree patients were excluded because of known narrow angles or glaucoma, or because of previous surgery or trauma to the eye. Of all the 482 remaining patients, gonioscopy data were available for all 482, visual acuities for 480 (2 patients had dementia, so visual acuities could not be obtained), optic disc status for 479 (the view of the posterior segment was obscured by cataract in 3 patients), lOP for 478, and refractions for 217. The principal symptoms leading to the visit to the ophthalmologist are listed in Table 1. Of those who presented with red eyes or sore eyes, one had a grade 1 angle with an lOP of 14 mmHg, one had an lOP of 26 mmHg with a grade 3 angle, and all others had angles of grade 2 or higher and an lOP less than 22 mmHg.

One hundred eighty-eight patients were men and 294 were women. The mean ages were 50 ± 18 years (range, 10-88 years) for men and 49 ± 17 years (range, 8-83 years) for women. Visual acuities ranged from 20/15 to hand motions: 20/20 or better in 192 patients (40%), 201 25 to 20/40 in 149 (31 %), 20/50 to 20/80 in 84 (17%), 20/100 to 20/400 in 36 (8%), and counting fingers or hand motions in 19 (4%). The principal causes for poor vision were cataract and age-related macular degeneration. None of the patients with advanced cataracts had secondary shallowing of the anterior chamber. The mean refractive error was -0.05 ± 3.25 diopters (D) (range, +9 to -26 D). The mean refractions were -2.0 ± 3.8 D for those with grade 4 angles, -0.7 ± 3.6 D for those with grade 3 angles, + 1.4 ± 2.2 D for those with grade 2 angles, and +0.7 ± 1.7 for those with grade 1 or less angles. There was a strong correlation between refractive error and age (P < 0.00001), with the mean refractive error increasing from a mean of - 2.28 for those 29 years of age or younger to +0.48 for those 70 years of age or older. The mean cup:disc ratio was 0.38 ± 0.19, which did not vary significantly with the angle grades. The mean lOP was 15.0 ± 3.6 mmHg (range, 6-42 mmHg). Of the 18 eyes with an lOP of more than 20 mmHg, 2 had grade 1 angles, 3 had grade 2 angles, and the remainder had grade 3 or 4. In .one patient with an lOP of 42 mmHg, POAG was diagnosed. The distribution of the angle grades is displayed in Table 2, both for the whole population and for males and females separately. Table 3 and Figure 1 show the distribution of angle grades according to age. Eight eyes had peripheral anterior synechiae in one or more quadrants. One of these eyes had an lOP of 28 mmHg, with peripheral anterior synechiae in one quadrant, a grade 3 angle, and a cup:disc ratio of 0.4. All the remaining eyes had an lOP less than 18 mmHg, and one had a slit angle, one a grade 1 angle, one a grade 2 angle, and four grade 3 angles. One eye had a closed angle with 360 of peripheral anterior synechiae, an lOP of 17 mmHg, and a cup:disc ratio of 0.9. Prominent iris processes were seen in five eyes; high iris insertions were not seen in any patients. Forty-two eyes had no angle pigmentation, 296 had light pigmentation, 136 had moderate pigmentation, and 8 had heavy pigmentation. 0

Table 2. The Distribution of Angle Grades by Sex Prevalence of Angle Grades (%) Shaffer Angle Grade

Total No. of Patients

Men

Wom en

O/closed Slit

0.2 4.4 3.9 21.0 55.2 15.3

0 2.7 4.3 20.7 52.1 20.2

0.3 5.4 3.7 21.1 57.2 12.3

1 2 3 4

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Ophthalmology

Table 3. Distribution of Angle Grades According to Age Prevalence of Angle Grades in Each Age Group (yrs) 70

