Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK): Safety and Clinical Outcome for the Correction of Mild to Moderate Myopia with a Thin Cornea

PURPOSE: To evaluate the safety, clinical outcome, and change in higher-order wavefront aberrations (HOAs) of Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK) for the correction of mild to moderate myopia in cases with a thin cornea. METHODS: ASA-PRK was performed, using a rotary epithelial scrubber, post-laser chilled BSS(R) irrigation, and bandage contact lens, in 127 eyes of 70 patients who had a preoperative spherical equivalent within -7.0 D and who were followed-up for more than six months. The patients were divided into two groups, according to their central corneal thickness (CCT), by ultrasonic pachymetry (Group: CCT520 micrometer, 95 eyes, mean 552.3+/-24.8 micrometer). The clinical outcomes of Group I and II were compared. RESULTS: At six months, 100% of Group I (32/32 eyes) and 93.7% of Group II (89/95 eyes) had an UCVA of 1.0 or better (p>0.05). At six months, a spherical equivalent within 0.5 D of emmetropia was observed in 100% (32/32) of the eyes in Group I and in 94.7% (90/95) of the eyes in Group II (p>0.05). At the 12-month follow-up, all eyes showed good stability of the refractive errors, and none showed corneal haze of grade 1 or more, loss of two or more lines of BSCVA, or serious iatrogenic keratectasia. The magnitude of total HOAs, spherical ablation, and coma were significantly higher six and 12 months after surgery in both groups (p0.05). CONCLUSIONS: ASA-PRK performed on patients with mild to moderate myopia and a thin cornea (> or =490 micrometer) showed a high level of efficacy, predictability, stability, and safety. There was no statistically significant difference in surgically induced HOAs between Groups I and II. The authors suggest that ASA-PRK be used for the correction of mild to moderate myopia, especially in cases with a thin cornea. Further study will be needed to determine the safety of this procedure for thinner corneas in surface keratorefractive surgery.

Clinical Outcome of PRK with the Use of a Rotary Brush, Corneal Chilling, and Bandage Contact Lens

PURPOSE: To evaluate the effect of rotary epithelial scrubber, cold BSS(R) irrigation, and bandage contact lens on the clinical outcome of excimer laser PRK. METHODS: This updated PRK was performed in 90 eyes (Group I: -4.54 +/- 0.91 D). Conventional PRK with mechanical epithelial removal using Beaver(R) blade and patch dressing was performed in 181 eyes (Group II: -4.30 +/- 0.97 D). Clinical outcome was compared between group I and group II retrospectively. RESULTS: Mean epithelial removal time was significantly shorter in group I (6.6 +/- 0.9 sec) than in group II (33.2 +/- 11.2 sec) (p<0.05). Mean epithelial healing time showed more rapid epithelial healing in group I (2.0 +/- 0.3 days) than in group II (3.0 +/- 1.0 days) (p<0.05). At 1 week and 24 months, UCVA of 0.7 or better was achieved in 91.1%, 97.8% in group I and in 71.8%, 88.2% in group II (p<0.05). At 6 and 24 months, spherical equivalent within 0.5 D of emmetropia was in 91.1%, 91.3% in group I and in 80.7%, 56.9% in group II (p<0.05). After 1 year follow-up, no eye in group I showed either corneal haze worse than grade 1 or loss of 2 or more lines of BSCVA. CONCLUSIONS: Updated PRK provided more rapid epithelialization than conventional PRK. And there was significant improvement in clinical outcome and safety in group I compared with group II. We suggested that updated PRK should be used for the correction of mild to moderate myopia.

The Effect of Anterior Chamber Irrigation with OcuLarsol(R) on the Corneal Endothelial Cells

PURPOSE: To verify the stability and effect of OcuLarsol(R), which was newly developed for irrigating solution, by evaluating influence on cornea. METHODS: In vivo study group, after an irrigation and aspiration instrument was put into rabbit's anterior chamber: one eye was irrigated with OcuLarsol(R) for 15 minutes, and the other eye with the balanced salt solution (BSS(R), Alcon, USA). After the operation, corneal changes were observed for a week. In vitro study group, after enucleating of rabbits' eyeballs, corneas were mounted in a dual chambered specular microscope and perfused with glutathione bicarbonate Ringer's solution (GBR) for one hour: one cornea of the pair was perfused with OcuLarsol(R) and the other cornea was perfused with BSS(R) for 2-3 hours. After perfusion, corneal swelling rates and endothelial permeability were measured. RESULTS: In vivo study group, central corneal thickness measurement and endothelial cell count showed that there was no significant difference between the two groups on the day of operation, and 1st, 3rd and 7th day after the operation (p>0.05). Corneal endothelial observation with Alizarin red S, HandE stain, and scanning electron microscope detected no difference in cell shape and density. In vitro study group, corneal swelling rates and endothelial permeability showed no significant difference between OcuLarsol(R) and BSS(R) group and transmission electron microscope showed endothelial cells with normal organelles in all groups. CONCLUSIONS: There was no significant difference between the two irrigating solutions, BSS(R) and OcuLarsol(R), in terms of effect and side effects.