- Email: [email protected]
Keratoconus
I(eratoconU5 Contact Lens or I(eratopiasty? WILLIAM E. SMIDDY, MD, TRACEY R. HAMBURG, COT, GREGORY P. KRACHER, OD, WALTER J. STARK, MD
Abstract: The success rate of contact lens fitting and rate of progression to keratoplasty were evaluated for 115 consecutive patients with keratoconus. Of 190 nonoperated eyes that needed to be fit, 25 (13%) could not be fit, whereas 165 eyes (87%) could be fit. Most of these eyes had been referred for keratoplasty after previous contact lens fittings had no longer been successful. Of the 165 eyes that could be fit, 51 (31 %) ultimately needed keratoplasty after an average of 38.4 months of lens wear, and 114 eyes (69%) did not require keratoplasty over an average follow-up interval of 63 months of wearing contact lenses. The average initial keratoplasty reading in these two groups was 56.8 and 51.8 diopters (D), respectively. Special design, bispheric lenses were required in 125 of these 165 eyes (76%) and frequent lens changes were necessary. Of 88 postoperative eyes, 53 (60%) wore contact lenses for best vision. Keratoplasty can be delayed or avoided in many keratoconus patients by using contact lenses, especially special design, bispheric lenses. Also, keratoconus eyes often need contact lenses after keratoplasty. [Key words: bispheric (Soper-cone) lens, contact lens, keratoconus, penetrating keratoplasty.] Ophthalmology 95:487-492, 1988
Keratoconus is an ectatic corneal disorder characterized by central thinning and protrusion of the central cornea. It is idiopathic in nature and frequently leads to decreased vision. A majority of patients may be visually corrected using spectacles or contact lens fitting. However, epidemiologic studies have shown that 10 to 20% of patients will ultimately require penetrating keratoplasty.l,2 The purpose of this study is (1) to determine the proportion of patients with keratoconus fitted successfully with contact lenses, (2) to determine the proportion of patients who require keratoplasty, (3) to characterize the types and numbers oflenses that are needed to achieve a satisfactory, nonsurgical visual result, and (4) to assess the visual outcome in those undergoing surgery. Originally received: October 19, 1987. Revision accepted: December 29, 1987. From the Contact Lens Service and the Comeal Service, The Wilmer Institute, The Johns Hopkins Medical Institutions, Baltimore. Presented in part at the American Academy of Ophthalmology Annual Meeting, Dallas, November 1987. Reprint requests to Walter J. Stark, MD, Maumenee 327, The Johns Hopkins Hospital, 600 N. Wolfe St, Baltimore, MD 21205.
PATIENTS AND METHODS We reviewed the charts of230 eyes of 115 consecutive patients who reported as new patients to the Cornea Service of the Wilmer Eye Institute from 1977 to 1982 for consideration of penetrating keratoplasty. Inclusion of new patients into this study was truncated at this point, but patients were followed through May 1987 allowing for an adequate follow-up interval for most eyes. Patients were excluded from the study if they presented one time only for evaluation and if the contact lens fitting was not managed by our service. Historic features that were recorded on admission included (1) age, (2) sex, (3) duration of diagnosis of keratoconus, (4) previous experience with contact lens fitting, and (5) the status of the fellow eye. A complete ocular examination was provided, including a manifest refraction, keratometry readings, slit-lamp examination, and dilated fundus examination. For purposes of data analysis, eyes were not averaged in if the mires were too distorted to enable keratometry reading, thus probably underestimating the true average keratometry readings. Many times the recorded reading was the upper limit of the keratometer scale and the actual keratometric reading was probably 487
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higher. In these eyes, the upper limit of the keratometer was used for data analysis, again underestimating the true average keratometry readings. If the patient's visual acuity was not satisfactory with a spectacle correction, an attempt was first made to fit the patient with a spherical hard contact lens. Initially, polymethylmethacrylate (PMMA) lenses were used, but more recently gas-permeable lenses have been used for this purpose. If a hard or gas-permeable spherical lens was not satisfactorily tolerated, a fitting using a soft contact lens was attempted in selected patients. When patients could not tolerate the hard contact lens and were unable to achieve satisfactory vision with soft contact, then a fitting was attempted with a special design, bispheric lens. We used the Soper-cone variety of bispheric contact lenses. Scleral-fitted contact lenses were not used in this study, and successful results with combination lenses and "piggyback" systems were limited during this period. Whenever possible, keratometry readings are obtained and trial lenses are chosen equal to the flattest reading. A best-fit contact lens demonstrates no evidence of air beneath the lens peripherally or centrally so that there is an equal distribution of fluorescein to all corresponding weightbearing areas of the cornea. This may be referred to as three-point touch and to insure the proportion of bearing (touch) to fluorescein is approximately 50% of the total pattern. Careful attention to the doughnut ring width is made to avoid a narrow ring which will diminish tear exchange. It also has been our impression that the Soper lenses work best with corneas steeper than 50 diopters (D). The optimum fit is determined with final variances in diameter to allow stability of the vision and centration of the contact lens. A successful fit was defined as adequate vision and daily contact lens wear for at least 6 months. Eyes that could not be fitted were scheduled for penetrating keratoplasty. Experience with epikeratophakia during this time interval was limited, and epikeratophakia was not performed in this group. The reasons for keratoplasty during our study included poor vision due to central corneal scarring despite a good fit and markedly decreased wearing time due to the inability to continue to maintain a comfortable fit. The reasons for penetrating keratoplasty in the 12 eyes that had undergone surgery before presenting to our service could not be determined. The time from our initial fit to keratoplasty was recorded for the patients who became contact lens-intolerant during the study period. Patients usually presented to our service already carrying the diagnosis of keratoconus, thus the duration from diagnosis to presentation to our service was not accurately quantifiable for many patients. Other data included the types and number of lenses that were needed over the study interval. Often these patients required changes in contact lens parameters for best fit. Therefore, the number of lenses used in these patients was imprecise. For this reason, the range of how many lenses needed for each eye was tabulated and categorized as (1) one or two lenses, (2) three to ten lenses, 488
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and (3) over ten lenses. If a patient progressed from a hard spheric or soft lens to a special design, bispheric lens, the latter was recorded as the most recent lens used. In patients who either had undergone penetrating keratoplasty or subsequently underwent penetrating keratoplasty, postoperative visual acuity, and the method of visual rehabilitation was noted. Manifest refraction and keratometry readings were noted when possible. If contact lenses were used, the type of lenses and reasons for their use rather than spectacles were recorded.
