- Email: [email protected]
Contact Lenses and Corneal Curvature Changes*
852
S. P. A M 0 1 L S
instru-
an exhaust port. The gas passages are housed in a standard ballpoint pen (fig. 2 ) . The nylon tube is connected to a carbon-dioxide cylinder via a needle valve and pressure gauge and an electric solenoid valve operated by means of a foot switch. By varying the gas pressure using the fine adjustment needle-valve, the temperature can be varied from ambient to — 75°C. Immediately the solenoid valve is closed and the gas supply interrupted, the probe temperature rises. This rise is extremely rapid due to the low thermal capacity of the probe tip and immediate cooling occurs once the gas flow is restarted. Approximately 100 cataract extractions can be performed, using a 3-lb cylinder of carbon dioxide. The cost of the probe and control equipment is very low. A paper describing 40 cases in which this instrument has been used is in preparation.
tained in an outer casing constructed from an 18gauge needle closed at one end with a plate of stainless steel and silver soldered to a hollow copper ballpoint refill. The inner gas passage is connected to a flexible nylon tube one-eighth inch in diameter. The outer gas passage is connected to
I wish to thank Prof. Maurice Luntz for his invaluable guidance and suggestions and to thank Dr. W. H . F. Kenny, superintendent of Baragwanath Hospital, for permission to publish these case reports.
Fig. 2 (Atnoils). Improved cryosurgical ment.
ACKNOWLEDGMENTS
REFERENCES 1. Krwawicz, T. : Intracapsular extraction of intumescent lenses by application of low temperature. Brit. Î. Ophth., 45:279-283, 1961. 2. Kellman, C. D., and Cooper, I. S. : Cryogenic ophthalmic surgery. Am. J. Ophth., 56 :731-738, 1963. 3. Bellows, J. G. : The application of cryogenic tecniques in ophthalmology. Am. J. Ophth., 57 :29-33, 1964.
CONTACT LENSES AND CORNEAL CURVATURE CHANGES* JOHN A. PRATT-JOHNSON, F.R.C.S., AND DAVID M. WARNER, Vancouver, Canada
Changes in the physical contour of the cornea with contact-lens wear have been recognized by several authors.3 "3 These changes can be divided into two major groups: (1) molding, defined as a passive change in the physical contour of the cornea associated with contact lens wear and (2) corneal edema manifested clinically by a corneal haze seen best by sclerotic scatter and retroillumination using the slitlamp biomicroscope. Either of these changes can * From the Department of Ophthalmology, Faculty of Medicine, University of British Columbia.
M.B.
produce the phenomenon known as spectacle blur. Spectacle blur is a transient alteration in the visual acuity on resuming spectacles after contact-lens wear. This report analyzes the frequency of edema and molding in a series of 200 eyes fitted with corneal contact lenses. METHODS
Corneal contact lenses were fitted according to the following principles : The base curve corresponded to the keratometric reading of the flattest meridian. However, some of the lenses were fitted a
CORNEAL CURVATURE CHANGES
quarter of a diopter flatter than this reading. The diameter of the lens was determined arbitrarily and varied between 8.2 and 10.5 mm, the majority being 9.0 to 9.4 mm. One peripheral curve 0.4 mm in width, and 12.25 mm in radius was used in most cases. Patients with corneal astigmatism of over 2.5D have been excluded from this series because these patients were fitted with lenses having a toric base-curve. The wearing time was increased to four hours continuous wear over the course of week. At this stage, the patient returned wearing the lens which has been inserted four hours previously. Keratometry and slitlamp microscopy were repeated after removal of the lenses. No patient in this series had any modification of the contact lenses until after this four-hour assessment. RESULTS
