Endothelial Cell Density As A Predictor Of Ocular Surface Prosthesis Design In The Visual Rehabilitation Of Penetrating Keratoplasty

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).

World Cornea Congress VIApril 7-9, 2010Boston, MA

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.

Abstract:

RGP scleral lens (high Dk fluoro-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

Introduction:

Boston Ocular Surface Prosthesis (BOS-P)

The BOS-P does not touch the cornea! ( a “non-contact” lens)

Tear reservoir unmasked with fluorescein

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

Introduction:

Boston Ocular Surface Prosthesis (BOS-P)

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)

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

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

In standard BOS-P In standard BOS-P

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

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)

Results:

Patient and Eye Characteristics

29

1211

76 6

01

01

53 3

42

0 01

0

5

10

15

20

25

30

35

0-4.9 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45

Num

ber o

f Gra

fted

Eye

s

Years of Graft Survival

Design of BOS-P

Non-Fenestrated Lenses

Fenestrated Lenses

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)

nstandard = 72 eyes

nfenestrated = 19 eyes

Results:

Design of BOS-P by Years of Graft Survival

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)

nstandard = 68 eyes

nfenestrated = 23 eyes

Results:

Design of BOS-P by Endothelial Cell Density

nstandard = 57 eyes

nfenestrated = 24 eyes

Results:

Design of BOS-P by Visual Acuity

Conclusions:

BOS-P design for eyes s/p PK