RESULTS Two hundred thirty eyes of 115 consecutive patients were included in this study. The average age was 30.7 years (range, 11-75 years). There were 48 females and 67 males in the study group. The sex distribution and average age were similar for each subgroup analyzed including those who had previously undergone penetrating keratoplasty (31.0 years of age), those who underwent penetrating keratoplasty during follow-up in our study (31.2 years of age), and those who never underwent surgery (30.5 years of age). Upon initial presentation, 12 eyes had undergone previous keratoplasty, the current contact lens was adequate in 15 eyes, and spectacles provided adequate visual function for 13 eyes. The reason patients with lessadvanced keratoconus usually presented was to be fit for a contact lens in their fellow eye. There were 190 eyes that had not been operated on and had been considered to have failed previous contact lens fittings on presentation to our service. Almost all of these patients had been wearing contact lenses previously, but could no longer tolerate their current lens and/or could no longer be satisfactorily fit by their referring physician. At the initial fitting, 165 ofthese eyes (87%) could be successfully fit with a contact lens. Accordingly, a contact lens could not be successfully fit in 25 eyes (13%), and these patients were scheduled for keratoplasty. The keratometry reading was usually not measurable in this group, and when it could be measured was usually greater than 60 D (Table 1). During the follow-up interval, 51 of these 165 eyes (31%) became intolerant of contact lenses despite changing to new lenses, and were subsequently referred for keratoplasty. We termed these patients the prekeratoplasty group, even though this was a retrospective assignment. However, 114 of the 165 eyes (69%) did not require keratoplasty over the follow-up interval, which ranged from 6 to 125 months (average, 62.7 months; median, 60 months). These patients formed our nonkeratoplasty group. NONKERATOPLASTY GROUP
There were 114 eyes that did not require keratoplasty during an average follow-up interval of 62.7 months (Table 2). Of these eyes, 58 (51 %) required one or two different lenses, 52 (46%) required three to ten different
SMIDDY et al
lenses, and four (4%) required more than ten different lenses during the follow-up period (Table 3). The special design, bispheric lens was necessary in 82 of these 114 eyes (72%), whereas spherical (PMMA or gas-permeable) lenses were fit for 32 eyes (28%) (Table 4). Soft contact lenses were not the final lens for any patient although three patients in the study derived enough benefit that they wore them at some point during the study interval. In the few patients who used them, they either were not visually successful or a subsequent special design, bispheric lens was fit. The visual acuity was 20/40 or better with the contact lenses in 88 of these 114 eyes (77%),20/50 to 20/100 in 23 eyes (20%), and 20/200 or worse (due to a previous retinal detachment, amblyopia, and optic neuropathy) in 3 eyes (3%). The visual acuity while wearing contact lenses was 20/20 to 20/40 in 88 of the 114 nonkeratoplasty eyes (77%),20/50 to 20/100 in 23 eyes (20%), and 20/200 or worse in 3 eyes (3%). Keratometry readings were taken at initial presentation in all patients and are summarized in Table 1. For the nonkeratoplasty group, the average reading was 51.8 D. The average initial keratometry reading was at least 50.0 in over one half of these patients.
PREKERATOPLASTYGROUP Of the 165 eyes that were initially successful in the contact lens fitting, 51 required keratoplasty (31 %) an average of 38.4 months (median, 36 months) after the initial fitting (Table 2). This represents a 42% cumulative lO-year-risk of needing a penetrating keratoplasty after an initially successful contact lens fitting (Fig 1). It must be reiterated that this was a highly selected population, since most patients presented well after the initial diagnosis of keratoconus, typically after contact lens fittings elsewhere were no longer successful. Many of the patients needing keratoplasty had poor vision despite a good contact lens fitting and thus would be poor candidates for epikeratophakia. However, most keratoplasties were performed for inability to maintain a good-fitting contact lens. During the follow-up interval in this group of patients, one or two contact lenses were fit before the eye became intolerant of contact lenses in 17 eyes (33%), three to ten lenses were necessary in 27 eyes (53%), and more than ten contact lens changes were necessary in 7 eyes (14%) (Table 3). Before keratoplasty, the special design, bispheric variety lens was successfully fit in 43 of these eyes (84%), usually at presentation (Table 4). Eight of the 51 prekeratoplasty eyes (16%) either could not be fit at all or could not wear the lens for at least 6 months (our criterion for successful fit). Eyes in the nonkeratoplasty group usually required several lens changes, but not as many as in the prekeratoplasty group, as might be expected (Table 3). Similarly, special design, bispheric lenses were used frequently in the nonkeratoplasty group (72%), but were required more frequently in the prekeratoplasty group (84%) (Table 4).
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Table 1. Range and Average of Keratometric Readings Group (no. of eyes) CNF
Prekeratoplasty*
Nonkeratoplastyt
Average (0) Range (0) Too distorted 260 55-59 50-54 <50 Not available
59.2
56.8
51.8
7 6 2 0 1 9
3 22 7 9 9 1
0 21 20 19 52 2
Total eyes
25
51
114
CNF = could not fit on initial presentation; 0 = diopters. * Eyes that required keratoplasty during the study period. t Eyes that did not require keratoplasty during the study period.
Table 2. Follow-up and Results of 165 Patients with Initially Successful Contact Lens Fitting Follow-up Interval (mo)
Group
No. of Patients
(%)
Average
Range
Pre keratoplasty Nonkeratoplasty
51 114
(31) (69)
38.4' 62.7
6-125 6-125
Total
165
, Average interval to keratoplasty.
Table 3. Number of Lenses for Keratoconus Eyes No. of Eyes No. of Lenses
Nonkeratoplasty
Prekeratoplasty
(%)
Total (%)
58 (51) 52 (46) 4 (4)
17 (33) 27 (53) 7 (14)
75 (45) 79 (48) 11 (7)
(%)
<3 3-10 >10 Total
114
51
165
Postkeratoplasty
(%)
52 (98) 1 (2) 0(0) 53
Table 4. Types of Lenses for Keratoconus Eyes No. of Eyes Types of Lenses
Nonkeratoplasty
Pre keratoplasty
(%)
Total (%)
Bispheric Spherical hard
82 (72) 32 (28)
43 (84) 8 (16)
125 (76) 40 (24)
51
165
Total
(%)
114
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2
c:
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1.0 0.9 0.8 0.7
0
~
cu
c:
0.6
~ '0
0.5
E
UI
0.4
'0
0.3
.2
0.2
~ cu
-... c:
n=/65eyes
0
e Q.
0.1
0..
Months follow-up
Fig 1. Cumulative proportion of eyes maintained on contact lenses.
