Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) Scleral Device Compared to Keratoplasty for the Treatment of Corneal Ectasia KAREN S. DELOSS, NADEEM H. FATTEH, AND CHRISTOPHER T. HOOD PURPOSE:
To compare the ocular characteristics and visual outcomes of eyes with corneal ectasia that were fitted with the Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) scleral device to those that underwent keratoplasty. DESIGN: Retrospective, comparative case series. METHODS: We reviewed the charts of consecutive patients with corneal ectasia that were evaluated for PROSE or underwent keratoplasty at our institution. Clinical data, topographic indices, and corneal thickness were reviewed, and eyes were stratified according to the Amsler-Krumeich classification for severity of ectasia. Only the more severe eye of each patient was included in the study. We compared visual acuity before and after PROSE fitting or keratoplasty. For PROSE evaluations, achievement of satisfactory fit and continued wear at 1 year of follow-up were recorded. RESULTS: From 2010 to 2012, 36 patients underwent PROSE evaluation for corneal ectasia while 37 patients underwent keratoplasty for the same indication. All eyes were successfully fitted with the PROSE device. Eyes in the keratoplasty group had more severe ectasia than eyes in the PROSE group (P [ .038). Visual acuity was achieved more rapidly in the PROSE cohort compared to keratoplasty, and mean visual acuity was significantly better for all eyes (P < .0001) and when including only eyes with stage 4 ectasia (P < .001). More eyes with stage 4 ectasia achieved 20/25 visual acuity after PROSE than after keratoplasty (P [ .003). At 1 year follow-up in the PROSE cohort, Snellen acuity was 20/28 (P [ .108 vs keratoplasty), improving to 20/25 with over-refraction (P [ .006 vs keratoplasty). CONCLUSIONS: Eyes with advanced corneal ectasia can be successfully fitted with the PROSE device, and the visual acuity outcome for stage 4 ectasia was better and more rapid compared to keratoplasty. The acuity remained excellent with 1 year of follow-up. PROSE Accepted for publication Jul 15, 2014. From the University of Michigan W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan. Nadeem H. Fatteh is currently at Kresge Eye Institute, Wayne State University, Detroit, Michigan. Inquiries to Christopher T. Hood, University of Michigan Kellogg Eye Center, 1000 Wall St, Ann Arbor, MI 48105; e-mail: hoodc@med. umich.edu
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evaluation should be considered in patients with advanced corneal ectasia before proceeding to keratoplasty, especially if the ectasia is deemed stable. (Am J Ophthalmol 2014;158:974–982. Ó 2014 by Elsevier Inc. All rights reserved.)
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keratoconus (KCN), pellucid marginal degeneration, and ectasia after laser in situ keratomileusis (LASIK), may be reduced because of both irregular astigmatism and corneal scarring,1–3 and management primarily consists of optical correction to maximize visual function.4 Although most patients with ectasia can be managed with spectacles and contact lenses,4–7 12%–20% of patients with keratoconus will progress to corneal transplantation because of difficulty achieving satisfactory vision or comfort with contact lenses.4,6,8 Although keratoplasty is often successful in increasing visual acuity,9–13 the potential exists for significant intraoperative and postoperative morbidity,14 especially given the expected survivorship of patients with KCN.15 Recently, large-diameter lenses that vault the cornea and limbus and rest on the sclera have emerged as a treatment option to improve the visual function of patients with severe corneal ectasia.5,16–20 The Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) is a customfitted device developed at the Boston Foundation for Sight (Needham, Massachusetts, USA) to restore vision, reduce symptoms, and improve quality of life for patients suffering from complex corneal disease including corneal ectasia. Other authors have previously described use of the PROSE device to improve visual function of patients with corneal ectasia whose vision is not adequately corrected with spectacles or other types of contact lenses,17,18,20,21 and it has been suggested that many of these patients may otherwise require corneal transplantation. However, no previous studies have evaluated the success of the PROSE device based on the severity of corneal ectasia, or directly compared PROSE patients to those who underwent corneal transplantation. Therefore, the purpose of the current study was to compare the demographics, ocular characteristics, and visual outcomes of consecutive eyes with corneal ectasia referred for PROSE evaluation at our institution to consecutive eyes with corneal ectasia that underwent keratoplasty during the same time period.
ELSEVIER INC. ALL
RIGHTS RESERVED.
0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2014.07.016
MATERIALS AND METHODS THE UNIVERSITY OF MICHIGAN INSTITUTIONAL REVIEW
Board approved this retrospective study, which was conducted in accordance with the tenets of the Declaration of Helsinki guidelines and all applicable federal and state laws. We included consecutive eyes from January 2010 to December 2012 that were referred for PROSE evaluation for corneal ectasia, or that underwent keratoplasty for the same indication during the same time period, at the W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA. For the current study, corneal ectasia included a clinical diagnosis made by a fellowship-trained corneal specialist of KCN, pellucid marginal degeneration, or post-LASIK ectasia. All PROSE evaluations and fittings were completed by 1 provider (K.D.) who completed a PROSE clinical fellowship at the Boston Foundation for Sight. For each patient, only the eye with more severe ectasia was included in this study. Five surgeons performed the corneal transplants, with surgical technique varying according to surgeon preference; both penetrating keratoplasty (PKP) and deep anterior lamellar keratoplasty (DALK) were included. The decision to pursue PROSE evaluation or keratoplasty was at the surgeon’s discretion. From the medical records we recorded the corrected distance visual acuity (CDVA), including the method used to achieve the acuity, in the 3 months prior to PROSE evaluation or keratoplasty. We also recorded habitually corrected visual acuity (HCVA), defined as the visual acuity in correction that a patient utilized on a regular basis. This term was defined since some patients with corneal ectasia can refract better with spectacle correction but cannot tolerate the full prescription, or can achieve improved acuity with a contact lens but are unable to wear it because of comfort or fit. Topographic indices including average central keratometry, and simulated minimum and maximum keratometry as measured by Humphrey Atlas 993 corneal topographer (Carl Zeiss Meditec, Jena, Germany), Orbscan IIz (Bausch and Lomb, Rochester, New York, USA), or Pentacam HR (Oculus, Wetzlar, Germany) at the time of clinical evaluation, were recorded. Apical corneal thickness as assessed by ultrasound pachymetry (Pachette 2; DGH Technology Inc, Exton, Pennsylvania, USA), Orbscan IIz, or Pentacam HR, was also recorded. In order to assess the severity of corneal ectasia, we used the Amsler-Krumeich classification22,23 (Table 1), which uses the refraction, clinical findings on slit lamp examination, corneal curvature, and corneal thickness. For eyes that underwent successful PROSE fitting, we recorded the number of visits and the length of time needed to achieve a fit, as well as visual acuity after completion of the fitting process and at 1 year of follow-up. Assessment of continued wear was determined at the 1 year follow-up visit by patient-reported number of hours of average wear time
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TABLE 1. Amsler-Krumeich Classification for Staging Keratoconus Stage 1 Eccentric steepening Myopia, induced astigmatism, or both 55.00 D Central corneal scarring Minimum corneal thickness 200 mm D ¼ diopters. A single criterion is necessary for inclusion in a stage.
