The potential for eye bank limbal rings to generate cultured corneal epithelial allografts.

PURPOSE: Patients with severe limbal deficiencies are unable to maintain a stable corneal surface. If sheets of cultured allogeneic corneal epithelium could be prepared from eye banked corneal limbal rings, which are normally discarded after keratoplasty, the sheets may be beneficial for grafting onto patients with limbal stem cell deficiencies. METHOD: Biopsies of limbal tissue (2-3 mm2) removed from organ-cultured corneal limbal rings or from fresh whole globes were either trypsinized or set up as explants to assess their potential for corneal epithelial cell production. RESULTS: Several biopsies were taken from each of 21 organ-cultured limbal rings and 10 fresh cadaveric globes. Cultures were generated from every cadaveric eye (10/10), although not all biopsies from the same eye gave rise to cultures. Confluent sheets of cultured cells were also produced successfully from limbal rings that had been in organ culture for up to 25 days, but the success rate from limbal ring material was variable (14/21). An analysis of parameters associated with each limbal ring was carried out in an attempt to identify the reasons for the different efficiencies of epithelial production. No obvious single parameter correlation was detected, although there was a trend to poorer efficiency with increased donor age. CONCLUSIONS: Confluent sheets of cultured corneal epithelial cells, suitable for grafting, can be produced from limbal tissue taken from eye bank organ-cultured corneas, although it takes longer, on average, to reach confluence (17-21 days) than an equivalent sample from a fresh eye (9-12 days).

Hyperopic photorefractive keratectomy with the erodible mask and axicon system: two year follow-up.

PURPOSE: To evaluate efficacy and long-term stability of hyperopic photorefractive keratectomy (H-PRK) using the erodible mask and Axicon system. SETTING: Department of Ophthalmology, St. Thomas' Hospital, London, England. METHODS: Forty-three patients (43 eyes), with a mean preoperative refraction (spherical equivalent) of +4.54 diopters (D) (range +1.75 to +7.50 D), were treated using an Apex Plus(R) excimer laser (Summit Technology). This uses an erodible mask to ablate a 6. 50 mm diameter hyperopic correction and an Axicon to fashion a 1.50 mm blend zone around the correction. The overall ablation diameter was 9.50 mm. Follow-up was 2 years. RESULTS: At 2 years, the mean manifest refraction was +0.16 D (range +4.125 to -4.000 D), with the induced correction appearing stable after 9 months. Based on the Munnerlyn algorithm, predictability was acceptable for corrections up to +4.50 D, with 68% of eyes within +/-1.00 D of the predicted correction. It was poorer for +6.00 D corrections, with 33% of eyes within +/-1.00 D of that expected. Patient satisfaction was high. Forty eyes (93%) had an improvement in uncorrected near visual acuity and 37 (86%), an improvement in uncorrected distance acuity. A peripheral ring of haze, 6.5 mm in diameter, appeared in all eyes 1 month postoperatively. Its intensity was maximal at 3 to 9 months and then diminished over time. There were no significant differences in measurements of the central corneal transparency at 12 and 24 months and those preoperatively. Measurements of flicker contrast sensitivity, forward light scatter (glare), and scotopic halos showed no significant differences between preoperative values and those measured after 6 months. CONCLUSIONS: Achieved H-PRK corrections with the erodible mask and Axicon system agreed closely with the Munnerlyn algorithm, with refractive stability after 9 months. Predictability was acceptable for corrections up to +4.50 D. Axial corneal transparency was not compromised and visual performance, in terms of best spectacle-corrected visual acuity, forward light scatter, and night halos, was not impaired.