Table 5. Method of Visual Rehabilitation and the Reasons for Contact Lens Use in Eyes after Keratoplasty for Keratoconus Type of Visual Rehabilitation (no. of eyes) Reasons for Contact Lens Wear
Spectacles
Spherical Contact Lenses
Bispheric Contact Lenses
Total (%)
High astigmatism Anisometropia Irregular astigmatism Other
4 0
10 2
13 7
27
0 31
3 10
8 0
11 41
Total (%)
35 (40)
25 (28)
28 (32)
9
88 (100)
The average keratometry reading at initial presentation for this group was 56.8 D, and was at least 55 Din over one half of the eyes (Table 1).
POSTKERATOPLASTYGROUP A total of 88 eyes from this group had a keratoplasty at or after initial presentation. Twelve eyes had already had penetrating keratoplasty, 25 could not be fit initially and were scheduled for corneal transplantation, and 51 later required keratoplasty when they became intolerant to contact lens wear. The latter 76 eyes had surgery by one of us (WJS). Postoperative follow-up period averaged 54 months (range, 3-228 months) and lasted for at least 12 months in 81 of these 88 eyes. One patient had an episode of graft reaction during follow-up that cleared with treatment. 490
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Of these 88 eyes, 35 (40%) were visu~lly rehabilitated with spectacles. Contact lenses were fit in the remaining 53 eyes. Patients required postkeratoplasty contact lens fitting because of (1) postoperative astigmatism, (2) anisometropia from coexisting or induced myopia or aphakia, and (3) objectively or (4) subjectively improved vision over that obtained with spectacles (Table 5). Some patients in the third group probably achieved a better quality of vision due to neutralization of irregular, although low astigmatism. Many of those in the fourth group seemed primarily to be wearing the contact lenses out of convenience, since most patients wore contact lenses in the fellow eye and were experienced enough at wearing contact lenses to desire to wear them despite a marginal visual improvement. The postoperative astigmatism averaged 4.5 D, (range, 0-12 D), was 5.0 D or less in 61 of these 88 eyes (69%), and was more than 5.0 Din 27 eyes (31%). Four of the 27 eyes with high astigmatism have a visual acuity of at least 20/25 with about 5.0 D of cylinder in their spectacles. Two of these patients are 6 months postoperative and may eventually desire contact lenses with longer follow-up and after suture removal. These two patients wore contact lenses for 5 years before becoming intolerant of them and needed keratoplasty. All such eyes except these two have at least 1 year of follow-up after keratoplasty. The other 23 eyes were fit with contact lenses including special design, bispheric lenses in 13 eyes and spherical hard lenses in 10 eyes. Of the 61 postkeratoplasty eyes with 5.0 D or less of astigmatism, 30 wear contact lenses postoperatively including special design, bispheric lenses in 15 eyes and spherical hard lenses in 15. The reasons for contact lens use over spectacles in this group include anisometropia (preexisting or induced high myopia or aphakia) in 9 eyes, three or more Snellen lines better vision with contact lenses (due to neutralization of irregular astigmatism) in 11 eyes, and subjectively better vision in 10 other eyes. Eyes in the last group had 2.0 D or less of cylinder and an improvement of two Snellen lines with contact lenses. Nevertheless, the subjective visual improvement motivated these patients to wear contact lenses. This was probably easier for this group of patients since they were experienced contact lens wearers and usually had a greater visual benefit from the contact lens worn in the fellow eye. Indeed, 68 of the 88 fellow eyes (77%) of these patients were wearing contact lenses. The visual results were excellent. The corrected visual acuity was 20/20 or better in 48 of88 eyes (55%),20/25 to 20/40 in 31 eyes (35%), 20/50 to 20/200 in 8 eyes (9%), and limited to hand motions in 1 eye with optic neuropathy unrelated to surgery. The visual acuity with best manifest refraction was compared with the best visual acuity with contact lenses for the 53 patients who wore lenses after keratoplasty. This was not possible in seven eyes because of the inability to accurately refract these patients who typically had high or irregular astigmatism. In the 46 patients in whom a comparison was possible, there was an average 2.4 lines of improvement over spectacle correction with the contact lenses. The
SMIDDY et al
change in Snellen lines was zero in 13 eyes, one or two lines in 16 eyes, three or four lines in 9 eyes, and five or more lines in 8 eyes. Many patients had significant subjective improvements when the degree of astigmatism was higher, despite good visual acuity by manifest refraction.
DISCUSSION Most patients with keratoconus do not require penetrating keratoplasty, but 10 to 20% do come to keratoplasty.I,2 Contact lens fitting has improved the visual quality in many of these patients thereby delaying or preventing penetrating keratoplasty. Efforts at improving contact lens fitting techniques and materials could decrease the proportion of patients who requi~ surgical intervention. A variety of contact lens modalities have been used and developed to attain this goal. Many patients can be fit with rigid, non-gas-permeable spherical lenses, and their quality of vision frequently can be markedly improved. 3 A variety of scleral contact lenses also have been used with success rates of 85%.4,5 Semiflexible contact lenses,6 soft contact lenses,1-IO and a variety of more sophisticated contact lens fitting techniques such as the lens-lid attachment technique, II "piggyback" systems combining hard and soft lenses, 12 and the Saturn lens (combining soft and hard components in a single lens) have had limited success in our experience. More recently, a large number of patients have had success with gas-permeable rigid lens materials. 13-18 For patients with more marked astigmatism because of keratoconus and for those who have become intolerant to other contact lens modalities, the special design, bispheric contact lens (such as the Soper-cone lens)18 or aspheric lenses l9 are the only nonsurgical alternatives. It must be emphasized that this study population is a highly selected group and is not comparable with other published series of unselected patients. The degree of advanced keratoconus is evidenced by the distribution of keratometric readings in these eyes (Table 1). From this table, it is evident that of the 57 eyes with an initial keratometry reading between 50 and 60 D, 55 eyes (98%) were initially fit with a contact lens, and 39 eyes (68%) were maintained on contact lenses throughout the duration of the study. Most patients were referred when keratoplasty was being contemplated since contact lens fitting attempts were no longer successful. In an unselected population, contact lens fitting success rates would be expected to be higher. This study demonstrates that even a majority of these patients with advanced keratoconus can be successfully fit, and special design, bispheric lenses are frequently necessary. As might be expected, the degree of success correlated with the value of the keratometry reading, yet even the nonkeratoplasty group had fairly high keratometry readings. For many of these patients, this may require numerous follow-up visits with a large number of contact lens fittings over a long period of time. Although the costs of contact
