Steven J. Wiffen

The Effect of Contact Lens Wear on the Central and Peripheral Corneal Endothelium

PURPOSE To compare central and peripheral corneal endothelial cell morphometry in normal subjects and long-term contact lens wearers. METHODS Endothelial cell density (ECD), coefficient of variation of cell area (CV), and percentage of six-sided cells were measured by contact specular microscopy in the corneal center and temporal periphery of both eyes of 43 long-term contact lens wearers and in 84 normal subjects who had never worn contact lenses. The latter group included 43 age- and sex-matched controls for the contact lens wearers. ECDs were corrected for magnification changes due to corneal thickness. RESULTS Central ECD (2,723+/-366 cells/mm2, mean +/- SD) was significantly higher than peripheral ECD (2,646+/-394 cells/mm2) for the normal group (p = 0.01) but not for the contact lens wear group (2,855+/-428 cells/mm2 central, 2,844+/-494 cells/mm2 peripheral, p = 0.84). Peripheral CV was significantly higher than central for normal subjects and contact lens wearers and was significantly higher in both center and periphery in contact lens wearers than in controls. Central percentage of six-sided cells was significantly higher than peripheral for normal subjects and contact lens wearers and was lower in both center and periphery in contact lens wearers than in controls. CONCLUSIONS Central ECD was significantly higher by 3% than peripheral ECD in normal subjects, but not in contact lens wearers. The results suggest that contact lens wear causes a mild redistribution of endothelial cells from the central to the peripheral cornea. A reversal of this redistribution after contact lens wear is discontinued for refractive surgery could mask mild central endothelial damage from the refractive procedure.

Morphologic Assessment of Corneal Endothelium by Specular Microscopy in Evaluation of Donor Corneas for Transplantation

Our purpose was to evaluate the role of specular microscopy in the assessment of donor corneas for transplantation. We conducted retrospective analysis of specular microscopic evaluations of 1,000 consecutive donor corneas processed at Mayo Clinic Eye Bank from 1986 to 1993. Thirty-four of the 1,000 corneas were excluded from transplantation use on the basis of specular microscopic examination. Twenty-four corneas were excluded because of the presence of dark spots on the endothelium that did not clear with time. Large endothelial cells were found in six corneas on inspection, with a mean cell density of 1,160 cells/mm2 (795–1,597 cells/mm2). The remaining four excluded corneas showed evidence of endothelial trauma. Of 966 corneas not excluded, 520 (mean cell density 2,632 cells/mm2, range 1,621–4,590 cells/ mm2) were transplanted at the Mayo Clinic, and the rest were distributed for transplantation elsewhere, when possible. Six of the corneas transplanted at the Mayo Clinic (1.2%) failed primarily. There were no significant differences in the preoperative characteristics of the donor corneas between the donor failures and the clear grafts. Specular microscopic examination excluded 3.4% of donor corneas on the basis of unsatisfactory endothelium. Despite examination of the endothelium, six of 520 transplanted corneas (1.2%) suffered primary graft failure. Morphologic assessment of donor corneal endothelium by specular microscopy probably lessens, but does not eliminate, the risk of primary donor failure.

KERATOMETRIC RESULTS OF PENETRATING KERATOPLASTY WITH THE HESSBURG-BARRON AND HANNA TREPHINE SYSTEMS USING A STANDARD DOUBLE-RUNNING SUTURE TECHNIQUE

Purpose To compare final, sutures-out, keratometric results of penetrating keratoplasty using two different suction trephine systems and a standard double-running suture technique. Methods Keratometric data after final suture removal were compared retrospectively for three groups of transplants: Group 1. 7.50-mm Hessburg-Barron recipient trephine and 7.70-mm modified Lieberman donor punch (n = 70); Group 2. 7.50-mm Hessburg-Barron recipient trephine and 8.00-mm modified Lieberman donor punch (n = 18); Group 3, 7.50-mm Hanna recipient trephine and 7.75-mm Hanna donor punch (n = 68). Results Final average keratometry was 46.7±2.4 D (mean±SD, diopters), and final median keratometric astigmatism was 4.6 D (2.6–7.4 D, interquartile range), with no significant difference between groups. Final average keratometry values increased from preoperative values by 3.3±2.7 D. The correlation between preoperative average keratometry values and final values was low (rs = 0.2; p = 0.07). Average keratometry values increased by 2.3 D (median) after 10/ 0 suture removal (p < 0.0001) and by 0.2 D (median) after 11/0 suture removal (p = 0.09), with no significant difference between groups. There was a negative correlation between donor age and overall change in average keratometry (rs = −0.3;p = 0.002). Visual acuity improved by a median of 5 lines, with no significant difference between trephine systems. Conclusions There was no statistically significant difference in keratometric results using these two suction trephines with a standard suture technique. Final graft curvature was greater with both suction trephines compared with previously published results of transplants using hand-held trephines with the same suture technique.

Corneal graft rejection precipitated by uveitis secondary to alendronate sodium therapy.

Purpose: To report a case of corneal graft rejection precipitated by severe uveitis secondary to alendronate therapy and to review the literature of relevance to this case. Methods: A 77-year-old woman with a hypopyon and corneal graft rejection was studied for possible precipitants, including herpes viral and bacterial infection. Results were negative. She was treated unsuccessfully with systemic and topical steroids, systemic antivirals, and intraocular antibiotic therapy. Results: Withdrawal of alendronate resulted in rapid resolution of intraocular inflammation and corneal edema. Conclusion: We recommend vigilance in corneal transplant patients on simultaneous bisphosphonate therapy. Caution is advised in the extension to human trials of animal studies investigating the use of bisphosphonates in corneal transplantation.

