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Michael S. Hughes Perry Rosenthal, M.D. President & Founder, Boston Foundation for Sight

Endothelial Cell Density As A Predictor Of Ocular Surface Prosthesis Design In The Visual Rehabilitation Of Penetrating Keratoplasty. World Cornea Congress VI April 7-9, 2010 Boston, MA. Michael S. Hughes Perry Rosenthal, M.D. President & Founder, Boston Foundation for Sight

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Michael S. Hughes Perry Rosenthal, M.D. President & Founder, Boston Foundation for Sight

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  1. Endothelial Cell Density As A Predictor Of Ocular Surface Prosthesis Design In The Visual Rehabilitation Of Penetrating Keratoplasty World Cornea Congress VI April 7-9, 2010 Boston, MA Michael S. Hughes Perry Rosenthal, M.D. President & Founder, Boston Foundation for Sight Assistant Clinical Professor of Ophthalmology, Harvard Medical School Trisha Hussoin, B.S./B.A. Deborah S. Jacobs, M.D. Medical Director, Boston Foundation for Sight Assistant Clinical Professor of Ophthalmology, Harvard Medical School Faculty, Mass. Eye & Ear Infirmary Cornea Service PR, TH, and DSJ are salaried, full-time employees of the Boston Foundation for Sight, a 501(c)(3) non-profit organization. The authors have no proprietary or financial interest in the Boston Ocular Surface Prosthesis (BOS-P).

  2. Abstract: Purpose: To evaluate endothelial cell density as a predictor of the need for fenestration in an ocular surface prosthesis in visual rehabilitation of PK. Methods: A retrospective case review of 96 eyes was performed in 68 consecutive patients seen at this center wearing an ocular surface prosthesis after PK. Fenestrations are used for report of colored haloes associated with micro-cystic epithelial edema. Age, sex, indication for PK, years of graft survival, pseudo-phakia, central pachymetry, endothelial cell density, pre/post-fit BCVA, and fenestration were recorded. Results: M:F = 37:31 with age 25-89 years. Graft survival range 0.08-40 yrs (mdn=9.4 yrs). 39.6% were pseudo- or aphakic. 75.0% were fitted with fluid-ventilated design; 25.0% required fenestration. Pachymetry in 82/96 eyes was 391.8-700.2 μm, not predictive of fenestration. Endothelial cell densities were 286-3392 cells/mm2. Decreased endothelial cell density (p=0.034) and increased years of graft survival (p=0.007) correlated with need for fenestration. Fitting success rate, ΔBCVA, and wearing status at 6 months are reported. Conclusion: Endothelial cell density and years of graft survival correlate with need for fenestration in an ocular surface prosthesis in visual rehabilitation of PK. Further study of use of fenestration to improve device tolerance is warranted.

  3. Introduction: Boston Ocular Surface Prosthesis (BOS-P) • RGP scleral lens (high Dkfluoro-silicone acrylate) • Diameter 17.5 – 23.0 mm • FDA approved in 1994 for treatment of corneal disorders • Irregular Astigmatism • Ocular Surface Disease • Custom designed using spline-based CAD/CAM software

  4. Introduction: Boston Ocular Surface Prosthesis (BOS-P) The BOS-P does not touch the cornea! ( a “non-contact” lens) Critical design features of the BOS-P • Vaults the cornea • Vault is independent of base curve • Bearing haptic • Defined by spline function • NOT super-position of spheres • Can be made toric • No movement on the eye • Fluid-ventilated Tear reservoir unmasked with fluorescein

  5. Introduction: Fenestration in scleral lens design • Fenestration (a small hole to allow air under the lens) 1 • Historically incorporated into PMMA scleral lenses • Meets metabolic needs of the cornea • Prevent lens suction • Gas permeable polymers eliminated need 2 • Poor endothelial function can limit RGP scleral lens wear • Symptomatic as “haloes” • Correlates with inter-epithelial cell edema • Fenestrated BOS-P developed for • Visual rehabilitation of failing grafts in high-risk eyes 1. Pullum K, Whiting M, Buckley R: Cornea 24:269-77, 2005. 2. Rosenthal P, Croteau A: Eye & Contact Lens 31:130-134, 2005. Fenestrated scleral lens Non-fenestrated scleral lens (Standard BOS-P)