For the purposes of this study, a significant change in the corneal curvature was taken to be a change in either direction of half a diopter or more. Table 1 shows the total number of cases showing a significant change in the corneal curvature or edema after four hours of contact lens wear. In order to study the relationship between the corneal astigmatism and the amount of molding at four hours, the cases have been divided into two groups : Group A in which the amount of corneal astigmatism originally present was more than half a diopter. Group B in which the amount of corneal astigmatism was less than half a diopter. In Table 2, it is to be noted that 73.5% of TABLE 1 CORNEAL CHANGES AFTER FOUR HOURS CONTACT LENS WEAR
(200 eyes)
Eyes with insignificant changes in the corneal curvature (less than 0.5 D) Eyes with significant changes in the corneal curvature (more than 0.5D) Eyes with clinically detectable edema
55 145 9
853 TABLE 2
ANALYSIS OF ORIGINAL CORNEAL ASTIGMATISM
A. Total number of cases with initial astigmatism of more than half diopter
147
73.5%
B. Number of cases with initial astigmatism of less than half diopter
53
26.5%
TOTAL CASES
200
100%
the eyes had over half a diopter of corneal astigmatism present before fitting. Table 3 shows the comparison of the effect of original corneal astigmatism on the resultant molding. It is interesting to note that more than half of the cases in either group showed significant molding. It is also noteworthy that a higher precentage of molding occurred in the cases in Group A. In Table 4, the principal meridians of Group A are analyzed and studied. It can be seen that, when molding occurred, it was in the direction of steepening in 97% of cases. The flattest meridian was most commonly affected. DISCUSSION
The results show that significant changes in the corneal curvature are commonly associated with contact-lens wear. It has been observed that the amount of molding increases progressively with increasing lens wearing time. No analysis of this tendency has been included in this paper because in a large percentage of cases the lenses had been modified after the four-hour examination. These modifications have included reduction in the lens size, increase in the width of the peripheral curve or the addition of secondary curves. Girard, et al4 infer that most changes in corneal curvature are due to edema but this has not been demonstrated in this study which has been limited to four hours of contact-lens wear. Corneal edema seen by sclerotic scatter or retroillumination was more commonly seen after long periods of wear, particularly if the wearing time was increased too rapidly.
J O H N A. P R A T T - J O H N S O N A N D D A V I D M. W A R N E R
854
TABLE 3 T H E EFFECT OF ORIGINAL CORNEAL ASTIGMATISM ON RESULTANT CORNEAL MOLDING
Change in Either Meridian of More than Half a Diopter A. More than half a diopter astigmatism initially
147
114
B. Less than half a diopter astigmatism initially
S3
31
200
145
PRACTICAL IMPLICATIONS OF MOLDING 1. FLUORESCEIN PATTERN
The fluorescein pattern has been the standard method used by many to evaluate contact-lens fit. In our opinion, this method is open to serious criticism because the majority of eyes show a change in the corneal curvature after even short periods of contact lens wear (four hours). Apical touch at the onset of contact-lens wear means that the lens is too flat, whereas too tight a lens after molding may give an identical appearance. Photophobia, common in the adaptive phase of contact-lens wear and accentuated by the examining light, results in excessive tearing and further distortion of the fluorescein pattern. For these two reasons, the fluorescein pattern is of value principally in
Molding of Less than Half a Diopter %
78%
33
22%
57.0%
22
43.0%
55
estimating the original fit of the lens, but only if topical anesthesia is used to reduce tearing. 2. CLINICAL IMPLICATIONS
It is important, clinically, in evaluating the fit of a contact lens fitted elsewhere that the original keratometric reading is available for comparison with the keratometric reading obtained during the examination after contact lens wear. A comparison of these two readings enables an estimation of the molding to be made. The satisfactory prescription of glasses for the contact-lens wearer necessitates knowledge of the amount of molding present while the contact lenses are being worn and the persistence of this molding after they are removed.