per day. Complications related to PROSE wear were recorded. For eyes in the keratoplasty group, complications as well as CDVA with method to achieve acuity at 3, 6, 9, and 12 months postoperatively were recorded. Comparisons between the demographics, ocular characteristics, and visual outcomes of both groups were made using 2-tailed t tests and Fisher exact test. Snellen acuity was converted to logarithm of the minimal angle of resolution (logMAR) for statistical analysis. All statistical analyses were performed with a Microsoft Office Excel statistical package (Redmond, Washington, USA) with a P value 60 diopters (D) (n ¼ 10), mean visual acuity was 20/25 after PROSE fitting. Figure 3 displays the percentage of all eyes, as well as stage 4 eyes only, that achieved 20/40 or 20/25 Snellen acuity. There were no significant differences in the percentage of eyes that attained 20/40 acuity between the PROSE and keratoplasty cohort. However, the PROSE group had a higher percentage of eyes with 20/25 acuity when considering all eyes, as well as those with stage 4 ectasia (P ¼ .001 and P ¼ .003, respectively). Figure 4 displays the visual acuity over time after PROSE evaluation or keratoplasty. After keratoplasty, mean acuity continued to improve until the 12-month follow-up visit. The mean spherical equivalent spectacle correction was 1.68 D 1 year after keratoplasty, with 3.04 D of refractive astigmatism; 10 patients (27%) required an RGP to achieve their best acuity. PROSE device fitting took 2.38 6 1.41 months and 6.49 6 2.13 visits, at which time best acuity was achieved. One year of follow-up was available for 34 patients fitted for PROSE; of those, 5 patients had discontinued device wear. Two discontinued wear because of unsatisfactory vision, 1 had difficulty inserting and removing the device, 1 had irregular sleeping habits that prevented device wear, and 1 had acute corneal hydrops. If the 2 patients who did not return for follow-up were assumed to have discontinued wearing PROSE, the success rate for continued wear at 1 year would be 80.6% (29/36). In the 29 patients that were still wearing PROSE at 1 year, the average wear time was 13.0 6 3.3 hours per day and the mean acuity was 20/28 (P ¼ .108 vs keratoplasty), improving to 20/25 with over-refraction (P ¼ .006 vs keratoplasty). Eight of 10 eyes with mean keratometry >60 D
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TABLE 3. Amsler-Krumeich Severity in the PROSE and Keratoplasty Cohorts PROSE (N ¼ 36)
Amsler-Krumeich stage, n (%) Stage 1 Stage 2 Stage 3 Stage 4
Keratoplasty (N ¼ 37)
P Value
.038 0 5 (13.9%) 6 (16.7%) 25 (69.4%)
0 0 4 (10.8%) 33 (89.2%)
PROSE ¼ Prosthetic Replacement of the Ocular Surface Ecosystem.
were wearing PROSE at 1 year; mean acuity was 20/35, improving to 20/30 with over-refraction. There were 1 intraoperative and 5 postoperative complications related to keratoplasty (16.2%). One patient had a partial expulsion of the crystalline lens secondary to a Valsalva maneuver. Postoperatively, a dense white cataract developed with vision limited to light perception, and the patient is scheduled to undergo cataract surgery. Three patients had episodes of graft rejection that resolved with frequent application of topical corticosteroids. One patient developed broad peripheral anterior synechiae and elevated intraocular pressure. Another patient developed a suture abscess that required application of cyanoacrylate glue for a microperforation. No complications of PROSE device wear were noted.
DISCUSSION IN THIS RETROSPECTIVE COMPARATIVE CASE SERIES ALL
candidate eyes with corneal ectasia could be successfully fitted with the PROSE device, regardless of corneal steepness, thinning, or presence of opacity. Visual outcomes for eyes with stage 4 ectasia, as graded by the AmslerKrumeich classification, were better and visual rehabilitation was more rapid after PROSE fitting compared to keratoplasty. With 1 year of follow-up, some patients discontinued wearing the PROSE device, and mean visual acuity declined slightly but still remained excellent. Our results suggest that even in cases of advanced ectasia, PROSE evaluation should be considered before keratoplasty, especially if the ectasia is deemed stable and unlikely to progress. Optical correction to increase visual functioning in patients with corneal ectasia needs to address myopia, irregular astigmatism, and corneal scarring.1–3 Scleral lenses are unique in that they vault the cornea to mask high amounts of astigmatism and rest on the less innervated sclera, providing better comfort. Among scleral lenses, PROSE is unique because each device is custom designed VOL. 158, NO. 5
FIGURE 1. Scatterplot of visual acuity of all eyes before and after PROSE fitting or keratoplasty. HCVA [ habitually corrected visual acuity.
by the fitter using proprietary computer-aided design and manufacturing software, employing spline functions, that is linked to a high-precision, high-resolution, computerized lathe. Additionally, PROSE incorporates wavefrontguided optics to correct higher-order aberrations, which may contribute to increased visual acuity tolerance and enhanced vision.24 The fitting process for the PROSE device has previously been described.25,26 Other authors have described the use of scleral lenses, including the PROSE device, for improvement in vision and function in patients with corneal ectasia,5,16,17,19,20,26 but no authors have quantified the severity of ectasia, compared outcomes to those after surgery, or presented long-term follow-up. Most eyes in our study had severe ectasia (stage 3 or 4) according to the Amsler-Krumeich classification, with more severity in the keratoplasty cohort compared to the PROSE cohort. Our results for visual outcomes compare favorably to other reported studies with the PROSE device, and, similarly to previous studies, we also report HCVA,20,26 since it more accurately characterizes the acuity that the patient utilizes on a daily basis. In our study, Snellen-equivalent visual acuity improved from worse than 20/200 at baseline to better than 20/25 after PROSE fitting; a similar improvement occurred when considering only eyes with stage 4 ectasia. In their recent series, Lee and associates reported an improvement from Snellen equivalent 20/94 to 20/24 in keratoconic patients fitted with PROSE,20 while Baran and associates reported an improvement from 20/73 to 20/25.18 Other authors have reported that 87%–93% of patients with keratoconus achieve 20/40 or better acuity with scleral lenses.18,19,27 In our study, 100% of eyes with stage 4 ectasia achieved 20/40 or better acuity, and 80% of eyes achieved 20/25 or better acuity. Comparing only eyes with stage 4 ectasia, mean visual acuity as well as percentage of eyes achieving 20/25 acuity was significantly better after PROSE fitting compared to keratoplasty. Additionally, owing to high and irregular astigmatism, 10 eyes (27%) needed an RGP after keratoplasty to achieve optimal acuity, consistent
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FIGURE 2. Mean visual acuity of all eyes (Top) and stage 4 eyes only (Bottom) at baseline and after PROSE fitting or keratoplasty. The standard error bars are displayed. CDVA [ corrected distance visual acuity (obtained in office); HCVA [ habitually corrected distance visual acuity; *P < .0001, **P < .001.
