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Purpose: To evaluate the thinnest corneal thickness changes during and after corneal collagen cross-linking treatment with ultraviolet-A irradiation, using hypo-osmolar riboflavin solution in thin corneas., Methods: Eighteen eyes of 18 patients were included in this study. After epithelium removal, iso-osmolar 0.1% riboflavin solution was instilled to the cornea every 3 minutes for 30 minutes. Hypo-osmolar 0.1% riboflavin solution was then applied every 20 seconds for 5 minutes or until the thinnest corneal thickness reached 400 µm. Ultraviolet-A irradiation was performed for 30 minutes. During irradiation, iso-osmolar 0.1% riboflavin drops were applied every 5 minutes. Ultrasound pachymetry was performed at approximately the thinnest point of the cornea preoperatively, after epithelial removal, after iso-osmolar riboflavin instillation, after hypo-osmolar riboflavin instillation, after ultraviolet-A irradiation, and at 1, 6 and 12 months after treatment., Results: Mean preoperative thinnest corneal thickness was 380 ± 11 µm. After epithelial removal it decreased to 341 ± 11 µm, and after 30 minutes of iso-osmolar 0.1% riboflavin drops, to 330 ± 7.6 µm. After hypo-osmolar 0.1% riboflavin drops, mean thinnest corneal thickness increased to 418 ± 11 µm. After UVA irradiation, it was 384 ± 10 µm. At 1, 6 and 12 months after treatment, it was 372 ± 10 µm, 381 ± 12.7, and 379 ± 15 µm, respectively. No intraoperative, early postoperative, or late postoperative complications were noted., Conclusions: Hypo-osmolar 0.1% riboflavin solution seems to be effective for swelling thin corneas. The swelling effect is transient and short acting. Corneal thickness should be monitored throughout the procedure. Larger sample sizes and longer follow-up are required in order to make meaningful conclusions regarding safety.

Purpose: To evaluate the efficacy and safety of mitomycin C (MMC) 0.02% in inhibiting haze formation after excimer laser photorefractive keratectomy (PRK) for residual myopia following radial keratotomy (RK)., Methods: A prospective, nonrandomized, noncomparative interventional case series was conducted of 22 eyes (14 patients) with residual myopia after RK performed at a single institution. All eyes were treated with PRK and a single intraoperative topical application of MMC 0.02% solution for 2 minutes using a soaked cellulose sponge placed over the ablated area. Refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and slit-lamp evidence of cotneal opacity (haze) were evaluated over 12 months., Results: Twelve months postoperatively, 3 eyes showed grade 1 haze, and 2 eyes showed grade 0.5 haze. Twelve months postoperatively, 2 (9%) eyes had UCVA > or = 20/20. No eye before and 17 (77%) eyes after treatment had UCVA > or = 20/40, and no eye before and 9 eyes (40.9%) after treatment had UCVA > or = 20/25. Best spectacle-corrected visual acuity was > or = 20/40 in all (100%) eyes and 21 (95%) eyes before and after treatment, respectively, and > or = 20/25 in 12 (54.5%) eyes before and after treatment. One (4.5%) eye lost 1 line of BSCVA. Mean spherical equivalent refraction achieved was -0.18 diopters (D) (range: -0.75 to +0.50 D) compared to -2.72 D (range: -1.50 to -4.00 D) before treatment. Twelve months after treatment, 19 (85.5%) eyes had a refractive outcome within +/- 0.50 D., Conclusions: A single intraoperative application of MMC 0.02% for 2 minutes appears to be effective in preventing subepithelial haze after PRK for residual myopia in patients with undercorrection or regression following RK.