Posterior Amorphous Corneal Dystrophy: A New Pedigree with Phenotypic Variation

BACKGROUND Posterior amorphous corneal dystrophy is a rare condition characterized by bilateral sheet-like opacification of the posterior stroma in association with corneal flattening and thinning. It has been reported in only four families, all from the United States. The authors report on a fifth family, the first from Britain, with nine affected individuals. METHODS Slit-lamp photography, refraction, keratometry, pachometry, corneal topography, and specular microscopy were used to assess the family members. RESULTS Two distinct forms of the disease were identified. All patients with the centroperipheral form were hypermetropic and had keratometry readings below 41.00 diopters and a central corneal thicknesses less than 0.50 mm. Those with the less severe peripheral form were less hypermetropic, some slightly myopic, and had keratometry readings above 41.00 diopters, but the central corneal thicknesses was similar to those with the centroperipheral form. No abnormalities of the endothelium were detected, and visual acuity was only mildly affected. The condition appears to be nonprogressive. CONCLUSION Though the centroperipheral form of posterior amorphous corneal dystrophy is more likely to lead to presentation, most patients are asymptomatic. This dystrophy can be very subtle in its appearance and easily overlooked. This led the authors to suspect that the prevalence of this condition is higher than the few reports in the ophthalmic literature suggest.

Lysosomal enzymes in corneal storage media and corneal graft outcome.

Purpose The purpose of this study was to relate lysosomal enzyme activities in corneal storage media to the outcome of the transplanted corneas. Methods Corneal storage media from 358 transplanted corneas were frozen at −70°C and kept for enzyme analysis. Corneas were stored in K-Sol (28), CSM (35), Dexsol (80), Index medium (five), Optisol (158), and Optisol GS (52). Activities of α-D-mannosidase, β-glucuronidase, α-glucosidase, and N-acetyl-β-glucosaminidase were assayed fluorometrically. Mayo Clinic records were examined for donor information, including cause of death and 2-month graft follow-up data. Results For all corneas, there was a low but significant correlation between activities of each enzyme and storage time (r-s = 0.13–0.35; p = 0.02–0.0001), and donor age (rs = −0.14 to −0.23; p = 0.009–0.0001). There was no significant correlation of enzyme activity with 2-month endothelial cell density, structure, cell loss, or corneal thickness. Enzyme activities for four primary donor failures and six grafts with <65% 2-month endothelial cell loss were not significantly different from those for the rest of the transplanted corneas. Enzyme activities were higher for corneas from donors with renal failure but not from those with diabetes mellitus. There was no significant difference in graft outcome for different cause-of-death groups. Conclusions The activities of lysosomal enzymes released into corneal storage media are not useful as predictors of graft outcome.

Specular microscopy before and after enucleation of live donor eyes

PURPOSE To compare the results of specular microscopic examination of corneal endothelium before and after enucleation of eyes from live donors. METHODS Endothelial cell density (ECD), coefficient of variation of cell area (CV), and percent hexagonal cells were compared for 34 cornea donors before enucleation of their eyes and after excision of the corneoscleral rims and placement in preservative media. RESULTS There was no statistically significant difference in ECD, CV, or percent six-sided cells after enucleation. The pre-enucleation and post-enucleation ECD measurements were significantly correlated (rs = .85, P < .0001). Mean percentage change in ECD was -0.7% +/- 6.0%. CONCLUSIONS There was no significant difference in ECD, CV, or percent six-sided cells between measurements taken from the epithelial side in vivo and those taken of the same corneas from the endothelial side in vitro after enucleation and corneoscleral rim excision. These findings suggest that it is reasonable to compare postkeratoplasty clinical measurements with those of the donor corneas taken in the eye bank.

Corneal Manifestations of Systemic Diseases

Accessible online at: www.karger.com/journals/oph The cornea may be affected directly or indirectly in many systemic diseases and by many different mechanisms leading to compromise of transparency, optical function or structural integrity. The cornea is derived embryologically from surface ectoderm and neural crest cells. Syndromes involving abnormal development of these cell layers, or of the structures around the developing eye, may affect the cornea. The ectodermal origin of corneal epithelium means that the cornea is frequently directly involved in diseases affecting the skin and mucous membranes as well as being secondarily affected by lid and conjunctival disease. Inherited disorders of metabolism of proteins, carbohydrates or lipids can lead to accumulation of substances, which may become evident as opacities in the corneal epithelium (e.g. Fabry’s disease), stroma (e.g. cystinosis) or Descemet’s membrane (e.g. Wilson’s disease). Some disorders of protein formation may cause structural abnormalities of the cornea. Corneal deposits or opacities can also occur in acquired conditions, such as crystals in multiple myeloma and deposits in the corneal epithelium associated with the use of many drugs. Corneal nerves are abnormal in several conditions affecting peripheral nerves in general. Infective or immune-mediated keratitis may occur as localized involvement in a systemic process or as extension of disease from contiguous sclera or conjunctiva. Secondary corneal involvement can occur in any disease affecting the surrounding structures, including conjunctiva, lids, lacrimal system and tear film. Ophthalmologists should be aware of corneal abnormalities that suggest the presence of an underlying systemic disease and of the corneal manifestations of systemic disease that may require specific therapy.