with previously published reports28,29; 6 discontinued RGP wear owing to lens intolerance. At 1 year, the majority of patients were still wearing PROSE with excellent acuity. However, some patients that initially achieved a satisfactory fit were no longer wearing the device and the mean acuity declined slightly. Acuity was still significantly better than keratoplasty if the power of the device was modified based on over-refraction. 978
A hypothetical advantage of scleral lenses is that fewer modifications of power should be needed with ectasia progression, since the cornea is completely vaulted by sterile saline; it is not entirely clear why power changes are necessary if the cornea remains vaulted, and further investigation in the area is warranted. Of note, 1 patient with mean keratometry >60 D underwent acute corneal hydrops, underscoring that fact that ectasia progression
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FIGURE 3. Percentage of eyes achieving 20/40 or better acuity (Top) or 20/25 or better acuity (Bottom) after PROSE fitting or keratoplasty.*P < .05, **P [ .001, ***P [ .003.
can still occur while wearing PROSE and suggesting that DALK should be considered in patients with advanced keratoconus deemed at risk for progression. This could avoid the need for a future PKP and the associated higher risk of graft rejection and endothelial cell loss.30 All eyes in our study that underwent PROSE evaluation had previously failed other methods of vision correction, yet all were successfully (when defined as objective and subjective improvement in visual acuity with a comfortable fit) VOL. 158, NO. 5
fitted with PROSE. Importantly, no eyes were excluded because of corneal thinning, opacity, or steepness. However, some patients still discontinued PROSE device wear. Baran and associates were also successful in fitting PROSE for all candidate eyes with ectasia, and reported continued device use in 88% of eyes.18 Lee and associates reported an 82% successful fitting rate. Interestingly, 2 patients in our series discontinued PROSE wear because of unsatisfactory vision, despite achievement of 20/20 acuity; 1 was the
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FIGURE 4. The rate of visual recovery after PROSE fitting or keratoplasty. For keratoplasty, acuity is displayed at standard postoperative visits. For PROSE, fitting took an average of 2.4 months, at which time best-corrected acuity with the device was achieved.
only patient in the PROSE cohort to have intrastromal corneal ring segments. It is possible that significant uncorrected higher-order aberrations from the posterior cornea led to dissatisfaction with vision,31 but this was not investigated in the current study. In our study, only 1 patient underwent PROSE evaluation but elected to proceed with keratoplasty, while 2 declined evaluation and 1 did not proceed owing to lack of insurance coverage, despite qualifying for financial assistance from the Boston Foundation for Sight. Of the remaining patients in the keratoplasty group, we suspect that a referral was not made because of axial corneal scarring that was presumed to limit visual acuity. However, many patients classified as stage 4 ectasia because of corneal scarring were able to achieve excellent visual acuity with PROSE, suggesting that neutralization of high and irregular astigmatism with the device mitigates the visual significance of some scarring and may delay or avoid the need for keratoplasty. CDVA was achieved more rapidly after PROSE fitting compared to keratoplasty. Our results are consistent with those of other authors that have reported that approximately 6 visits are needed to achieve successful PROSE treatment19,20; in our study, these visits occurred over approximately 2.5 months. Because of a paucity of PROSE providers nationwide, many patients fitted at our institution travel a significant distance, and travel planning sometimes determines the frequency of the fitting visits. CDVA after keratoplasty continued to improve until the 1-year time point, consistent with other published results.32 The potential for more rapid visual rehabilitation after PROSE fitting compared to keratoplasty has implications in the young, working patient population that often presents with ectasia. 980
No significant differences were observed in keratometric data between the PROSE and keratoplasty cohorts; however, we recognize the groups are likely not equivalent for a number of reasons. First, owing to variations in practice patterns between the corneal specialists, measurement with a tomographic device was not performed on many eyes that underwent keratoplasty, limiting the number of accurate measurements in this group and biasing the results toward less severe ectasia. Even with advanced tomographic devices, data were unobtainable for many eyes, given the severity of ectasia. We also recognize there is also an inherent bias in comparing 2 groups that are dictated by physician decision (ie, referral for PROSE vs keratoplasty). Acknowledging these limitations, we classified ectasia using a standard system to attempt to make comparison more appropriate. A limitation of the current classification system for corneal ectasia is that it does not stratify patients beyond stage 4, restricting the ability to discriminate amongst the most severe cases. To overcome this, we report the outcomes of eyes more severe than the current classification system (mean keratometry >60 D) that underwent PROSE fitting. For all eyes fitted for PROSE, high disease severity is reflected by an average mean simulated keratometry of 56.49 6 8.92 D. Although data from multiple devices were averaged for keratometry, the slight variability is likely not clinically significant in steep and irregular corneas.33 An additional reason to consider PROSE for patients with ectasia is the potential morbidity associated with keratoplasty, given the lengthy expected survivorship of these patients.15 Although the rate of a clear graft after penetrating keratoplasty for keratoconus is reported to be up to 89% at 10 years,14 there are numerous potential intraoperative and postoperative complications, including graft rejection, graft failure, glaucoma, suture-related infections, and open globe injury.14 There is no risk of endothelial immune rejection after DALK, but other unique complications exist, such as a postoperative Descemet membrane detachment and reduced acuity because of opacification at the interface.34 In our series, 16% of eyes (6/37) had a complication related to keratoplasty, 3 of which could be considered serious, with potential long-term sequelae. We did not encounter any complications related to PROSE wear. To our knowledge, there are no published reports on the rate of complications associated with PROSE wear, including bacterial keratitis, and this should be an area of further study. The main strength of our study is that we compared consecutive eyes with ectasia that underwent PROSE evaluation to those that underwent keratoplasty using a standardized classification system with 1 year of follow-up. We also included only 1 eye from each patient, assuring independence of our data points. We are limited, however, by our relatively small sample size and the retrospective nature of our study. Our assessment of visual acuity was Snellen acuity under standard clinic conditions, which does not assess high-contrast and low-contrast visual acuity that
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may be decreased in patients with ectasia.35 We did not compare visual results to those of other commercially available contact lenses. We did not objectively evaluate patient visual functioning or comfort, although others have demonstrated improved visual functioning of patients fitted with the PROSE device,26 as well as after keratoplasty.36 In summary, we demonstrate successful visual rehabilitation using the PROSE device in eyes with severe ectasia,
with better acuity and more rapid visual rehabilitation compared to eyes that underwent keratoplasty. Excellent acuity was maintained at 1 year in the PROSE cohort. Further prospective comparative clinical studies are warranted, but PROSE evaluation should be considered in contact lens–intolerant patients, especially those with stable ectasia, as surgery may be able to be delayed or even avoided.
ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST and none were reported. The authors indicate no funding support. Contributions of authors: design and conduct of the study (C.T.H., N.H.F., K.S.D.); collection and management of data (C.T.H., N.H.F., K.S.D.); analysis and interpretation of data (C.T.H., K.S.D.); preparation of manuscript (C.T.H., K.S.D.); review and approval of manuscript (C.T.H., N.H.F., K.S.D.). The authors would like to acknowledge Roni M Shtein, MD, MS, University of Michigan Kellogg Eye Center, for her help with study design and manuscript review.