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KERATOCONUS
lenses and repeated follow-up visits are not negligible, they compare favorably with those involved with even an uncomplicated surgical admission. More importantly, possible complications may be avoided. However, successful wear requires significant commitment on the part of the patients and the contact lens filter, but those undergoing keratoplasty require at least a similar degree of care and commitment. Initial results of epikeratophakia for keratoconus without corneal scarring have been encouraging,20 but penetrating keratoplasty remains the most common surgical alternative once contact lenses can no longer be fit. Further studies that clearly define equivalency of preoperative groups and at least equal postoperative results are needed before epikeratophakia becomes the treatment of choice. Most patients desire keratoplasty when they cannot be fit for contact lenses any longer or when the vision is not improved with the contact lenses because of corneal scarring. Some patients may expect that the surgical intervention will obviate the need for future contact lens wear, and may therefore desire surgery despite being able to be corrected successfully with a contact lens. Surgeons should caution patients with this misconception. In this study, 60% of eyes that underwent keratoplasty wear contact lenses postoperatively for best vision. In addition, many require a special design, bispheric lenses for best vision after keratoplasty. Refractive errors after keratoplasty remain a limiting factor in the success of penetrating keratoplasty,21,22 but contact lenses can be fit with a high degree of success after keratoplasty.9,23-27 Although astigmatism or anisometropia are the reason for contact lens use in about one half of these eyes, many patients wear the contact lenses for a subjective or marginal objective improvement in vision over spectacles. These patients are experienced with using contact lenses and usually wear a contact lens in their fellow eye. Many of those experiencing an objective improvement in vision probably benefit from neutralization by the rigid lens of irregular astigmatism. In a sizable proportion of eyes (28 of 53 eyes wearing lenses), special design, bispheric lenses provide the best fit and vision after keratoplasty. This may be because these lenses provide a larger peripheral flange to stabilize the contact lens on the host eye's peripheral corneal curvature. We prefer not to use larger than an 8.0 mm donor button to minimize the antigen load transplanted, thereby theoretically decreasing the risk of subsequent corneal graft rejection. The recipient bed is smaller by 0.25 or 0.50 mm depending on the presence of a crystalline lens. The most encouraging finding of this study is that most patients with keratoconus can maintain excellent vision with spectacles or contact lenses thereby avoiding surgery, despite the highly selected nature of these patients. With careful and persistent contact lens fitting and follow-up, keratoplasty can be delayed or avoided in many patients with keratoconus. This was the case in 69% of eyes in our highly selected patient group over a follow-up interval that averaged 5 years. This represents 491
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a 58% cumulative lO-year "survival" rate (Fig. 1). The rate of keratoplasty in an unselected group should be much lower. Keratoplasty should not be recommended when contact lenses can be effectively worn with good vision, since most patients will obtain their best postkeratoplasty vision with contact lenses. However, for patients who do require penetrating keratoplasty the surgical results for patients with keratoconus are very encouraging22,28 and in the 88 eyes that had penetrating keratoplasty in this study, the postoperative visual acuity was 20/40 or better in 90% of eyes.
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12. 13. 14. 15. 16. 17.
REFERENCES
18.
1. Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epiderniologic study of keratoconus. Am J Ophthalmol1986; 101:267-73. 2. Cohen EJ, Parlato CJ. Fitting polycon lenses in keratoconus. Int Ophthalmol Clin 1986; 26(1):111-7. 3. Carney LG. Contact lens correction of visual loss in keratoconus. Acta Ophthalmol 1982; 60:795-802. 4. Gould HL. Management of keratoconus with corneal and scleral lenses. Am J Ophthalmol1970; 70:624-9. 5. Hefny W, Rahim MH. Corneal contact lenses in management of keratoconus. Bull Ophthalmol Soc Egypt 1970; 63:291-3. 6. Gasset AR, Lobo L. Dura-T semiflexible lenses for keratoconus. Ann Ophthalmol1975; 7:1353-7. 7. Koliopoulos J, Tragakis M. Visual correction of keratoconus with soft contact lenses. Ann Ophthalmol1981; 13:835-7. 8. Lundh RL. Keratoconus: a disease that can be treated with soft lenses. Ophthalmologica 1978; 176:34-8. 9. Tragakis MP, Brown SI. Hydrophilic contact lenses for correcting irregular and high astigmatism. Arch Ophthalmol1972; 88:596-601. 10. Hull DS, Hyndiuk RA, Chin GN, Schultz RO. Clinical experience with the therapeutic hydrophilic contact lens. Ann Ophthalmol 1975; 7:555-62. 11. Mackie IA. Management of keratoconus with hard comeallenses: the
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27. 28.
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lens lid attachment technique. Trans Ophthalmol Soc UK 1977; 97:131-5. Buxton IN. Contact lenses in keratoconus. CLAO J 1978; 4(3):7485. Rosenthal P. The Boston Lens and the management of keratoconus. Int Ophthalmol Clin 1986; 26(1):101-9. Raber 1M. Fitting cellulose acetate butyrate lenses in keratoconus. Int Ophthalmol Clin 1986; 26(1):91-9. Maguen E, Espinosa G, Rosner IR, Nesburn AB. Long-term wear of Polycon contact lenses in keratoconus. CLAO J 1983; 9:57-9. Mobilia EF, Foster CS. A one-year trial of Polycon lenses in the correction of keratoconus. CLAO J 1979; 5(3):37-42. Raber 1M. Use of CAB Soper cone contact lenses in keratoconus. CLAO J 1983; 9:237-40. Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984; 28:293-322. Lembach RG, Keates RH. Aspheric silicone lenses for keratoconus. CLAO J 1984; 10:323-5. McDonald MB, Kaufman HE, Durrie DS, et al. Epikeratophakia for keratoconus. The nationwide study. Arch Ophthalmol 1986; 104: 1294-300. Jensen AD, Maumenee AE. Refractive errors following keratoplasty. Trans Am Ophthalmol Soc 1974; 72:123-31. Troutman RC, Gaster RN. Surgical advances and results of keratoconus. Am J Ophthalmol1980; 90:131-6. Mannis MJ. Indications for contact lens fitting after keratoplasty. CLAO J 1986; 12:225-8. Ruben M, Colebrook E. Keratoconus keratoplasty curvatures and contact lens wear. Br J Ophthalmol1979; 63:268-73. Mannis MJ, Zadnik K, Deutch D. Rigid contact lens wear in the corneal transplant patient. CLAO J 1986; 12:39-42. Genvert GI, Cohen EJ, Arentsen JJ, Laibson PR. Fitting gas-permeable contact lenses after penetrating keratoplasty. Am J Ophthalmol 1985; 99:511-4. Daniel R. Fitting contact lenses after keratoplasty. Br J Ophthalmol 1976; 60:263-5. Paglen PG, Fine M, Abbott RC, Webster RG Jr. The prognosis for keratoplasty in keratoconus. Ophthalmology 1982; 89:651-4.