29

30-39

40-49

50-59

60-69

Closed/O Slit 1 2 3 4

0% 0% 0% 4.6% 62.1% 33.3%

0% 0% 0% 11.9% 69.5% 18.6%

0% 0.8% 1.7% 21.4% 62.4% 13.7%

0% 5.0% 6.0% 23.0% 52.0% 14.0%

1.4% 8.5% 8.5% 23.9% 49.2% 8.5%

0% 11.6% 8.7% 37.7% 34.8% 7.2%

No. of patients

66

59

117

100

71

69

Angle Grade

:5

Discussion In white patients, POAG accounts for 75% to 95% of all glaucoma, with a prevalence of 0.5% to 2.1 %/-4 whereas PACG comprises approximately 6% of all glaucoma and occurs in 0.1 % of people older than 40 years of age. s However, in some racial groups the relative incidence of POAG versus PACG is reversed. The most well known and striking example of this is provided by the Eskimo popUlation. Alsbirk6 reported 10% of women and 2.1 % of men older than 40 years of age as positive to provocative testing, and a number of other population-based studies over several decades have shown incidences of PACG in Eskimos that are 20 to 40 times that of white patients. 7 - l2

;=:

There is great variation in the prevalence of PACG across the Asian continent. Research in Tibet has shown a low incidence of PACG (0.15% of those older than 40 years of age), 13 whereas in south Asia (India and Sri Lanka) the incidence is higher and is approximately comparable with that of PACG. 14•IS In east and southeast Asia, excluding Japan,16.17 all the racial groups that have been investigated (Chinese, Malaysian, Filipino, and Burmese l3 ) have been found to have a much higher ratio of PACG to POAG. Congdon et al 13 noted that, in one hospital-based Chinese series, angle closure comprised up to 94% of all primary glaucoma. One might expect an element of bias here because patients with symptomatic PACG may be more likely to present to the hospital,

Proportion of Vietnamese population with each angle grade

Figure 1. Angle grades according to age.

(%)

<30

30-39

40-49

50-59

60-69

Patient Age (years)

• Grade 0-1

1428

o Grade 2

llIGrade3-4

>69

Nguyen et al . Occludable Angles in a Vietnamese Population and, particularly in the poorer of these countries, a large proportion of open-angle glaucoma might go undetected. However, in a major Chinese study that used a populationbased rather than a hospital-based survey, the high prevalence persisted, with PACG affecting 1.3% of patients older than 40 years of age. IS Most research has focused primarily on the prevalence of angle-closure glaucoma rather than on the anatomy of the anterior chamber angle. Only five racial groups-whites, Eskimos, Africans, Tibetans, and Chinese-have had their anterior chamber angles graded in epidemiologic studies,13 some using the Shaffer method and some using van Herick gradings. Oh et al 5 have compared the angle configuration of African-American, white, and Far East Asian eyes. They did not specify the ethnic or national origins of the' 'Far East Asian" group. Despite the fact that there were more patients with myopia in the Asian group, and one might expect generally deeper angles, they found that their angular widths, as graded by the Spaeth system, were comparable to those of the African-American and white patients. They noted that the Asian eyes generally had a more anterior iris insertion, and they hypothesized that this might predispose them to progressive formation of peripheral anterior synechiae. More than 180,000 Vietnamese immigrants and refugees entered the United States from October 1991 to September 1994 (United States Immigration and Naturalization Service, Washington, DC). With this increasing immigration from Vietnam, particularly to the west coast of the United States, it is important to know the relative risk of angle closure within this population. The Vietnamese group we surveyed was derived from a general ophthalmology clinic and, inevitably, there is concern about selection bias when information is obtained from such a source. We have recorded the reason for the visit to the ophthalmologist's office and have excluded any patients who previously had had a diagnosis of any type of glaucoma and those who were known or suspected to have narrow angles on referral. Table 1 demonstrates that the patients presented with a variety of problems, few of which would be likely to preselect patients with narrow angle or PACG. Although there may be some selection bias, we believe the data reflect a clinical pattern in our local Vietnamese population. We chose the Shaffer system to analyze the angles in these patients because (1) the angle width is the key element in assessing the risk of angle closure and (2) this grading system is the one with which general ophthalmologists are familiar. The other factors to consider in the complete gonioscopic examination, but which are less important in this setting, are the degree of angle pigmentation, the contour and insertion of the iris, and the presence or absence of dense iris processes. In our Vietnamese population, we found a high prevalence of narrow and occludable angles. Of the Vietnamese patients, 37% were 40 years of age or older, and 47.8% of those 55 years of age or older had angles of grade 2 or less. Table 4 demonstrates that this prevalence of nar-