TABLE 4
SUMMARY
ANALYSIS OF CHANGES IN THE PRINCIPAL MERIDIANS IN GROUP A AFTER FOUR-HOUR WEAR
This report analyzes the frequency of corneal molding in 200 eyes after four hours of corneal contact-lens wear. The commonest change was an increase in the corneal curvature. Changes occurred more frequently in those eyes with an original corneal astigmatism of more than half a diopter. Clinically detectable edema at this four-hour stage was rare. Criticism is levelled at the reliance upon the fluorescein pattern as a method of contact-lens fitting. It is suggested that thorough knowledge of the molding gathered from repeated keratometric readings is mandatory in evaluating the fit of a contact lens. 2550 Willow Street (9).
(Total Cases 147)
Steeper by Half Diopter or More Changes in the meridian
flatter
Changes in the steeper meridian Changes in both meridians of more than half a diopter Changes in either meridian of more than half a diopter
94
+
68
+
Flatter by More than Half Diopter 0
=94 74
54
= 114
CORNEAL CURVATURE CHANGES
855
REFERENCES
1. Raiford, M. B. : Contact Lens Management Boston, Little, 1961, p. 69. 2. Girard, L. J., Soper, J. W., and Sampson, W. G. : Corneal Contact Lenses. St. Louis, Mosby, 1964, p. 245. 3. Dixon, J. M. : Pathology of the eye due to contact lens wear. Tr. Pacif. Coast Oto-Ophth. Soc, 44:103-121, 1963. 4. Girard, L. J., Soper, J. W., and Sampson, W. G. : Corneal Contact Lenses. St. Louis, Mosby, 1964, p. 267.
COATS' DISEASE* N A T U R A L HISTORY A N D RESULTS OF T R E A T M E N T ADOLFO G O M E Z M O R A L E S ,
M.D.
Buenos Aires, Argentina Numerous articles dealing with Coats' disease published since the original description 1 indicate the confusion regarding the nature and diagnostic criteria of this ocular disorder. Furthermore, once the diagnosis has been made, little is known regarding treatment, and three questions are likely to arise: ( a ) W h a t is the natural history of the ocular disturbance? ( b ) W h a t are the indications for therapy, if any? (c) W h a t has been the result in those few cases in which therapeutic efforts have been made? In the present study, the histories of 51 patients with the diagnosis of Coats' disease were reviewed with special reference to the natural history of this disease. T h e diagnostic criteria employed for inclusion in this study were those originally described by Coats himself. I n addition, the results in a small group of those patients who were treated with diathermy and photocoagulation will be evaluated. H I S T O R I C A L NOTE
A complete review of the literature dealing with Coats' disease may be found in the recent publications of Fregnan, 2 Imre, 3 * From the Tumor Clinic (Director: A. B. Reese, M.D.), Institute of Ophthalmology, Columbia-Presbyterian Medical Center, New York. This work was supported by a fellowship award from the Pan-American Association of Ophthalmology.
Woods and Duke. 4 ' 5 In his original report Coats described three varieties of the disease. Clinical diagnosis in the present series was based upon the characteristics assigned by Coats to his varieties No. 1 and No. 2. Variety No. 3 has since been recognized as an independent entity (von Hippel-Lindau disease). I n his original contribution, Coats listed the clinical characteristics of varieties No. 1 and No. 2 as follows : 1. Presence in the fundus of large masses of white or yellow exudation. 2. Usually there are also groups of cholesterin crystals and hemorrhage. 3. In an allied form of the disease, or in a variety of the same form, strange types of vascular disease are found: fusiform and globular expansions, kinks, loops, glomeruli, etc. 4. In some instances, the eye is eventually lost from detachment of the retina, secondary cataract, iritis or secondary glaucoma. 5. The affection occurs in young people, most commonly of the male sex. 6. No definite connection with former illnesses can be established. M a n y authors have expressed the opinion that Coats' disease is a form of retinal angiomatosis. 6 ~ 20 Reese 1 5 has previously reviewed some of the cases at this hospital and has expressed the opinion that the basic pathologic process is a thickening of the basement membrane of the retinal vascular channels progressing to telangiectasis ; Leber's disease 21 is a forerunner of Coats' disease, in his opinion.