Abstract: The success rate of contact lens fitting and rate of progression to keratoplasty were evaluated for 115 consecutive patients with keratoconus. Of 190 nonoperated eyes that needed to be fit, 25 (13%) could not be fit, whereas 165 eyes (87%) could be fit. Most of these eyes had been referred for keratoplasty after previous contact lens fittings had no longer been successful. Of the 165 eyes that could be fit, 51 (31 %) ultimately needed keratoplasty after an average of 38.4 months of lens wear, and 114 eyes (69%) did not require keratoplasty over an average follow-up interval of 63 months of wearing contact lenses. The average initial keratoplasty reading in these two groups was 56.8 and 51.8 diopters (D), respectively. Special design, bispheric lenses were required in 125 of these 165 eyes (76%) and frequent lens changes were necessary. Of 88 postoperative eyes, 53 (60%) wore contact lenses for best vision. Keratoplasty can be delayed or avoided in many keratoconus patients by using contact lenses, especially special design, bispheric lenses. Also, keratoconus eyes often need contact lenses after keratoplasty. [Key words: bispheric (Soper-cone) lens, contact lens, keratoconus, penetrating keratoplasty.] Ophthalmology 95:487-492, 1988
Keratoconus is an ectatic corneal disorder characterized by central thinning and protrusion of the central cornea. It is idiopathic in nature and frequently leads to decreased vision. A majority of patients may be visually corrected using spectacles or contact lens fitting. However, epidemiologic studies have shown that 10 to 20% of patients will ultimately require penetrating keratoplasty.l,2 The purpose of this study is (1) to determine the proportion of patients with keratoconus fitted successfully with contact lenses, (2) to determine the proportion of patients who require keratoplasty, (3) to characterize the types and numbers oflenses that are needed to achieve a satisfactory, nonsurgical visual result, and (4) to assess the visual outcome in those undergoing surgery. Originally received: October 19, 1987. Revision accepted: December 29, 1987. From the Contact Lens Service and the Comeal Service, The Wilmer Institute, The Johns Hopkins Medical Institutions, Baltimore. Presented in part at the American Academy of Ophthalmology Annual Meeting, Dallas, November 1987. Reprint requests to Walter J. Stark, MD, Maumenee 327, The Johns Hopkins Hospital, 600 N. Wolfe St, Baltimore, MD 21205.
PATIENTS AND METHODS We reviewed the charts of230 eyes of 115 consecutive patients who reported as new patients to the Cornea Service of the Wilmer Eye Institute from 1977 to 1982 for consideration of penetrating keratoplasty. Inclusion of new patients into this study was truncated at this point, but patients were followed through May 1987 allowing for an adequate follow-up interval for most eyes. Patients were excluded from the study if they presented one time only for evaluation and if the contact lens fitting was not managed by our service. Historic features that were recorded on admission included (1) age, (2) sex, (3) duration of diagnosis of keratoconus, (4) previous experience with contact lens fitting, and (5) the status of the fellow eye. A complete ocular examination was provided, including a manifest refraction, keratometry readings, slit-lamp examination, and dilated fundus examination. For purposes of data analysis, eyes were not averaged in if the mires were too distorted to enable keratometry reading, thus probably underestimating the true average keratometry readings. Many times the recorded reading was the upper limit of the keratometer scale and the actual keratometric reading was probably 487
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higher. In these eyes, the upper limit of the keratometer was used for data analysis, again underestimating the true average keratometry readings. If the patient's visual acuity was not satisfactory with a spectacle correction, an attempt was first made to fit the patient with a spherical hard contact lens. Initially, polymethylmethacrylate (PMMA) lenses were used, but more recently gas-permeable lenses have been used for this purpose. If a hard or gas-permeable spherical lens was not satisfactorily tolerated, a fitting using a soft contact lens was attempted in selected patients. When patients could not tolerate the hard contact lens and were unable to achieve satisfactory vision with soft contact, then a fitting was attempted with a special design, bispheric lens. We used the Soper-cone variety of bispheric contact lenses. Scleral-fitted contact lenses were not used in this study, and successful results with combination lenses and "piggyback" systems were limited during this period. Whenever possible, keratometry readings are obtained and trial lenses are chosen equal to the flattest reading. A best-fit contact lens demonstrates no evidence of air beneath the lens peripherally or centrally so that there is an equal distribution of fluorescein to all corresponding weightbearing areas of the cornea. This may be referred to as three-point touch and to insure the proportion of bearing (touch) to fluorescein is approximately 50% of the total pattern. Careful attention to the doughnut ring width is made to avoid a narrow ring which will diminish tear exchange. It also has been our impression that the Soper lenses work best with corneas steeper than 50 diopters (D). The optimum fit is determined with final variances in diameter to allow stability of the vision and centration of the contact lens. A successful fit was defined as adequate vision and daily contact lens wear for at least 6 months. Eyes that could not be fitted were scheduled for penetrating keratoplasty. Experience with epikeratophakia during this time interval was limited, and epikeratophakia was not performed in this group. The reasons for keratoplasty during our study included poor vision due to central corneal scarring despite a good fit and markedly decreased wearing time due to the inability to continue to maintain a comfortable fit. The reasons for penetrating keratoplasty in the 12 eyes that had undergone surgery before presenting to our service could not be determined. The time from our initial fit to keratoplasty was recorded for the patients who became contact lens-intolerant during the study period. Patients usually presented to our service already carrying the diagnosis of keratoconus, thus the duration from diagnosis to presentation to our service was not accurately quantifiable for many patients. Other data included the types and number of lenses that were needed over the study interval. Often these patients required changes in contact lens parameters for best fit. Therefore, the number of lenses used in these patients was imprecise. For this reason, the range of how many lenses needed for each eye was tabulated and categorized as (1) one or two lenses, (2) three to ten lenses, 488
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and (3) over ten lenses. If a patient progressed from a hard spheric or soft lens to a special design, bispheric lens, the latter was recorded as the most recent lens used. In patients who either had undergone penetrating keratoplasty or subsequently underwent penetrating keratoplasty, postoperative visual acuity, and the method of visual rehabilitation was noted. Manifest refraction and keratometry readings were noted when possible. If contact lenses were used, the type of lenses and reasons for their use rather than spectacles were recorded.