rower angles is dramatically higher than that of the Framingham Eye Study population of white patients by Leibowitz et all and approximately two thirds that of Eskimos.1 9 Angles were grade 1, slit, or closed in 11.5% of those 40 years of age or older and in 19.3% of those 60 years of age or older. These, particularly, are the patients who are at risk for angle-closure glaucoma. Our findings suggest an increased prevalence of narrow angles with increasing age (Table 3 and Fig 1), a factor that has been noted previously in white patients,I.23 Eskimos,19,20 Chinese,18,21 and Japanese. 16 However, the high female:male ratio of narrow angles that has been reported in white patients,2 black patients,22 Chinese,18 and Eskimos 7 was less apparent among the Vietnamese in our series (Table 2). In the 217 patients for whom refractions were available, the mean refraction was close to emmetropia. Hypermetropia increased with age (P < 0.00001), as did the prevalence of narrow angles, and there was a trend suggesting narrower angles with increasing hypermetropia. We cannot prove a relation between the two because the Shaffer grading system is an ordinal scale and we cannot statistically compare this with a numeric value (e.g., age or refraction). We did not see more crowded "hypermetropic" discs, with smaller cup:disc ratios, in the eyes with narrow angles. In how many of those patients with narrow angles will angle-closure glaucoma actually develop? In white patients, when there is a history of PACG in one eye, the risk of glaucoma developing in the other eye is as high as 50% to 75%.24-26 In the absence of contralateral glaucoma, the risk has been variously estimated between 7%24 and 37%.27 Wilensky et al 28 followed 129 patients with narrow angles or shallow anterior chambers for a mean of 2.7 years. They divided the eyes into two groups, depending on whether angle closure was considered possible on gonioscopic examination. Of those eyes that were potentially occludable on Zeiss or Koeppe gonioscopy (Ocular Instruments, Bellevue, W A), angle-closure glaucoma developed in approximately 12% within the follow-up period. Grade 2 angles are, in theory, capable of proceeding to closure, although this seldom occurs in white patients. 29 If these angles were included in Wilensky et aI's "occludable" group, one might expect their 12% figure to underestimate the number of grade 1 angles that ultimately will occlude. They found no single factor that accurately predicted which angles would occlude. Panek et al,27 through Cox's survival analysis, showed that patients with a higher lens thickness/axial length ratio tended to have peripheral iridectomies earlier (P = 0.03), and they suggested that this ratio might be a useful predictor of clinical outcome in patients with narrow angles. In Wilensky et aI' s28 study, nonacute angle closure developed in more than half of the patients, who were predominately white. This has been the experience of other investigators as well. 30,31 In black South Africans, two thirds of angle closure is chronic rather than acute or subacute. 22 Chinese and Singaporese also have been reported to have a high relative incidence of creeping angle closure. 32,33 Because it is asymptomatic, this is a significant cause of undetected visual loss in Chinese eyes. 33 It seems likely that creeping angle closure may be