REFERENCES 1. Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984;28(4):293–322. 2. Pallikaris IG, Kymionis GD, Astyrakakis NI. Corneal ectasia induced by laser in situ keratomileusis. J Cataract Refract Surg 2001;27(11):1796–1802. 3. Negishi K, Kumanomido T, Utsumi Y, Tsubota K. Effect of higher-order aberrations on visual function in keratoconic eyes with a rigid gas permeable contact lens. Am J Ophthalmol 2007;144(6):924–929. 4. Jhanji V, Sharma N, Vajpayee RB. Management of keratoconus: current scenario. Br J Ophthalmol 2011;95(8):1044–1050. 5. Barnett M, Mannis MJ. Contact lenses in the management of keratoconus. Cornea 2011;30(12):1510–1516. 6. Lass JH, Lembach RG, Park SB, et al. Clinical management of keratoconus. A multicenter analysis. Ophthalmology 1990; 97(4):433–445. 7. Lembach RG. Use of contact lenses for management of keratoconus. Ophthalmol Clin North Am 2003;16(3):383–394. vi. 8. Wagner H, Barr JT, Zadnik K. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: methods and findings to date. Cont Lens Anterior Eye 2007;30(4):223–232. 9. Jensen LB, Hjortdal J, Ehlers N. Longterm follow-up of penetrating keratoplasty for keratoconus. Acta Ophthalmol 2010; 88(3):347–351. 10. Lim L, Pesudovs K, Coster DJ. Penetrating keratoplasty for keratoconus: visual outcome and success. Ophthalmology 2000;107(6):1125–1131. 11. Paglen PG, Fine M, Abbott RL, Webster RG Jr. The prognosis for keratoplasty in keratoconus. Ophthalmology 1982; 89(6):651–654. 12. Sayegh FN, Ehlers N, Farah I. Evaluation of penetrating keratoplasty in keratoconus. Nine years follow-up. Acta Ophthalmol (Copenh) 1988;66(4):400–403. 13. Zadok D, Schwarts S, Marcovich A, et al. Penetrating keratoplasty for keratoconus: long-term results. Cornea 2005;24(8): 959–961. 14. Tan DT, Dart JK, Holland EJ, Kinoshita S. Corneal transplantation. Lancet 2012;379(9827):1749–1761.
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15. Pramanik S, Musch DC, Sutphin JE, Farjo AA. Extended long-term outcomes of penetrating keratoplasty for keratoconus. Ophthalmology 2006;113(9):1633–1638. 16. Pecego M, Barnett M, Mannis MJ, Durbin-Johnson B. Jupiter Scleral Lenses: the UC Davis Eye Center experience. Eye Contact Lens 2012;38(3):179–182. 17. Gumus K, Gire A, Pflugfelder SC. The impact of the Boston ocular surface prosthesis on wavefront higher-order aberrations. Am J Ophthalmol 2011;151(4):682–690.e682. 18. Baran I, Bradley JA, Alipour F, Rosenthal P, Le HG, Jacobs DS. PROSE treatment of corneal ectasia. Cont Lens Anterior Eye 2012;35(5):222–227. 19. Schornack MM, Patel SV. Scleral lenses in the management of keratoconus. Eye Contact Lens 2010;36(1):39–44. 20. Lee JC, Chiu GB, Bach D, Bababeygy SR, Irvine J, Heur M. Functional and visual improvement with prosthetic replacement of the ocular surface ecosystem scleral lenses for irregular corneas. Cornea 2013;32(12):1540–1543. 21. Rathi VM, Mandathara PS, Dumpati S, Vaddavalli PK, Sangwan VS. Boston ocular surface prosthesis: an Indian experience. Indian J Ophthalmol 2011;59(4):279–281. 22. Alio JL, Shabayek MH. Corneal higher order aberrations: a method to grade keratoconus. J Refract Surg 2006;22(6): 539–545. 23. Krumeich JH, Daniel J, Knulle A. Live-epikeratophakia for keratoconus. J Cataract Refract Surg 1998;24(4):456–463. 24. Sabesan R, Johns L, Tomashevskaya O, Jacobs DS, Rosenthal P, Yoon G. Wavefront-guided scleral lens prosthetic device for keratoconus. Optom Vis Sci 2013;90(4):314–323. 25. Shepard DS, Razavi M, Stason WB, et al. Economic appraisal of the Boston Ocular Surface Prosthesis. Am J Ophthalmol 2009;148(6):860–868.e862. 26. Stason WB, Razavi M, Jacobs DS, et al. Clinical benefits of the Boston Ocular Surface Prosthesis. Am J Ophthalmol 2010;149(1):54–61. 27. Segal O, Barkana Y, Hourovitz D, et al. Scleral contact lenses may help where other modalities fail. Cornea 2003;22(4): 308–310. 28. Geerards AJ, Vreugdenhil W, Khazen A. Incidence of rigid gas-permeable contact lens wear after keratoplasty for keratoconus. Eye Contact Lens 2006;32(4):207–210.
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29. Silbiger JS, Cohen EJ, Laibson PR. The rate of visual recovery after penetrating keratoplasty for keratoconus. CLAO J 1996; 22(4):266–269. 30. Kim MH, Chung TY, Chung ES. A retrospective contralateral study comparing deep anterior lamellar keratoplasty with penetrating keratoplasty. Cornea 2013;32(4):385–389. 31. Chen M, Yoon G. Posterior corneal aberrations and their compensation effects on anterior corneal aberrations in keratoconic eyes. Invest Ophthalmol Vis Sci 2008;49(12): 5645–5652. 32. Price MO, Gorovoy M, Benetz BA, et al. Descemet’s stripping automated endothelial keratoplasty outcomes compared with penetrating keratoplasty from the Cornea Donor Study. Ophthalmology 2010;117(3):438–444.
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33. Pinero DP, Nieto JC, Lopez-Miguel A. Characterization of corneal structure in keratoconus. J Cataract Refract Surg 2012;38(12):2167–2183. 34. Reinhart WJ, Musch DC, Jacobs DS, Lee WB, Kaufman SC, Shtein RM. Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report by the American Academy of Ophthalmology. Ophthalmology 2011;118(1):209–218. 35. Zadnik K, Mannis MJ, Johnson CA, Rich D. Rapid contrast sensitivity assessment in keratoconus. Am J Optom Physiol Opt 1987;64(9):693–697. 36. Mendes F, Schaumberg DA, Navon S, et al. Assessment of visual function after corneal transplantation: the quality of life and psychometric assessment after corneal transplantation (Q-PACT) study. Am J Ophthalmol 2003;135(6): 785–793.
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Biosketch Karen S. DeLoss, OD is a graduate of Illinois College of Optometry, Chicago, IL. She completed a post-doctoral fellowship at the University of Houston, College of Optometry, Houston, TX and a clinical fellowship at Boston Foundation for Sight, Needham, MA. She is currently on faculty at the University of Michigan, Department of Ophthalmology, Kellogg Eye Center, Ann Arbor, Michigan.
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Biosketch Christopher T. Hood, MD is a Clinical Assistant Professor in Ophthalmology and Visual Sciences at the University of Michigan Kellogg Eye Center. Dr Hood received his medical degree from the University of Michigan, completed a residency in ophthalmology at the Cleveland Clinic Cole Eye Institute, and returned to the University of Michigan to complete a fellowship in cornea, external disease, and refractive surgery before joining the faculty. His research interests are clinical studies related to refractive surgery, the cornea, and cataracts.