S. P. A M 0 1 L S
instru-
an exhaust port. The gas passages are housed in a standard ballpoint pen (fig. 2 ) . The nylon tube is connected to a carbon-dioxide cylinder via a needle valve and pressure gauge and an electric solenoid valve operated by means of a foot switch. By varying the gas pressure using the fine adjustment needle-valve, the temperature can be varied from ambient to — 75°C. Immediately the solenoid valve is closed and the gas supply interrupted, the probe temperature rises. This rise is extremely rapid due to the low thermal capacity of the probe tip and immediate cooling occurs once the gas flow is restarted. Approximately 100 cataract extractions can be performed, using a 3-lb cylinder of carbon dioxide. The cost of the probe and control equipment is very low. A paper describing 40 cases in which this instrument has been used is in preparation.
tained in an outer casing constructed from an 18gauge needle closed at one end with a plate of stainless steel and silver soldered to a hollow copper ballpoint refill. The inner gas passage is connected to a flexible nylon tube one-eighth inch in diameter. The outer gas passage is connected to
I wish to thank Prof. Maurice Luntz for his invaluable guidance and suggestions and to thank Dr. W. H . F. Kenny, superintendent of Baragwanath Hospital, for permission to publish these case reports.
Fig. 2 (Atnoils). Improved cryosurgical ment.
ACKNOWLEDGMENTS
REFERENCES 1. Krwawicz, T. : Intracapsular extraction of intumescent lenses by application of low temperature. Brit. Î. Ophth., 45:279-283, 1961. 2. Kellman, C. D., and Cooper, I. S. : Cryogenic ophthalmic surgery. Am. J. Ophth., 56 :731-738, 1963. 3. Bellows, J. G. : The application of cryogenic tecniques in ophthalmology. Am. J. Ophth., 57 :29-33, 1964.
CONTACT LENSES AND CORNEAL CURVATURE CHANGES* JOHN A. PRATT-JOHNSON, F.R.C.S., AND DAVID M. WARNER, Vancouver, Canada
Changes in the physical contour of the cornea with contact-lens wear have been recognized by several authors.3 "3 These changes can be divided into two major groups: (1) molding, defined as a passive change in the physical contour of the cornea associated with contact lens wear and (2) corneal edema manifested clinically by a corneal haze seen best by sclerotic scatter and retroillumination using the slitlamp biomicroscope. Either of these changes can * From the Department of Ophthalmology, Faculty of Medicine, University of British Columbia.
M.B.
produce the phenomenon known as spectacle blur. Spectacle blur is a transient alteration in the visual acuity on resuming spectacles after contact-lens wear. This report analyzes the frequency of edema and molding in a series of 200 eyes fitted with corneal contact lenses. METHODS
Corneal contact lenses were fitted according to the following principles : The base curve corresponded to the keratometric reading of the flattest meridian. However, some of the lenses were fitted a
CORNEAL CURVATURE CHANGES
quarter of a diopter flatter than this reading. The diameter of the lens was determined arbitrarily and varied between 8.2 and 10.5 mm, the majority being 9.0 to 9.4 mm. One peripheral curve 0.4 mm in width, and 12.25 mm in radius was used in most cases. Patients with corneal astigmatism of over 2.5D have been excluded from this series because these patients were fitted with lenses having a toric base-curve. The wearing time was increased to four hours continuous wear over the course of week. At this stage, the patient returned wearing the lens which has been inserted four hours previously. Keratometry and slitlamp microscopy were repeated after removal of the lenses. No patient in this series had any modification of the contact lenses until after this four-hour assessment. RESULTS