RESULTS Two hundred thirty eyes of 115 consecutive patients were included in this study. The average age was 30.7 years (range, 11-75 years). There were 48 females and 67 males in the study group. The sex distribution and average age were similar for each subgroup analyzed including those who had previously undergone penetrating keratoplasty (31.0 years of age), those who underwent penetrating keratoplasty during follow-up in our study (31.2 years of age), and those who never underwent surgery (30.5 years of age). Upon initial presentation, 12 eyes had undergone previous keratoplasty, the current contact lens was adequate in 15 eyes, and spectacles provided adequate visual function for 13 eyes. The reason patients with lessadvanced keratoconus usually presented was to be fit for a contact lens in their fellow eye. There were 190 eyes that had not been operated on and had been considered to have failed previous contact lens fittings on presentation to our service. Almost all of these patients had been wearing contact lenses previously, but could no longer tolerate their current lens and/or could no longer be satisfactorily fit by their referring physician. At the initial fitting, 165 ofthese eyes (87%) could be successfully fit with a contact lens. Accordingly, a contact lens could not be successfully fit in 25 eyes (13%), and these patients were scheduled for keratoplasty. The keratometry reading was usually not measurable in this group, and when it could be measured was usually greater than 60 D (Table 1). During the follow-up interval, 51 of these 165 eyes (31%) became intolerant of contact lenses despite changing to new lenses, and were subsequently referred for keratoplasty. We termed these patients the prekeratoplasty group, even though this was a retrospective assignment. However, 114 of the 165 eyes (69%) did not require keratoplasty over the follow-up interval, which ranged from 6 to 125 months (average, 62.7 months; median, 60 months). These patients formed our nonkeratoplasty group. NONKERATOPLASTY GROUP
There were 114 eyes that did not require keratoplasty during an average follow-up interval of 62.7 months (Table 2). Of these eyes, 58 (51 %) required one or two different lenses, 52 (46%) required three to ten different
SMIDDY et al
lenses, and four (4%) required more than ten different lenses during the follow-up period (Table 3). The special design, bispheric lens was necessary in 82 of these 114 eyes (72%), whereas spherical (PMMA or gas-permeable) lenses were fit for 32 eyes (28%) (Table 4). Soft contact lenses were not the final lens for any patient although three patients in the study derived enough benefit that they wore them at some point during the study interval. In the few patients who used them, they either were not visually successful or a subsequent special design, bispheric lens was fit. The visual acuity was 20/40 or better with the contact lenses in 88 of these 114 eyes (77%),20/50 to 20/100 in 23 eyes (20%), and 20/200 or worse (due to a previous retinal detachment, amblyopia, and optic neuropathy) in 3 eyes (3%). The visual acuity while wearing contact lenses was 20/20 to 20/40 in 88 of the 114 nonkeratoplasty eyes (77%),20/50 to 20/100 in 23 eyes (20%), and 20/200 or worse in 3 eyes (3%). Keratometry readings were taken at initial presentation in all patients and are summarized in Table 1. For the nonkeratoplasty group, the average reading was 51.8 D. The average initial keratometry reading was at least 50.0 in over one half of these patients.
PREKERATOPLASTYGROUP Of the 165 eyes that were initially successful in the contact lens fitting, 51 required keratoplasty (31 %) an average of 38.4 months (median, 36 months) after the initial fitting (Table 2). This represents a 42% cumulative lO-year-risk of needing a penetrating keratoplasty after an initially successful contact lens fitting (Fig 1). It must be reiterated that this was a highly selected population, since most patients presented well after the initial diagnosis of keratoconus, typically after contact lens fittings elsewhere were no longer successful. Many of the patients needing keratoplasty had poor vision despite a good contact lens fitting and thus would be poor candidates for epikeratophakia. However, most keratoplasties were performed for inability to maintain a good-fitting contact lens. During the follow-up interval in this group of patients, one or two contact lenses were fit before the eye became intolerant of contact lenses in 17 eyes (33%), three to ten lenses were necessary in 27 eyes (53%), and more than ten contact lens changes were necessary in 7 eyes (14%) (Table 3). Before keratoplasty, the special design, bispheric variety lens was successfully fit in 43 of these eyes (84%), usually at presentation (Table 4). Eight of the 51 prekeratoplasty eyes (16%) either could not be fit at all or could not wear the lens for at least 6 months (our criterion for successful fit). Eyes in the nonkeratoplasty group usually required several lens changes, but not as many as in the prekeratoplasty group, as might be expected (Table 3). Similarly, special design, bispheric lenses were used frequently in the nonkeratoplasty group (72%), but were required more frequently in the prekeratoplasty group (84%) (Table 4).
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Table 1. Range and Average of Keratometric Readings Group (no. of eyes) CNF
Prekeratoplasty*
Nonkeratoplastyt
Average (0) Range (0) Too distorted 260 55-59 50-54 <50 Not available
59.2
56.8
51.8
7 6 2 0 1 9
3 22 7 9 9 1
0 21 20 19 52 2
Total eyes
25
51
114
CNF = could not fit on initial presentation; 0 = diopters. * Eyes that required keratoplasty during the study period. t Eyes that did not require keratoplasty during the study period.
Table 2. Follow-up and Results of 165 Patients with Initially Successful Contact Lens Fitting Follow-up Interval (mo)
Group
No. of Patients
(%)
Average
Range
Pre keratoplasty Nonkeratoplasty
51 114
(31) (69)
38.4' 62.7
6-125 6-125
Total
165
, Average interval to keratoplasty.
Table 3. Number of Lenses for Keratoconus Eyes No. of Eyes No. of Lenses
Nonkeratoplasty
Prekeratoplasty
(%)
Total (%)
58 (51) 52 (46) 4 (4)
17 (33) 27 (53) 7 (14)
75 (45) 79 (48) 11 (7)
(%)
<3 3-10 >10 Total
114
51
165
Postkeratoplasty
(%)
52 (98) 1 (2) 0(0) 53
Table 4. Types of Lenses for Keratoconus Eyes No. of Eyes Types of Lenses
Nonkeratoplasty
Pre keratoplasty
(%)
Total (%)
Bispheric Spherical hard
82 (72) 32 (28)
43 (84) 8 (16)
125 (76) 40 (24)
51
165
Total
(%)
114
489
OPHTHALMOLOGY
-~§ u
2
c:
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APRIL 1988
1.0 0.9 0.8 0.7
0
~
cu
c:
0.6
~ '0
0.5
E
UI
0.4
'0
0.3
.2
0.2
~ cu
-... c:
n=/65eyes
0
e Q.
0.1
0..
Months follow-up
Fig 1. Cumulative proportion of eyes maintained on contact lenses.