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To compare the ocular characteristics and visual outcomes of eyes with corneal ectasia that were fitted with the Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) scleral device to those that underwent keratoplasty. DESIGN: Retrospective, comparative case series. METHODS: We reviewed the charts of consecutive patients with corneal ectasia that were evaluated for PROSE or underwent keratoplasty at our institution. Clinical data, topographic indices, and corneal thickness were reviewed, and eyes were stratified according to the Amsler-Krumeich classification for severity of ectasia. Only the more severe eye of each patient was included in the study. We compared visual acuity before and after PROSE fitting or keratoplasty. For PROSE evaluations, achievement of satisfactory fit and continued wear at 1 year of follow-up were recorded. RESULTS: From 2010 to 2012, 36 patients underwent PROSE evaluation for corneal ectasia while 37 patients underwent keratoplasty for the same indication. All eyes were successfully fitted with the PROSE device. Eyes in the keratoplasty group had more severe ectasia than eyes in the PROSE group (P [ .038). Visual acuity was achieved more rapidly in the PROSE cohort compared to keratoplasty, and mean visual acuity was significantly better for all eyes (P < .0001) and when including only eyes with stage 4 ectasia (P < .001). More eyes with stage 4 ectasia achieved 20/25 visual acuity after PROSE than after keratoplasty (P [ .003). At 1 year follow-up in the PROSE cohort, Snellen acuity was 20/28 (P [ .108 vs keratoplasty), improving to 20/25 with over-refraction (P [ .006 vs keratoplasty). CONCLUSIONS: Eyes with advanced corneal ectasia can be successfully fitted with the PROSE device, and the visual acuity outcome for stage 4 ectasia was better and more rapid compared to keratoplasty. The acuity remained excellent with 1 year of follow-up. PROSE Accepted for publication Jul 15, 2014. From the University of Michigan W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan. Nadeem H. Fatteh is currently at Kresge Eye Institute, Wayne State University, Detroit, Michigan. Inquiries to Christopher T. Hood, University of Michigan Kellogg Eye Center, 1000 Wall St, Ann Arbor, MI 48105; e-mail: hoodc@med. umich.edu
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evaluation should be considered in patients with advanced corneal ectasia before proceeding to keratoplasty, especially if the ectasia is deemed stable. (Am J Ophthalmol 2014;158:974–982. Ó 2014 by Elsevier Inc. All rights reserved.)
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ISUAL ACUITY IN CORNEAL ECTASIA, INCLUDING
keratoconus (KCN), pellucid marginal degeneration, and ectasia after laser in situ keratomileusis (LASIK), may be reduced because of both irregular astigmatism and corneal scarring,1–3 and management primarily consists of optical correction to maximize visual function.4 Although most patients with ectasia can be managed with spectacles and contact lenses,4–7 12%–20% of patients with keratoconus will progress to corneal transplantation because of difficulty achieving satisfactory vision or comfort with contact lenses.4,6,8 Although keratoplasty is often successful in increasing visual acuity,9–13 the potential exists for significant intraoperative and postoperative morbidity,14 especially given the expected survivorship of patients with KCN.15 Recently, large-diameter lenses that vault the cornea and limbus and rest on the sclera have emerged as a treatment option to improve the visual function of patients with severe corneal ectasia.5,16–20 The Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) is a customfitted device developed at the Boston Foundation for Sight (Needham, Massachusetts, USA) to restore vision, reduce symptoms, and improve quality of life for patients suffering from complex corneal disease including corneal ectasia. Other authors have previously described use of the PROSE device to improve visual function of patients with corneal ectasia whose vision is not adequately corrected with spectacles or other types of contact lenses,17,18,20,21 and it has been suggested that many of these patients may otherwise require corneal transplantation. However, no previous studies have evaluated the success of the PROSE device based on the severity of corneal ectasia, or directly compared PROSE patients to those who underwent corneal transplantation. Therefore, the purpose of the current study was to compare the demographics, ocular characteristics, and visual outcomes of consecutive eyes with corneal ectasia referred for PROSE evaluation at our institution to consecutive eyes with corneal ectasia that underwent keratoplasty during the same time period.
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RIGHTS RESERVED.
0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2014.07.016
MATERIALS AND METHODS THE UNIVERSITY OF MICHIGAN INSTITUTIONAL REVIEW
Board approved this retrospective study, which was conducted in accordance with the tenets of the Declaration of Helsinki guidelines and all applicable federal and state laws. We included consecutive eyes from January 2010 to December 2012 that were referred for PROSE evaluation for corneal ectasia, or that underwent keratoplasty for the same indication during the same time period, at the W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA. For the current study, corneal ectasia included a clinical diagnosis made by a fellowship-trained corneal specialist of KCN, pellucid marginal degeneration, or post-LASIK ectasia. All PROSE evaluations and fittings were completed by 1 provider (K.D.) who completed a PROSE clinical fellowship at the Boston Foundation for Sight. For each patient, only the eye with more severe ectasia was included in this study. Five surgeons performed the corneal transplants, with surgical technique varying according to surgeon preference; both penetrating keratoplasty (PKP) and deep anterior lamellar keratoplasty (DALK) were included. The decision to pursue PROSE evaluation or keratoplasty was at the surgeon’s discretion. From the medical records we recorded the corrected distance visual acuity (CDVA), including the method used to achieve the acuity, in the 3 months prior to PROSE evaluation or keratoplasty. We also recorded habitually corrected visual acuity (HCVA), defined as the visual acuity in correction that a patient utilized on a regular basis. This term was defined since some patients with corneal ectasia can refract better with spectacle correction but cannot tolerate the full prescription, or can achieve improved acuity with a contact lens but are unable to wear it because of comfort or fit. Topographic indices including average central keratometry, and simulated minimum and maximum keratometry as measured by Humphrey Atlas 993 corneal topographer (Carl Zeiss Meditec, Jena, Germany), Orbscan IIz (Bausch and Lomb, Rochester, New York, USA), or Pentacam HR (Oculus, Wetzlar, Germany) at the time of clinical evaluation, were recorded. Apical corneal thickness as assessed by ultrasound pachymetry (Pachette 2; DGH Technology Inc, Exton, Pennsylvania, USA), Orbscan IIz, or Pentacam HR, was also recorded. In order to assess the severity of corneal ectasia, we used the Amsler-Krumeich classification22,23 (Table 1), which uses the refraction, clinical findings on slit lamp examination, corneal curvature, and corneal thickness. For eyes that underwent successful PROSE fitting, we recorded the number of visits and the length of time needed to achieve a fit, as well as visual acuity after completion of the fitting process and at 1 year of follow-up. Assessment of continued wear was determined at the 1 year follow-up visit by patient-reported number of hours of average wear time
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TABLE 1. Amsler-Krumeich Classification for Staging Keratoconus Stage 1 Eccentric steepening Myopia, induced astigmatism, or both 55.00 D Central corneal scarring Minimum corneal thickness 200 mm D ¼ diopters. A single criterion is necessary for inclusion in a stage.