For the purposes of this study, a significant change in the corneal curvature was taken to be a change in either direction of half a diopter or more. Table 1 shows the total number of cases showing a significant change in the corneal curvature or edema after four hours of contact lens wear. In order to study the relationship between the corneal astigmatism and the amount of molding at four hours, the cases have been divided into two groups : Group A in which the amount of corneal astigmatism originally present was more than half a diopter. Group B in which the amount of corneal astigmatism was less than half a diopter. In Table 2, it is to be noted that 73.5% of TABLE 1 CORNEAL CHANGES AFTER FOUR HOURS CONTACT LENS WEAR
(200 eyes)
Eyes with insignificant changes in the corneal curvature (less than 0.5 D) Eyes with significant changes in the corneal curvature (more than 0.5D) Eyes with clinically detectable edema
55 145 9
853 TABLE 2
ANALYSIS OF ORIGINAL CORNEAL ASTIGMATISM
A. Total number of cases with initial astigmatism of more than half diopter
147
73.5%
B. Number of cases with initial astigmatism of less than half diopter
53
26.5%
TOTAL CASES
200
100%
the eyes had over half a diopter of corneal astigmatism present before fitting. Table 3 shows the comparison of the effect of original corneal astigmatism on the resultant molding. It is interesting to note that more than half of the cases in either group showed significant molding. It is also noteworthy that a higher precentage of molding occurred in the cases in Group A. In Table 4, the principal meridians of Group A are analyzed and studied. It can be seen that, when molding occurred, it was in the direction of steepening in 97% of cases. The flattest meridian was most commonly affected. DISCUSSION
The results show that significant changes in the corneal curvature are commonly associated with contact-lens wear. It has been observed that the amount of molding increases progressively with increasing lens wearing time. No analysis of this tendency has been included in this paper because in a large percentage of cases the lenses had been modified after the four-hour examination. These modifications have included reduction in the lens size, increase in the width of the peripheral curve or the addition of secondary curves. Girard, et al4 infer that most changes in corneal curvature are due to edema but this has not been demonstrated in this study which has been limited to four hours of contact-lens wear. Corneal edema seen by sclerotic scatter or retroillumination was more commonly seen after long periods of wear, particularly if the wearing time was increased too rapidly.
J O H N A. P R A T T - J O H N S O N A N D D A V I D M. W A R N E R
854
TABLE 3 T H E EFFECT OF ORIGINAL CORNEAL ASTIGMATISM ON RESULTANT CORNEAL MOLDING
Change in Either Meridian of More than Half a Diopter A. More than half a diopter astigmatism initially
147
114
B. Less than half a diopter astigmatism initially
S3
31
200
145
PRACTICAL IMPLICATIONS OF MOLDING 1. FLUORESCEIN PATTERN
The fluorescein pattern has been the standard method used by many to evaluate contact-lens fit. In our opinion, this method is open to serious criticism because the majority of eyes show a change in the corneal curvature after even short periods of contact lens wear (four hours). Apical touch at the onset of contact-lens wear means that the lens is too flat, whereas too tight a lens after molding may give an identical appearance. Photophobia, common in the adaptive phase of contact-lens wear and accentuated by the examining light, results in excessive tearing and further distortion of the fluorescein pattern. For these two reasons, the fluorescein pattern is of value principally in
Molding of Less than Half a Diopter %
78%
33
22%
57.0%
22
43.0%
55
estimating the original fit of the lens, but only if topical anesthesia is used to reduce tearing. 2. CLINICAL IMPLICATIONS
It is important, clinically, in evaluating the fit of a contact lens fitted elsewhere that the original keratometric reading is available for comparison with the keratometric reading obtained during the examination after contact lens wear. A comparison of these two readings enables an estimation of the molding to be made. The satisfactory prescription of glasses for the contact-lens wearer necessitates knowledge of the amount of molding present while the contact lenses are being worn and the persistence of this molding after they are removed.