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Ophthalmology Table

Volume 103, Number 9, September 1996

4. The Proportion of Eyes in Different Racial Groups with Angles Graded 2 or Lower by the Shaffer System

Authors

No. Eyes

Racial Group

Leibowitz et all Current study Drance et al zo Current study

5219 178 18 357

Whites Vietnamese Canadian Eskimos Vietnamese

a problem for the Vietnamese population also; therefore, it may be important to carefully follow those who have narrow angles to prevent gradual visual loss. Following this cohort of patients long term also will allow us to obtain clear data on the incidence of progression from narrow angles to angle closure glaucoma. In deciding whether to perform laser iridotomy in the presence of a narrow angle, patients must be treated on a case-by-case basis. Although laser iridotomy is a relatively benign procedure, careful consideration is necessary before performing the procedure because there are risks of inflammation, hemorrhage, cataract, posterior synechiae formation, lOP rise, and corneal bums and decompensation. 34,35 The following factors suggest that an iridotomy may be indicated: a history of halos; ocular aching or contralateral angle closure; the presence of glaucomflecken; glaucomatous cupping or an otherwise compromised disc; poor vision in the contralateral eye, for whatever reason; poor access to, or likely poor compliance with, acute ophthalmic care; and a particularly narrow angle. The role of provocative testing is controversial. There is a deficiency of population-based prospective information; therefore, it is difficult to assess the sensitivity and specificity of dark-prone, water-drinking, or mydriatic tests.13 In our opinion, the results of this survey cannot be extrapolated to include other Asian ethnic or national groups. Given the high prevalence of narrow angles in the study population, we believe it is important to assess Vietnamese patients carefully for narrow angles.

References 1. Leibowitz HM, Krueger DE, Maunder LR, et al. The Framingham Eye Study monograph: an ophthalmologic and epidemiologic study of cataract, glaucoma, diabetic retinopathy, macular degeneration, and visual acuity in a general population of 2631 adults, 1973-1975. Surv Ophthalmol 1980; 24(suppl):335-61 O. 2. Hollows FC, Graham P A. Intra-ocular pressure, glaucoma, and glaucoma suspects in a defined population. Br J Ophthalmol 1966;50:570-86. 3. Tielsch JM, Sommer A, Katz J, et al. Racial variations in the prevalence of primary open-angle glaucoma. The Baltimore Eye Survey. JAMA 1991;266:369-74. 4. Viggosson G, Bjornsson G, Ingvason JG. The prevalence of open angle glaucoma in Iceland. Acta Ophthalmol (Copenh) 1986;64:138-41.

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Age (yrs) 2: 2: 2: 2:

55 55 40 40

Proportion of Eyes (%) 3.8 47.8 61.1 37.0

5. Oh YG, Minelli S, Spaeth GL, Steinman WC. The anterior chamber angle is different in different racial groups: a gonioscopic study. Eye 1994;8:104-8. 6. Alsbirk PH. Early detection of primary angle-closure glaucoma: Iimbal and axial chamber depth screening in a high risk population (Greenland Eskimos). Acta Ophthalmol (Copenh) 1988;66:556-64. 7. Alsbirk PH. Primary angle-closure glaucoma. Oculometry, epidemiology, and genetics in a high risk population. Acta Ophthalmol Suppl 1976; 127:5-31. 8. Arkell SM, Lightman DA, Sommer A, et al. The prevalence of glaucoma among Eskimos of northwest Alaska. Arch Ophthalmol 1987; 105:482-5. 9. Clemmesen V, Alsbirk PH. Primary angle-closure (a.c.g.) glaucoma in Greenland. Acta Ophthalmol (Copenh) 1971;49:47-58. 10. Cox JE. Angle-closure glaucoma among the Alaskan Eskimo. Glaucoma 1984;6:135-7. 11. Drance SM. Angle closure among Canadian Eskimos. Can J Ophthalmol 1973;8:252-4. 12. Van Rens GHMB, Arkell SM, Charlton W, Doesburg W. Primary angle-closure glaucoma among Alaskan Eskimos. Doc Ophthalmol 1988;70:265-76. 13. Congdon N, Wang F, Tielsch JM. Issues in the epidemiology and population-based screening of primary angle-closure glaucoma. Surv Ophthalmol 1992;36:411-23. 14. Pararajasegaram R. Glaucoma pattern in Ceylon. Trans Asia Pac Acad Ophthalmol 1968;3:274-8. 15. Linner E. Assessment of glaucoma as a cause of blindness, India. World Health Organization SE Asia Region/Ophthalmol 1982; 55(2). 16. Kitazawa Y. Epidemiology of primary angle-closure glaucoma. Asia-Pac J Ophthalmol 1990;2:78-81. 17. Shiose Y, Kitazawa Y, Tsukahara S, et al. Epidemiology of glaucoma in Japan-a nationwide glaucoma survey. Jpn J Ophthalmol 1991;35:133-55. 18. Hu CN. An epidemiologic study of glaucoma in Shunyi County [In Chinese]. Chung Hua Yen Ko Tsa Chih 1989;25:115-9. 19. Drance SM, Morgan RW, Bryett J, Fairclough M. Anterior chamber depth and gonioscopic findings among the Eskimos and Indians in the Canadian arctic. Can J Ophthalmol 1973;8:255-9. 20. Alsbirk PH, Forsius H. Anterior chamber depth in Eskimos from Greenland, Canada (Igloolik) and Alaska (Wainwright): a preliminary report. Can J Ophthalmol 1973; 8:265-9. 21. Zhao JL, Hu Z. The clinical examination of anterior chamber depth in eyes with primary angle-closure glaucoma [in Chinese]. Eye Science 1989;6:1-5. 22. Luntz MH. Primary angle-closure glaucoma in urbanized

Nguyen et al . Occludable Angles in a Vietnamese Population

23. 24. 25. 26. 27. 28.

South African caucasoid and negroid communities. Br J Ophthalmol 1973;57 :445 -56. Tornquist R. Shallow anterior chamber in acute glaucoma; A Clinical and Genetic Study. Acta Ophthalmol (Copenh) 1953; Supp 39: 1-74. Lowe RF. Primary angle closure glaucoma: a review of provocative testing. Br J Ophthalmol 1967;51:727-32. Lowe RF. Acute angIe closure glaucoma. The second eye: an analysis of 200 cases. Br J OphthaImoI1962;46:641-50. Winter Fe. The second eye in acute, primary, shallow-chamber angle glaucoma. Am J OphthaImol 1955;40:557-8. Panek WC, Christensen RE, Lee DA, et al. Biometric variables in patients with occludable anterior chamber angles. Am J Ophthalmol 1990; 110: 185-8. Wilensky IT, Kaufman PL, Frohlichstein D, et al. Followup of angle-closure glaucoma suspects. Am J Ophthalmol 1993; 115:338-46.

29 . Alward WLM. Color Atlas of Gonioscopy. London : Wolfe, 1994;52. 30. Leighton DA, Phillips CI, Tsukahara S. Profile of presenting status of eyes in angle closure glaucoma. Br J Ophthalmol 1971;55:577-84. 31. Hyams SW, Friedman Z, Keroub C. Fellow eye in angle closure glaucoma. Br J Ophthalmol 1975;59:207-10. 32. Lowe RF. Clinical types of primary angle closure glaucoma. Aust N Z J Ophthalmol 1988; 16:245-50. 33. Lim ASM. Primary angle-closure glaucoma in Singapore. Aust J Ophthalmol 1979;7:23-30. 34. Quigley HA. Long-term follow-up of laser iridotomy. Ophthalmology 1981 ;88:2 18-24. 35. Schwartz AL, Weiss HS. Laser surgery in glaucoma. In: Tasman W, Jaeger EA, eds. Duane's Clinical Ophthalmology, rev. ed. Vol. 6. Philadelphia: Lippincott-Raven Publishers, 1995;chap. 19.

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* Centennial advertisement provided courtesy of the Museum of Ophthalmology, Foundation of the American Academy of Ophthalmology, San Francisco, California

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