per day. Complications related to PROSE wear were recorded. For eyes in the keratoplasty group, complications as well as CDVA with method to achieve acuity at 3, 6, 9, and 12 months postoperatively were recorded. Comparisons between the demographics, ocular characteristics, and visual outcomes of both groups were made using 2-tailed t tests and Fisher exact test. Snellen acuity was converted to logarithm of the minimal angle of resolution (logMAR) for statistical analysis. All statistical analyses were performed with a Microsoft Office Excel statistical package (Redmond, Washington, USA) with a P value 60 diopters (D) (n ¼ 10), mean visual acuity was 20/25 after PROSE fitting. Figure 3 displays the percentage of all eyes, as well as stage 4 eyes only, that achieved 20/40 or 20/25 Snellen acuity. There were no significant differences in the percentage of eyes that attained 20/40 acuity between the PROSE and keratoplasty cohort. However, the PROSE group had a higher percentage of eyes with 20/25 acuity when considering all eyes, as well as those with stage 4 ectasia (P ¼ .001 and P ¼ .003, respectively). Figure 4 displays the visual acuity over time after PROSE evaluation or keratoplasty. After keratoplasty, mean acuity continued to improve until the 12-month follow-up visit. The mean spherical equivalent spectacle correction was 1.68 D 1 year after keratoplasty, with 3.04 D of refractive astigmatism; 10 patients (27%) required an RGP to achieve their best acuity. PROSE device fitting took 2.38 6 1.41 months and 6.49 6 2.13 visits, at which time best acuity was achieved. One year of follow-up was available for 34 patients fitted for PROSE; of those, 5 patients had discontinued device wear. Two discontinued wear because of unsatisfactory vision, 1 had difficulty inserting and removing the device, 1 had irregular sleeping habits that prevented device wear, and 1 had acute corneal hydrops. If the 2 patients who did not return for follow-up were assumed to have discontinued wearing PROSE, the success rate for continued wear at 1 year would be 80.6% (29/36). In the 29 patients that were still wearing PROSE at 1 year, the average wear time was 13.0 6 3.3 hours per day and the mean acuity was 20/28 (P ¼ .108 vs keratoplasty), improving to 20/25 with over-refraction (P ¼ .006 vs keratoplasty). Eight of 10 eyes with mean keratometry >60 D
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TABLE 3. Amsler-Krumeich Severity in the PROSE and Keratoplasty Cohorts PROSE (N ¼ 36)
Amsler-Krumeich stage, n (%) Stage 1 Stage 2 Stage 3 Stage 4
Keratoplasty (N ¼ 37)
P Value
.038 0 5 (13.9%) 6 (16.7%) 25 (69.4%)
0 0 4 (10.8%) 33 (89.2%)
PROSE ¼ Prosthetic Replacement of the Ocular Surface Ecosystem.
were wearing PROSE at 1 year; mean acuity was 20/35, improving to 20/30 with over-refraction. There were 1 intraoperative and 5 postoperative complications related to keratoplasty (16.2%). One patient had a partial expulsion of the crystalline lens secondary to a Valsalva maneuver. Postoperatively, a dense white cataract developed with vision limited to light perception, and the patient is scheduled to undergo cataract surgery. Three patients had episodes of graft rejection that resolved with frequent application of topical corticosteroids. One patient developed broad peripheral anterior synechiae and elevated intraocular pressure. Another patient developed a suture abscess that required application of cyanoacrylate glue for a microperforation. No complications of PROSE device wear were noted.
DISCUSSION IN THIS RETROSPECTIVE COMPARATIVE CASE SERIES ALL
candidate eyes with corneal ectasia could be successfully fitted with the PROSE device, regardless of corneal steepness, thinning, or presence of opacity. Visual outcomes for eyes with stage 4 ectasia, as graded by the AmslerKrumeich classification, were better and visual rehabilitation was more rapid after PROSE fitting compared to keratoplasty. With 1 year of follow-up, some patients discontinued wearing the PROSE device, and mean visual acuity declined slightly but still remained excellent. Our results suggest that even in cases of advanced ectasia, PROSE evaluation should be considered before keratoplasty, especially if the ectasia is deemed stable and unlikely to progress. Optical correction to increase visual functioning in patients with corneal ectasia needs to address myopia, irregular astigmatism, and corneal scarring.1–3 Scleral lenses are unique in that they vault the cornea to mask high amounts of astigmatism and rest on the less innervated sclera, providing better comfort. Among scleral lenses, PROSE is unique because each device is custom designed VOL. 158, NO. 5
FIGURE 1. Scatterplot of visual acuity of all eyes before and after PROSE fitting or keratoplasty. HCVA [ habitually corrected visual acuity.
by the fitter using proprietary computer-aided design and manufacturing software, employing spline functions, that is linked to a high-precision, high-resolution, computerized lathe. Additionally, PROSE incorporates wavefrontguided optics to correct higher-order aberrations, which may contribute to increased visual acuity tolerance and enhanced vision.24 The fitting process for the PROSE device has previously been described.25,26 Other authors have described the use of scleral lenses, including the PROSE device, for improvement in vision and function in patients with corneal ectasia,5,16,17,19,20,26 but no authors have quantified the severity of ectasia, compared outcomes to those after surgery, or presented long-term follow-up. Most eyes in our study had severe ectasia (stage 3 or 4) according to the Amsler-Krumeich classification, with more severity in the keratoplasty cohort compared to the PROSE cohort. Our results for visual outcomes compare favorably to other reported studies with the PROSE device, and, similarly to previous studies, we also report HCVA,20,26 since it more accurately characterizes the acuity that the patient utilizes on a daily basis. In our study, Snellen-equivalent visual acuity improved from worse than 20/200 at baseline to better than 20/25 after PROSE fitting; a similar improvement occurred when considering only eyes with stage 4 ectasia. In their recent series, Lee and associates reported an improvement from Snellen equivalent 20/94 to 20/24 in keratoconic patients fitted with PROSE,20 while Baran and associates reported an improvement from 20/73 to 20/25.18 Other authors have reported that 87%–93% of patients with keratoconus achieve 20/40 or better acuity with scleral lenses.18,19,27 In our study, 100% of eyes with stage 4 ectasia achieved 20/40 or better acuity, and 80% of eyes achieved 20/25 or better acuity. Comparing only eyes with stage 4 ectasia, mean visual acuity as well as percentage of eyes achieving 20/25 acuity was significantly better after PROSE fitting compared to keratoplasty. Additionally, owing to high and irregular astigmatism, 10 eyes (27%) needed an RGP after keratoplasty to achieve optimal acuity, consistent
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FIGURE 2. Mean visual acuity of all eyes (Top) and stage 4 eyes only (Bottom) at baseline and after PROSE fitting or keratoplasty. The standard error bars are displayed. CDVA [ corrected distance visual acuity (obtained in office); HCVA [ habitually corrected distance visual acuity; *P < .0001, **P < .001.
