Frozen cultured sheets of epidermal keratinocytes in reepithelialization and repair of the cornea after photorefractive keratectomy

PURPOSE

To determine whether frozen cultured sheets of human allogeneic epidermal keratinocytes (CEAK) improved wound repair after experimental corneal ablation by photorefractive keratectomy (PRK).

SETTING

Hospital "Luis Sanchez Bulnes" de la Asociación para Evitar la Ceguera en Mexico, I.A.P, and Department of Cell Biology, CINVESTAV-IPN, Mexico City, Mexico.

METHODS

Transepithelial PRK was performed in the right eye of male albino rabbits to obtain a 112 microm deep and 6.0 mm diameter ablation zone. In 17 eyes, the ablations were covered with frozen CEAK; in 11 eyes, the ablations were covered with a disposable contact lens without the cultured sheets; and in the control group (13 eyes), the ablations were not covered. Subepithelial fibrosis and reepithelialization of the ablated zone were evaluated in serial paraffin-embedded tissue sections from all wounds.

RESULTS

Treatment with CEAK reduced fibroblast proliferation and the inflammatory response beneath the ablated zone and produced better organization of the newly formed epithelium by eliminating significant hyperplasia or discontinuities in the periodic acid Shiff-stained basement membrane. It also led to accelerated reepithelialization.

CONCLUSIONS

The use of frozen CEAK as a biologically active wound dressing improved tissue repair at 1 month in corneas ablated by transepithelial PRK in the male albino rabbit model. Treatment with CEAK could improve the outcome of PRK in humans.

Epithelial removal with the excimer laser (laser-scrape) in photorefractive keratectomy retreatment

OBJECTIVES

To retrospectively evaluate refractive and topographic outcomes after excimer laser photorefractive keratectomy (PRK) retreatment using the laser-scrape technique for epithelial removal.

DESIGN

Retrospective clinical study.

PARTICIPANTS

Thirty eyes of patients who had PRK retreatment for undercorrection after primary PRK were examined.

INTERVENTION

The PRK retreatment was performed using a laser-scrape technique in which the excimer laser was used to remove the majority of the epithelium overlying the anterior stromal surface before additional PRK ablation.

MAIN OUTCOME MEASURES

Uncorrected visual acuity, best-corrected visual acuity (BCVA), surface regularity index (SRI), and surface asymmetry index were measured.

RESULTS

Primary PRK was performed for myopia of -5.1 +/- 1.7 diopters (range, -1.1 to -7.5 diopters). Mean spherical equivalent (SE) was -1.3 +/- 0.4 diopters (range, -0.6 to -2.0 diopters) before retreatment. Mean SE 6 months after retreatment decreased to +0.1 +/- 0.4 diopter (range, +1.25 to -0.75 diopters; P < 0.0001). Four eyes (15%) were more than +0.5 diopter overcorrected at 6 months. Ninety-six percent of eyes achieved mean SE within +/- 1 diopter and 77% within +/- 0.5 diopter of emmetropia after retreatment. Visual acuity improved significantly 6 months after reablation (P < 0.0001) with 100% 20/40 or better and 73% 20/25 or better without correction. Final BCVA also improved compared with before retreatment (P = 0.02). Twelve eyes gained 1 line of BCVA and no eye lost more than 1 line of BCVA. The SRI before retreatment was 0.6 +/- 0.3 (range, 0.0-0.9) and remained the same 0.6 +/- 0.2 (range, 0.1-1.0; P = 0.8), 6 months after retreatment.

CONCLUSION

Excimer laser PRK retreatment using the laser-scrape technique for epithelial removal is an accurate and safe procedure for treating undercorrection of eyes after PRK for low-to-moderate myopia.

Retreatment of Regression after Photorefractive Keratectomy for Myopia

PURPOSE

To study results of retreatment after regression in myopic patients who underwent photorefractive keratectomy (PRK).

METHODS

Procedures were performed with the Nidek EC-5000 excimer laser. This was a retrospective study of 20 of 2127 patients, with follow-up of at least 6 months, who underwent repeated excimer laser ablation.

RESULTS

No patient with low myopia had regression. We evaluated six eyes (group I) with moderate myopia; 13 eyes (group II) with high myopia; and ten eyes (group III) with extreme myopia. Average uncorrected visual acuity at 6 months after retreatment was 0.73 +/- 0.21 in group I, 0.64 +/- 0.35 in group II, and 0.61 +/- 0.38 in group III. At six months after retreatment, the average was -0.36 +/- 1.05 D in group I, -0.42 +/- 1.12 D in group II, and -1.40 +/- 1.62 D in group III.

CONCLUSION

The amount and frequency of regression was higher in patients with high and extreme myopia; however, the preliminary results of retreatment of regression were satisfactory.