  6. Fenestrated BOS-P:The first case • 62 y.o. M with Pellucid Marginal Degeneration • OD PK # 1 1973, corneal RGP, then scleral, graft failure PK # 2 2002, 8D of K cyl • OS PK # 1 1983, corneal RGP then scleral, 6D of K cyl In standard BOS-P In standard BOS-P 20/25, pach 0.540 20/30 “haloes”, pach 0.738 • Solution: FENESTRATION • 20/25 “no more haloes” • 16 h/d wear! • Fenestrated BOS-P can delay surgery in high-risk keratoplasty

  7. Methods: • Retrospective case review • 68 consecutive patients (96 eyes) • Seen at Boston Foundation for Sight, Needham, MA between 7/25/08 - 8/1/09 • History of penetrating keratoplasty • Fitted with or wearing an ocular surface prosthesis (BOS-P) • For visual rehabilitation • For support of ocular surface • Fenestrations were added for report of haloes associated with epithelial edema • Data extracted from medical records • Sex • Age • Indication for penetrating keratoplasty • Years of graft survival • Phakia • This study was determined to be exempt from review by New England IRB • Central pachymetry • Endothelial cell density • Visual acuity: pre-BOSP and post-BOS-P • Fenestration in prosthesis • Fitting success rate

  8. Results: Patient and Eye Characteristics • M:F = 37:31 • Age: 25-89 years • Phakic : pseudophakic : aphakic = 58 : 33 : 5 (eyes) • Standard BOS-P : Fenestrated BOS-P = 71 : 24 (eyes) (74.7% Standard)

  9. Results: Design of BOS-P by Years of Graft Survival nstandard = 72 eyes nfenestrated = 19 eyes • Years of graft survival: 0.08-40 years (median = 9.4 years) • Mean years of graft survival for eyes with standard lens: 9.8 • Mean years of graft survival for eyes with fenestrated lens: 18.1 • There is a significant difference between these means (p < 0.005; t-test)

  10. Results: Design of BOS-P by Endothelial Cell Density nstandard = 68 eyes nfenestrated = 23 eyes • Endothelial cell densities: 286-3392 cells/mm2 • Mean endothelial cell density of eyes with standard lenses = 1282.49 cells/mm2 • Mean endothelial cell density of eyes with fenestrated lenses = 986.09 cells/mm2 • There is a significant difference between these means (p < 0.05) • Pachymetry (82/96 eyes): 391.8-700.2 μm • There is no difference between the pachymetries in the eyes with standard lenses and the eyes with fenestrated lenses (p = -0.28)

  11. Results: Design of BOS-P by Visual Acuity nstandard = 57 eyes nfenestrated = 24 eyes

  12. Conclusions: BOS-P design for eyes s/p PK • Pachymetry does not correlate with need for fenestration • Lower endothelial cell density correlates with need for fenestration • Increased years of graft survival correlates with need for fenestration • Discussion • Possible mechanisms by which fenestration reduces epithelial edema include: • Support of metabolic demands of the cornea • via access to atmospheric oxygen • via increased tear exchange • Reduction of mechanical suction • There is no specific “cut-off” at which need for fenestration is absolute (suggesting that other factors are contributory) Bruce A, Brennan N: SurvOphthalmol 35:25-58, 1990. Chauhan A, Radke C: Optom Vis Sci 78:732-43, 2001. Rosenthal P, Jacobs D, Johns L: Contemporary Ophthalmol 5:1-7, 2006. Vannas A, Holden B, Sweeney D: Br J Ophthalmol 71:593-7, 1987

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