with previously published reports28,29; 6 discontinued RGP wear owing to lens intolerance. At 1 year, the majority of patients were still wearing PROSE with excellent acuity. However, some patients that initially achieved a satisfactory fit were no longer wearing the device and the mean acuity declined slightly. Acuity was still significantly better than keratoplasty if the power of the device was modified based on over-refraction. 978
A hypothetical advantage of scleral lenses is that fewer modifications of power should be needed with ectasia progression, since the cornea is completely vaulted by sterile saline; it is not entirely clear why power changes are necessary if the cornea remains vaulted, and further investigation in the area is warranted. Of note, 1 patient with mean keratometry >60 D underwent acute corneal hydrops, underscoring that fact that ectasia progression
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FIGURE 3. Percentage of eyes achieving 20/40 or better acuity (Top) or 20/25 or better acuity (Bottom) after PROSE fitting or keratoplasty.*P < .05, **P [ .001, ***P [ .003.
can still occur while wearing PROSE and suggesting that DALK should be considered in patients with advanced keratoconus deemed at risk for progression. This could avoid the need for a future PKP and the associated higher risk of graft rejection and endothelial cell loss.30 All eyes in our study that underwent PROSE evaluation had previously failed other methods of vision correction, yet all were successfully (when defined as objective and subjective improvement in visual acuity with a comfortable fit) VOL. 158, NO. 5
fitted with PROSE. Importantly, no eyes were excluded because of corneal thinning, opacity, or steepness. However, some patients still discontinued PROSE device wear. Baran and associates were also successful in fitting PROSE for all candidate eyes with ectasia, and reported continued device use in 88% of eyes.18 Lee and associates reported an 82% successful fitting rate. Interestingly, 2 patients in our series discontinued PROSE wear because of unsatisfactory vision, despite achievement of 20/20 acuity; 1 was the
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FIGURE 4. The rate of visual recovery after PROSE fitting or keratoplasty. For keratoplasty, acuity is displayed at standard postoperative visits. For PROSE, fitting took an average of 2.4 months, at which time best-corrected acuity with the device was achieved.
only patient in the PROSE cohort to have intrastromal corneal ring segments. It is possible that significant uncorrected higher-order aberrations from the posterior cornea led to dissatisfaction with vision,31 but this was not investigated in the current study. In our study, only 1 patient underwent PROSE evaluation but elected to proceed with keratoplasty, while 2 declined evaluation and 1 did not proceed owing to lack of insurance coverage, despite qualifying for financial assistance from the Boston Foundation for Sight. Of the remaining patients in the keratoplasty group, we suspect that a referral was not made because of axial corneal scarring that was presumed to limit visual acuity. However, many patients classified as stage 4 ectasia because of corneal scarring were able to achieve excellent visual acuity with PROSE, suggesting that neutralization of high and irregular astigmatism with the device mitigates the visual significance of some scarring and may delay or avoid the need for keratoplasty. CDVA was achieved more rapidly after PROSE fitting compared to keratoplasty. Our results are consistent with those of other authors that have reported that approximately 6 visits are needed to achieve successful PROSE treatment19,20; in our study, these visits occurred over approximately 2.5 months. Because of a paucity of PROSE providers nationwide, many patients fitted at our institution travel a significant distance, and travel planning sometimes determines the frequency of the fitting visits. CDVA after keratoplasty continued to improve until the 1-year time point, consistent with other published results.32 The potential for more rapid visual rehabilitation after PROSE fitting compared to keratoplasty has implications in the young, working patient population that often presents with ectasia. 980
No significant differences were observed in keratometric data between the PROSE and keratoplasty cohorts; however, we recognize the groups are likely not equivalent for a number of reasons. First, owing to variations in practice patterns between the corneal specialists, measurement with a tomographic device was not performed on many eyes that underwent keratoplasty, limiting the number of accurate measurements in this group and biasing the results toward less severe ectasia. Even with advanced tomographic devices, data were unobtainable for many eyes, given the severity of ectasia. We also recognize there is also an inherent bias in comparing 2 groups that are dictated by physician decision (ie, referral for PROSE vs keratoplasty). Acknowledging these limitations, we classified ectasia using a standard system to attempt to make comparison more appropriate. A limitation of the current classification system for corneal ectasia is that it does not stratify patients beyond stage 4, restricting the ability to discriminate amongst the most severe cases. To overcome this, we report the outcomes of eyes more severe than the current classification system (mean keratometry >60 D) that underwent PROSE fitting. For all eyes fitted for PROSE, high disease severity is reflected by an average mean simulated keratometry of 56.49 6 8.92 D. Although data from multiple devices were averaged for keratometry, the slight variability is likely not clinically significant in steep and irregular corneas.33 An additional reason to consider PROSE for patients with ectasia is the potential morbidity associated with keratoplasty, given the lengthy expected survivorship of these patients.15 Although the rate of a clear graft after penetrating keratoplasty for keratoconus is reported to be up to 89% at 10 years,14 there are numerous potential intraoperative and postoperative complications, including graft rejection, graft failure, glaucoma, suture-related infections, and open globe injury.14 There is no risk of endothelial immune rejection after DALK, but other unique complications exist, such as a postoperative Descemet membrane detachment and reduced acuity because of opacification at the interface.34 In our series, 16% of eyes (6/37) had a complication related to keratoplasty, 3 of which could be considered serious, with potential long-term sequelae. We did not encounter any complications related to PROSE wear. To our knowledge, there are no published reports on the rate of complications associated with PROSE wear, including bacterial keratitis, and this should be an area of further study. The main strength of our study is that we compared consecutive eyes with ectasia that underwent PROSE evaluation to those that underwent keratoplasty using a standardized classification system with 1 year of follow-up. We also included only 1 eye from each patient, assuring independence of our data points. We are limited, however, by our relatively small sample size and the retrospective nature of our study. Our assessment of visual acuity was Snellen acuity under standard clinic conditions, which does not assess high-contrast and low-contrast visual acuity that
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may be decreased in patients with ectasia.35 We did not compare visual results to those of other commercially available contact lenses. We did not objectively evaluate patient visual functioning or comfort, although others have demonstrated improved visual functioning of patients fitted with the PROSE device,26 as well as after keratoplasty.36 In summary, we demonstrate successful visual rehabilitation using the PROSE device in eyes with severe ectasia,
with better acuity and more rapid visual rehabilitation compared to eyes that underwent keratoplasty. Excellent acuity was maintained at 1 year in the PROSE cohort. Further prospective comparative clinical studies are warranted, but PROSE evaluation should be considered in contact lens–intolerant patients, especially those with stable ectasia, as surgery may be able to be delayed or even avoided.
ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST and none were reported. The authors indicate no funding support. Contributions of authors: design and conduct of the study (C.T.H., N.H.F., K.S.D.); collection and management of data (C.T.H., N.H.F., K.S.D.); analysis and interpretation of data (C.T.H., K.S.D.); preparation of manuscript (C.T.H., K.S.D.); review and approval of manuscript (C.T.H., N.H.F., K.S.D.). The authors would like to acknowledge Roni M Shtein, MD, MS, University of Michigan Kellogg Eye Center, for her help with study design and manuscript review.