TABLE 4
SUMMARY
ANALYSIS OF CHANGES IN THE PRINCIPAL MERIDIANS IN GROUP A AFTER FOUR-HOUR WEAR
This report analyzes the frequency of corneal molding in 200 eyes after four hours of corneal contact-lens wear. The commonest change was an increase in the corneal curvature. Changes occurred more frequently in those eyes with an original corneal astigmatism of more than half a diopter. Clinically detectable edema at this four-hour stage was rare. Criticism is levelled at the reliance upon the fluorescein pattern as a method of contact-lens fitting. It is suggested that thorough knowledge of the molding gathered from repeated keratometric readings is mandatory in evaluating the fit of a contact lens. 2550 Willow Street (9).
(Total Cases 147)
Steeper by Half Diopter or More Changes in the meridian
flatter
Changes in the steeper meridian Changes in both meridians of more than half a diopter Changes in either meridian of more than half a diopter
94
+
68
+
Flatter by More than Half Diopter 0
=94 74
54
= 114
CORNEAL CURVATURE CHANGES
855
REFERENCES
1. Raiford, M. B. : Contact Lens Management Boston, Little, 1961, p. 69. 2. Girard, L. J., Soper, J. W., and Sampson, W. G. : Corneal Contact Lenses. St. Louis, Mosby, 1964, p. 245. 3. Dixon, J. M. : Pathology of the eye due to contact lens wear. Tr. Pacif. Coast Oto-Ophth. Soc, 44:103-121, 1963. 4. Girard, L. J., Soper, J. W., and Sampson, W. G. : Corneal Contact Lenses. St. Louis, Mosby, 1964, p. 267.
COATS' DISEASE* N A T U R A L HISTORY A N D RESULTS OF T R E A T M E N T ADOLFO G O M E Z M O R A L E S ,
M.D.
Buenos Aires, Argentina Numerous articles dealing with Coats' disease published since the original description 1 indicate the confusion regarding the nature and diagnostic criteria of this ocular disorder. Furthermore, once the diagnosis has been made, little is known regarding treatment, and three questions are likely to arise: ( a ) W h a t is the natural history of the ocular disturbance? ( b ) W h a t are the indications for therapy, if any? (c) W h a t has been the result in those few cases in which therapeutic efforts have been made? In the present study, the histories of 51 patients with the diagnosis of Coats' disease were reviewed with special reference to the natural history of this disease. T h e diagnostic criteria employed for inclusion in this study were those originally described by Coats himself. I n addition, the results in a small group of those patients who were treated with diathermy and photocoagulation will be evaluated. H I S T O R I C A L NOTE
A complete review of the literature dealing with Coats' disease may be found in the recent publications of Fregnan, 2 Imre, 3 * From the Tumor Clinic (Director: A. B. Reese, M.D.), Institute of Ophthalmology, Columbia-Presbyterian Medical Center, New York. This work was supported by a fellowship award from the Pan-American Association of Ophthalmology.
Woods and Duke. 4 ' 5 In his original report Coats described three varieties of the disease. Clinical diagnosis in the present series was based upon the characteristics assigned by Coats to his varieties No. 1 and No. 2. Variety No. 3 has since been recognized as an independent entity (von Hippel-Lindau disease). I n his original contribution, Coats listed the clinical characteristics of varieties No. 1 and No. 2 as follows : 1. Presence in the fundus of large masses of white or yellow exudation. 2. Usually there are also groups of cholesterin crystals and hemorrhage. 3. In an allied form of the disease, or in a variety of the same form, strange types of vascular disease are found: fusiform and globular expansions, kinks, loops, glomeruli, etc. 4. In some instances, the eye is eventually lost from detachment of the retina, secondary cataract, iritis or secondary glaucoma. 5. The affection occurs in young people, most commonly of the male sex. 6. No definite connection with former illnesses can be established. M a n y authors have expressed the opinion that Coats' disease is a form of retinal angiomatosis. 6 ~ 20 Reese 1 5 has previously reviewed some of the cases at this hospital and has expressed the opinion that the basic pathologic process is a thickening of the basement membrane of the retinal vascular channels progressing to telangiectasis ; Leber's disease 21 is a forerunner of Coats' disease, in his opinion.