Table 5. Method of Visual Rehabilitation and the Reasons for Contact Lens Use in Eyes after Keratoplasty for Keratoconus Type of Visual Rehabilitation (no. of eyes) Reasons for Contact Lens Wear
Spectacles
Spherical Contact Lenses
Bispheric Contact Lenses
Total (%)
High astigmatism Anisometropia Irregular astigmatism Other
4 0
10 2
13 7
27
0 31
3 10
8 0
11 41
Total (%)
35 (40)
25 (28)
28 (32)
9
88 (100)
The average keratometry reading at initial presentation for this group was 56.8 D, and was at least 55 Din over one half of the eyes (Table 1).
POSTKERATOPLASTYGROUP A total of 88 eyes from this group had a keratoplasty at or after initial presentation. Twelve eyes had already had penetrating keratoplasty, 25 could not be fit initially and were scheduled for corneal transplantation, and 51 later required keratoplasty when they became intolerant to contact lens wear. The latter 76 eyes had surgery by one of us (WJS). Postoperative follow-up period averaged 54 months (range, 3-228 months) and lasted for at least 12 months in 81 of these 88 eyes. One patient had an episode of graft reaction during follow-up that cleared with treatment. 490
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Of these 88 eyes, 35 (40%) were visu~lly rehabilitated with spectacles. Contact lenses were fit in the remaining 53 eyes. Patients required postkeratoplasty contact lens fitting because of (1) postoperative astigmatism, (2) anisometropia from coexisting or induced myopia or aphakia, and (3) objectively or (4) subjectively improved vision over that obtained with spectacles (Table 5). Some patients in the third group probably achieved a better quality of vision due to neutralization of irregular, although low astigmatism. Many of those in the fourth group seemed primarily to be wearing the contact lenses out of convenience, since most patients wore contact lenses in the fellow eye and were experienced enough at wearing contact lenses to desire to wear them despite a marginal visual improvement. The postoperative astigmatism averaged 4.5 D, (range, 0-12 D), was 5.0 D or less in 61 of these 88 eyes (69%), and was more than 5.0 Din 27 eyes (31%). Four of the 27 eyes with high astigmatism have a visual acuity of at least 20/25 with about 5.0 D of cylinder in their spectacles. Two of these patients are 6 months postoperative and may eventually desire contact lenses with longer follow-up and after suture removal. These two patients wore contact lenses for 5 years before becoming intolerant of them and needed keratoplasty. All such eyes except these two have at least 1 year of follow-up after keratoplasty. The other 23 eyes were fit with contact lenses including special design, bispheric lenses in 13 eyes and spherical hard lenses in 10 eyes. Of the 61 postkeratoplasty eyes with 5.0 D or less of astigmatism, 30 wear contact lenses postoperatively including special design, bispheric lenses in 15 eyes and spherical hard lenses in 15. The reasons for contact lens use over spectacles in this group include anisometropia (preexisting or induced high myopia or aphakia) in 9 eyes, three or more Snellen lines better vision with contact lenses (due to neutralization of irregular astigmatism) in 11 eyes, and subjectively better vision in 10 other eyes. Eyes in the last group had 2.0 D or less of cylinder and an improvement of two Snellen lines with contact lenses. Nevertheless, the subjective visual improvement motivated these patients to wear contact lenses. This was probably easier for this group of patients since they were experienced contact lens wearers and usually had a greater visual benefit from the contact lens worn in the fellow eye. Indeed, 68 of the 88 fellow eyes (77%) of these patients were wearing contact lenses. The visual results were excellent. The corrected visual acuity was 20/20 or better in 48 of88 eyes (55%),20/25 to 20/40 in 31 eyes (35%), 20/50 to 20/200 in 8 eyes (9%), and limited to hand motions in 1 eye with optic neuropathy unrelated to surgery. The visual acuity with best manifest refraction was compared with the best visual acuity with contact lenses for the 53 patients who wore lenses after keratoplasty. This was not possible in seven eyes because of the inability to accurately refract these patients who typically had high or irregular astigmatism. In the 46 patients in whom a comparison was possible, there was an average 2.4 lines of improvement over spectacle correction with the contact lenses. The
SMIDDY et al
change in Snellen lines was zero in 13 eyes, one or two lines in 16 eyes, three or four lines in 9 eyes, and five or more lines in 8 eyes. Many patients had significant subjective improvements when the degree of astigmatism was higher, despite good visual acuity by manifest refraction.
DISCUSSION Most patients with keratoconus do not require penetrating keratoplasty, but 10 to 20% do come to keratoplasty.I,2 Contact lens fitting has improved the visual quality in many of these patients thereby delaying or preventing penetrating keratoplasty. Efforts at improving contact lens fitting techniques and materials could decrease the proportion of patients who requi~ surgical intervention. A variety of contact lens modalities have been used and developed to attain this goal. Many patients can be fit with rigid, non-gas-permeable spherical lenses, and their quality of vision frequently can be markedly improved. 3 A variety of scleral contact lenses also have been used with success rates of 85%.4,5 Semiflexible contact lenses,6 soft contact lenses,1-IO and a variety of more sophisticated contact lens fitting techniques such as the lens-lid attachment technique, II "piggyback" systems combining hard and soft lenses, 12 and the Saturn lens (combining soft and hard components in a single lens) have had limited success in our experience. More recently, a large number of patients have had success with gas-permeable rigid lens materials. 13-18 For patients with more marked astigmatism because of keratoconus and for those who have become intolerant to other contact lens modalities, the special design, bispheric contact lens (such as the Soper-cone lens)18 or aspheric lenses l9 are the only nonsurgical alternatives. It must be emphasized that this study population is a highly selected group and is not comparable with other published series of unselected patients. The degree of advanced keratoconus is evidenced by the distribution of keratometric readings in these eyes (Table 1). From this table, it is evident that of the 57 eyes with an initial keratometry reading between 50 and 60 D, 55 eyes (98%) were initially fit with a contact lens, and 39 eyes (68%) were maintained on contact lenses throughout the duration of the study. Most patients were referred when keratoplasty was being contemplated since contact lens fitting attempts were no longer successful. In an unselected population, contact lens fitting success rates would be expected to be higher. This study demonstrates that even a majority of these patients with advanced keratoconus can be successfully fit, and special design, bispheric lenses are frequently necessary. As might be expected, the degree of success correlated with the value of the keratometry reading, yet even the nonkeratoplasty group had fairly high keratometry readings. For many of these patients, this may require numerous follow-up visits with a large number of contact lens fittings over a long period of time. Although the costs of contact