REFERENCES 1. Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984;28(4):293–322. 2. Pallikaris IG, Kymionis GD, Astyrakakis NI. Corneal ectasia induced by laser in situ keratomileusis. J Cataract Refract Surg 2001;27(11):1796–1802. 3. Negishi K, Kumanomido T, Utsumi Y, Tsubota K. Effect of higher-order aberrations on visual function in keratoconic eyes with a rigid gas permeable contact lens. Am J Ophthalmol 2007;144(6):924–929. 4. Jhanji V, Sharma N, Vajpayee RB. Management of keratoconus: current scenario. Br J Ophthalmol 2011;95(8):1044–1050. 5. Barnett M, Mannis MJ. Contact lenses in the management of keratoconus. Cornea 2011;30(12):1510–1516. 6. Lass JH, Lembach RG, Park SB, et al. Clinical management of keratoconus. A multicenter analysis. Ophthalmology 1990; 97(4):433–445. 7. Lembach RG. Use of contact lenses for management of keratoconus. Ophthalmol Clin North Am 2003;16(3):383–394. vi. 8. Wagner H, Barr JT, Zadnik K. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: methods and findings to date. Cont Lens Anterior Eye 2007;30(4):223–232. 9. Jensen LB, Hjortdal J, Ehlers N. Longterm follow-up of penetrating keratoplasty for keratoconus. Acta Ophthalmol 2010; 88(3):347–351. 10. Lim L, Pesudovs K, Coster DJ. Penetrating keratoplasty for keratoconus: visual outcome and success. Ophthalmology 2000;107(6):1125–1131. 11. Paglen PG, Fine M, Abbott RL, Webster RG Jr. The prognosis for keratoplasty in keratoconus. Ophthalmology 1982; 89(6):651–654. 12. Sayegh FN, Ehlers N, Farah I. Evaluation of penetrating keratoplasty in keratoconus. Nine years follow-up. Acta Ophthalmol (Copenh) 1988;66(4):400–403. 13. Zadok D, Schwarts S, Marcovich A, et al. Penetrating keratoplasty for keratoconus: long-term results. Cornea 2005;24(8): 959–961. 14. Tan DT, Dart JK, Holland EJ, Kinoshita S. Corneal transplantation. Lancet 2012;379(9827):1749–1761.
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15. Pramanik S, Musch DC, Sutphin JE, Farjo AA. Extended long-term outcomes of penetrating keratoplasty for keratoconus. Ophthalmology 2006;113(9):1633–1638. 16. Pecego M, Barnett M, Mannis MJ, Durbin-Johnson B. Jupiter Scleral Lenses: the UC Davis Eye Center experience. Eye Contact Lens 2012;38(3):179–182. 17. Gumus K, Gire A, Pflugfelder SC. The impact of the Boston ocular surface prosthesis on wavefront higher-order aberrations. Am J Ophthalmol 2011;151(4):682–690.e682. 18. Baran I, Bradley JA, Alipour F, Rosenthal P, Le HG, Jacobs DS. PROSE treatment of corneal ectasia. Cont Lens Anterior Eye 2012;35(5):222–227. 19. Schornack MM, Patel SV. Scleral lenses in the management of keratoconus. Eye Contact Lens 2010;36(1):39–44. 20. Lee JC, Chiu GB, Bach D, Bababeygy SR, Irvine J, Heur M. Functional and visual improvement with prosthetic replacement of the ocular surface ecosystem scleral lenses for irregular corneas. Cornea 2013;32(12):1540–1543. 21. Rathi VM, Mandathara PS, Dumpati S, Vaddavalli PK, Sangwan VS. Boston ocular surface prosthesis: an Indian experience. Indian J Ophthalmol 2011;59(4):279–281. 22. Alio JL, Shabayek MH. Corneal higher order aberrations: a method to grade keratoconus. J Refract Surg 2006;22(6): 539–545. 23. Krumeich JH, Daniel J, Knulle A. Live-epikeratophakia for keratoconus. J Cataract Refract Surg 1998;24(4):456–463. 24. Sabesan R, Johns L, Tomashevskaya O, Jacobs DS, Rosenthal P, Yoon G. Wavefront-guided scleral lens prosthetic device for keratoconus. Optom Vis Sci 2013;90(4):314–323. 25. Shepard DS, Razavi M, Stason WB, et al. Economic appraisal of the Boston Ocular Surface Prosthesis. Am J Ophthalmol 2009;148(6):860–868.e862. 26. Stason WB, Razavi M, Jacobs DS, et al. Clinical benefits of the Boston Ocular Surface Prosthesis. Am J Ophthalmol 2010;149(1):54–61. 27. Segal O, Barkana Y, Hourovitz D, et al. Scleral contact lenses may help where other modalities fail. Cornea 2003;22(4): 308–310. 28. Geerards AJ, Vreugdenhil W, Khazen A. Incidence of rigid gas-permeable contact lens wear after keratoplasty for keratoconus. Eye Contact Lens 2006;32(4):207–210.
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29. Silbiger JS, Cohen EJ, Laibson PR. The rate of visual recovery after penetrating keratoplasty for keratoconus. CLAO J 1996; 22(4):266–269. 30. Kim MH, Chung TY, Chung ES. A retrospective contralateral study comparing deep anterior lamellar keratoplasty with penetrating keratoplasty. Cornea 2013;32(4):385–389. 31. Chen M, Yoon G. Posterior corneal aberrations and their compensation effects on anterior corneal aberrations in keratoconic eyes. Invest Ophthalmol Vis Sci 2008;49(12): 5645–5652. 32. Price MO, Gorovoy M, Benetz BA, et al. Descemet’s stripping automated endothelial keratoplasty outcomes compared with penetrating keratoplasty from the Cornea Donor Study. Ophthalmology 2010;117(3):438–444.
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33. Pinero DP, Nieto JC, Lopez-Miguel A. Characterization of corneal structure in keratoconus. J Cataract Refract Surg 2012;38(12):2167–2183. 34. Reinhart WJ, Musch DC, Jacobs DS, Lee WB, Kaufman SC, Shtein RM. Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report by the American Academy of Ophthalmology. Ophthalmology 2011;118(1):209–218. 35. Zadnik K, Mannis MJ, Johnson CA, Rich D. Rapid contrast sensitivity assessment in keratoconus. Am J Optom Physiol Opt 1987;64(9):693–697. 36. Mendes F, Schaumberg DA, Navon S, et al. Assessment of visual function after corneal transplantation: the quality of life and psychometric assessment after corneal transplantation (Q-PACT) study. Am J Ophthalmol 2003;135(6): 785–793.
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Biosketch Karen S. DeLoss, OD is a graduate of Illinois College of Optometry, Chicago, IL. She completed a post-doctoral fellowship at the University of Houston, College of Optometry, Houston, TX and a clinical fellowship at Boston Foundation for Sight, Needham, MA. She is currently on faculty at the University of Michigan, Department of Ophthalmology, Kellogg Eye Center, Ann Arbor, Michigan.
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Biosketch Christopher T. Hood, MD is a Clinical Assistant Professor in Ophthalmology and Visual Sciences at the University of Michigan Kellogg Eye Center. Dr Hood received his medical degree from the University of Michigan, completed a residency in ophthalmology at the Cleveland Clinic Cole Eye Institute, and returned to the University of Michigan to complete a fellowship in cornea, external disease, and refractive surgery before joining the faculty. His research interests are clinical studies related to refractive surgery, the cornea, and cataracts.
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