Purpose: To evaluate and compare the effect of hinge position and flap thickness on recovery rate of corneal sensation after (LASIK)., Design: Prospective, randomized clinical study., Methods: Forty eyes of 40 patients underwent LASIK to correct myopia ranging from -1.00 to -2.50 diopters. Corneal sensitivity was measured preoperatively and each month after surgery until recovery to preoperative level. The nasal-hinged ACS microkeratome (NH) with depth plates of 130 and 160 microm and the superior-hinged Hansatome microkeratome (SH) with depth plates of 160 and 180 microm were used for corneal flap creation. The eyes were divided into four groups according to the hinge position and depth plate (DP): group 1, NH and 130 microm DP; group 2, NH and 160 microm DP; group 3, SH and 160 microm DP; group 4, SH and 180 microm DP., Results: Corneal sensitivity returned to preoperative level after 3.7 (+/- 0.4), 4.4 (+/- 0.6), 5.4 (+/- 0.8), and 5.8 (+/- 0.9) months, respectively, in groups 1, 2, 3, and 4. Statistically significant differences were found between groups 1 and 2, but not between groups 3 and 4. Corneal sensitivity gradually returned to preoperative levels in all groups. Sensitivity of the hinge area was higher than other areas at every time point., Conclusions: The results suggest that after LASIK, hinge position and flap thickness seem to be important factors in the rate of return of corneal sensitivity. A thin flap with a nasally placed hinge is associated with the most rapid recovery of corneal sensitivity.

Objective: To evaluate the changes in corneal sensitivity after LASIK for the correction of different degrees of myopia., Design: Prospective, nonrandomized, comparative self-controlled trial., Participants: One hundred two myopic eyes of 58 patients were included in this study., Methods: The eyes were divided into four groups: group 1, from -0.75 to -3.75 diopters (D); group 2, from -4.00 to -7.75 D; group 3, from -8.00 to -11.75 D; group 4, from -12.00 to -16.00 D. Corneal sensitivity was measured before and 1, 7, 30, 90, 180, 270, and 365 days after surgery or until full recovery., Main Outcome Measures: The recovery of corneal sensation after LASIK., Results: Immediately after surgery, the lenticule was found to be completely anesthetic, and the full recovery varied according to the depth of the ablation. Normal levels of corneal sensitivity, but not full recovery, were found after 90 days in groups 1 and 2 and after 180 days in groups 3 and 4. Full recovery of corneal sensitivity was found after 180 days in groups 1 and 2 and after 270 days in groups 3 and 4., Conclusions: After LASIK, corneal sensitivity is decreased at the central and paracentral areas for as long as 9 months. The depth of the ablation seems to be an important factor in the temporary decrease of corneal sensitivity and its recovery.

Background: The capability of the 193-nm excimer laser to ablate the cornea and to remove opacities and various other corneal diseases in a procedure called phototherapeutic keratectomy (PTK) has been demonstrated. In this study we evaluated the long-term results of PTK for treatment of granular and lattice corneal dystrophies., Methods: Four eyes with granular or lattice corneal dystrophy were treated with a mean follow-up of 47.8 months (range, 36 to 58 months). Focal ablations of the central cornea with an ablation zone of 5.5 to 6.0 mm were performed. Ablation depth was 110 microns in three eyes and 140 microns in one eye., Results: Removal of corneal opacities allowed for improvement in corrected visual acuity in all patients. Mean corneal thickness in the area of pathology decreased from 0.583 mm before surgery to 0.449 mm after surgery. Spherical equivalent of the manifest refraction measurements increased by a mean of +5.09 D. There were no major complications, but all patients developed slight haze. There was a hyperopic shift in three eyes., Conclusion: Our long-term results suggest that PTK is a safe and effective alternative to penetrating and lamellar keratoplasty in patients with granular or lattice corneal dystrophies.

Background: To develop an in vitro model to study the effects of excimer laser keratectomy on corneal stromal cells, we evaluated two types of collagen gel populated with keratocytes., Methods: Keratocyte-populated collagen gels were prepared with type I collagen in 6-well plates or in culture plate inserts, the bottom of which consisted of a nitrocellulose membrane, contained within 6-well plates. The gels were ablated by the 193-nm excimer laser, set to ablate 50, 100, or 200 microns deep, and was observed under a phase-contrast microscope for 2 days., Results: Keratocytes cultured in collagen gel developed cytoplasmic processes and formed networks of interconnected cells. Cells within the ablated area in the 6-well plates began to lose their cytoplasmic processes and became round approximately 3 hours after excimer laser ablation. These cellular changes were more prominent in the gels ablated to a depth of 200 microns. Cells outside of the ablation zones in the 6-well plates and the culture plate inserts remained intact., Conclusions: These results suggest the use of keratocyte-populated collagen gel as an in vitro model of cellular response to excimer laser keratectomy and also suggest that gel prepared in culture plate inserts is the preferred method.