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KERATOCONUS
lenses and repeated follow-up visits are not negligible, they compare favorably with those involved with even an uncomplicated surgical admission. More importantly, possible complications may be avoided. However, successful wear requires significant commitment on the part of the patients and the contact lens filter, but those undergoing keratoplasty require at least a similar degree of care and commitment. Initial results of epikeratophakia for keratoconus without corneal scarring have been encouraging,20 but penetrating keratoplasty remains the most common surgical alternative once contact lenses can no longer be fit. Further studies that clearly define equivalency of preoperative groups and at least equal postoperative results are needed before epikeratophakia becomes the treatment of choice. Most patients desire keratoplasty when they cannot be fit for contact lenses any longer or when the vision is not improved with the contact lenses because of corneal scarring. Some patients may expect that the surgical intervention will obviate the need for future contact lens wear, and may therefore desire surgery despite being able to be corrected successfully with a contact lens. Surgeons should caution patients with this misconception. In this study, 60% of eyes that underwent keratoplasty wear contact lenses postoperatively for best vision. In addition, many require a special design, bispheric lenses for best vision after keratoplasty. Refractive errors after keratoplasty remain a limiting factor in the success of penetrating keratoplasty,21,22 but contact lenses can be fit with a high degree of success after keratoplasty.9,23-27 Although astigmatism or anisometropia are the reason for contact lens use in about one half of these eyes, many patients wear the contact lenses for a subjective or marginal objective improvement in vision over spectacles. These patients are experienced with using contact lenses and usually wear a contact lens in their fellow eye. Many of those experiencing an objective improvement in vision probably benefit from neutralization by the rigid lens of irregular astigmatism. In a sizable proportion of eyes (28 of 53 eyes wearing lenses), special design, bispheric lenses provide the best fit and vision after keratoplasty. This may be because these lenses provide a larger peripheral flange to stabilize the contact lens on the host eye's peripheral corneal curvature. We prefer not to use larger than an 8.0 mm donor button to minimize the antigen load transplanted, thereby theoretically decreasing the risk of subsequent corneal graft rejection. The recipient bed is smaller by 0.25 or 0.50 mm depending on the presence of a crystalline lens. The most encouraging finding of this study is that most patients with keratoconus can maintain excellent vision with spectacles or contact lenses thereby avoiding surgery, despite the highly selected nature of these patients. With careful and persistent contact lens fitting and follow-up, keratoplasty can be delayed or avoided in many patients with keratoconus. This was the case in 69% of eyes in our highly selected patient group over a follow-up interval that averaged 5 years. This represents 491
OPHTHALMOLOGY
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a 58% cumulative lO-year "survival" rate (Fig. 1). The rate of keratoplasty in an unselected group should be much lower. Keratoplasty should not be recommended when contact lenses can be effectively worn with good vision, since most patients will obtain their best postkeratoplasty vision with contact lenses. However, for patients who do require penetrating keratoplasty the surgical results for patients with keratoconus are very encouraging22,28 and in the 88 eyes that had penetrating keratoplasty in this study, the postoperative visual acuity was 20/40 or better in 90% of eyes.
•
12. 13. 14. 15. 16. 17.
REFERENCES
18.
1. Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epiderniologic study of keratoconus. Am J Ophthalmol1986; 101:267-73. 2. Cohen EJ, Parlato CJ. Fitting polycon lenses in keratoconus. Int Ophthalmol Clin 1986; 26(1):111-7. 3. Carney LG. Contact lens correction of visual loss in keratoconus. Acta Ophthalmol 1982; 60:795-802. 4. Gould HL. Management of keratoconus with corneal and scleral lenses. Am J Ophthalmol1970; 70:624-9. 5. Hefny W, Rahim MH. Corneal contact lenses in management of keratoconus. Bull Ophthalmol Soc Egypt 1970; 63:291-3. 6. Gasset AR, Lobo L. Dura-T semiflexible lenses for keratoconus. Ann Ophthalmol1975; 7:1353-7. 7. Koliopoulos J, Tragakis M. Visual correction of keratoconus with soft contact lenses. Ann Ophthalmol1981; 13:835-7. 8. Lundh RL. Keratoconus: a disease that can be treated with soft lenses. Ophthalmologica 1978; 176:34-8. 9. Tragakis MP, Brown SI. Hydrophilic contact lenses for correcting irregular and high astigmatism. Arch Ophthalmol1972; 88:596-601. 10. Hull DS, Hyndiuk RA, Chin GN, Schultz RO. Clinical experience with the therapeutic hydrophilic contact lens. Ann Ophthalmol 1975; 7:555-62. 11. Mackie IA. Management of keratoconus with hard comeallenses: the
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27. 28.
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lens lid attachment technique. Trans Ophthalmol Soc UK 1977; 97:131-5. Buxton IN. Contact lenses in keratoconus. CLAO J 1978; 4(3):7485. Rosenthal P. The Boston Lens and the management of keratoconus. Int Ophthalmol Clin 1986; 26(1):101-9. Raber 1M. Fitting cellulose acetate butyrate lenses in keratoconus. Int Ophthalmol Clin 1986; 26(1):91-9. Maguen E, Espinosa G, Rosner IR, Nesburn AB. Long-term wear of Polycon contact lenses in keratoconus. CLAO J 1983; 9:57-9. Mobilia EF, Foster CS. A one-year trial of Polycon lenses in the correction of keratoconus. CLAO J 1979; 5(3):37-42. Raber 1M. Use of CAB Soper cone contact lenses in keratoconus. CLAO J 1983; 9:237-40. Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984; 28:293-322. Lembach RG, Keates RH. Aspheric silicone lenses for keratoconus. CLAO J 1984; 10:323-5. McDonald MB, Kaufman HE, Durrie DS, et al. Epikeratophakia for keratoconus. The nationwide study. Arch Ophthalmol 1986; 104: 1294-300. Jensen AD, Maumenee AE. Refractive errors following keratoplasty. Trans Am Ophthalmol Soc 1974; 72:123-31. Troutman RC, Gaster RN. Surgical advances and results of keratoconus. Am J Ophthalmol1980; 90:131-6. Mannis MJ. Indications for contact lens fitting after keratoplasty. CLAO J 1986; 12:225-8. Ruben M, Colebrook E. Keratoconus keratoplasty curvatures and contact lens wear. Br J Ophthalmol1979; 63:268-73. Mannis MJ, Zadnik K, Deutch D. Rigid contact lens wear in the corneal transplant patient. CLAO J 1986; 12:39-42. Genvert GI, Cohen EJ, Arentsen JJ, Laibson PR. Fitting gas-permeable contact lenses after penetrating keratoplasty. Am J Ophthalmol 1985; 99:511-4. Daniel R. Fitting contact lenses after keratoplasty. Br J Ophthalmol 1976; 60:263-5. Paglen PG, Fine M, Abbott RC, Webster RG Jr. The prognosis for keratoplasty in keratoconus. Ophthalmology 1982; 89:651-4.