Purpose: To determine if keratocyte loss, after removal of the corneal epithelium, can be prevented by a collagen shield used alone or in combination with a topically applied corneal preservation medium., Methods: Twenty-four New Zealand white rabbits were divided into six groups of four rabbits each. The central 6 mm of corneal epithelium was removed from one eye of each animal by means of a blunt spatula. Postoperatively, these eyes were treated every 4 hours for 24 hours with the following: group 1, balanced salt solution (BSS) drops (Akorn Inc, Metairie, La); group 2, Optisol drops (Chiron IntraOptics, Irvine, Calif); group 3, a collagen shield soaked in sterile BSS plus BSS drops; group 4, the same collagen shield soaked in Optisol plus Optisol drops; group 5, a different collagen shield soaked in sterile BSS plus BSS drops; and group 6, the same collagen shield soaked in Optisol plus Optisol drops. The animals were killed at 24 hours after surgery, the corneas were fixed, and keratocytes within the anterior and posterior cornea, beneath the epithelial defect, were quantitated. Four untreated rabbits served as controls., Results: Optisol drops alone, applied every 4 hours after deepithelialization, did not prevent keratocyte loss to a greater extent than did BSS drops alone (P = .96). Both collagen shields soaked in sterile BSS plus BSS drops every 4 hours were associated with less keratocyte loss than were BSS or Optisol drops alone. Both collagen shields soaked in Optisol plus Optisol drops every 4 hours were most successful at minimizing keratocyte loss (P = .0002 and P = .001)., Conclusion: After corneal deepithelialization, use of a collagen shield in combination with topical application of a corneal storage medium may minimize keratocyte loss and may thus be beneficial after refractive surgery.

Purpose: To evaluate the ability of topical diclofenac to decrease corneal opacity after excimer laser photorefractive keratectomy (PRK)., Methods: Twenty New Zealand white rabbits underwent a unilateral 193-nm excimer laser myopic photorefractive keratectomy to correct 5 diopters. There were four groups of five rabbits each. The first group of rabbits received postoperative topical treatment with placebo (Voltaren Ophthalmic vehicle), the second group received topical 0.1% diclofenac, the third group received topical corticosteroid (0.1% fluorometholone), and the fourth group received diclofenac and fluorometholone. In the first month, the topical drugs were applied four times daily, and in the second month twice daily. Corneal haze was graded from 0 (totally clear) to 4 (completely opaque cornea). Slit-lamp pictures were obtained at weeks 2, 4, and 8, and keratometry readings was performed at weeks 4 and 8. At week 8, the rabbits were killed, and the eyes were submitted for histologic examination., Results: At week 8, there was less corneal haze in the diclofenac-treated animals and in the fluorometholone-treated animals than in the control group, but only in the diclofenac-treated group was the difference statistically significant. Combination treatment with diclofenac and fluorometholone did not result in a further decrease in haze., Conclusions: These data suggest that diclofenac and fluorometholone may influence corneal wound healing in rabbits after excimer laser PRK and support a potential role for using topical nonsteroidal anti-inflammatory drugs in preventing the development of excessive corneal haze after excimer laser surgery.

Purpose: Mini-radial keratotomy (mini-RK) involves limiting the extent of radial incisions to within 3.5 mm from the center of the central clear zone, compared with incisions that extend close to or beyond the limbus, as with "conventional" RK. This study was designed to determine if shorter incision length reduces the likelihood of corneal rupture after blunt trauma., Method: Sixteen fresh human anterior segments were divided into four groups and mounted onto an artificial anterior chamber. Four corneas with no incisions were used as controls, four received regular four-incision RK, four received four mini-RK incisions, and four received eight mini-RK incisions. Incisions extended from the 3.0-mm central clear zone to 1 mm inside the limbus (regular RK), or from the 3.0-mm central clear zone to the 7.0-mm mark (mini-RK). A pump slowly infused the artificial anterior chamber with a balanced salt solution while the pressure was continuously monitored with an electronic pressure transducer. The maximum pressure and the site of the rupture were recorded., Results: Control corneas ruptured at the limbus, whereas all surgical eyes ruptured at incision sites. The corneas subjected to mini-RK ruptured at significantly higher pressures than corneas that had undergone regular RK (P < 0.01)., Conclusion: Reducing incision length appears to reduce the likelihood of corneal rupture as intraocular pressure is increased. Mini-RK may be advantageous for patients at high risk for ocular trauma.