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The preliminary results of hyperopic photorefractive keratectomy (HPRK) performed with the VISX-Star excimer laser on 40 eyes of 25 patients are presented. 28 of 40 eyes had vision of 20/40 at 6 months and 22 of 25 eyes saw 20/40 12 months postoperatively. Eleven of 40 patients were over corrected 1.00 D at 6 months and no patients were overcorrected with the same amount at 12 months postop. At six months, no undercorrections of 1.00 D were observed and 3 of 25 eyes were undercorrected by 1.00 D at 12 months postop. At 6 months postop, 35 of 40 eyes saw for near J5 or better, and 20 of 25 saw J5 at 12 months postop. Complications included: induced astigmatism of 1.00 D (6 of 40 eyes at 6 months and 3 of 25 eyes at 12 months), and loss of two lines of best corrected vision (4 of 40 at 6 month,s and 2 of 25 at 12 months). HPRK appears to be safe and effective in correcting hyperopia of up to 4.00 D in the short to medium term.

Preliminary results of the correction of myopia up to -7.00 D by tracked photorefractive keratectomy (T-PRK) with a scanning and tracking excimer laser by Autonomous Technologies are discussed. 41 eyes participated (20 males). 28 eyes were evaluated one month postop. At epithelization day mean uncorrected vision was 20/45.3. At one month postop, 92.8 of eyes were 20/40 and 46.4% were 20/20. No eye was worse than 20/50. 75% of eyes were within +/- 0.5 D of emmetropia and 82% were within +/- 1.00 D of emmetropia. Eyes corrected for monovision were included. One eye lost 3 lines of best corrected vision, and had more than 1.00 D induced astigmatism due to a central corneal ulcer. Additional complications included symptomatic recurrent corneal erosions which were controlled with topical hypertonic saline. T-PRK appears to allow effective correction of low to moderate myopia. Further study will establish safety and efficacy of the procedure.

Multivariable regression analysis was used to evaluate the combined effects of some preoperative and operative variables on the change of refraction following excimer laser photorefractive keratectomy for myopia (PRK). This analysis was performed on 152 eyes (at 6 months postoperatively) and 156 eyes (at 12 months postoperatively). The following variables were considered: intended refractive correction, patient age, treatment zone, central corneal thickness, average corneal curvature, and intraocular pressure. At 6 months after surgery, the cumulative R2 was 0.43 with 0.38 attributed to the intended correction and 0.06 attributed to the preoperative corneal curvature. At 12 months, the cumulative R2 was 0.37 where 0.33 was attributed to the intended correction, 0.02 to the preoperative corneal curvature, and 0.01 to both preoperative corneal thickness and to the patient age. Further model augmentation is necessary to account for the remaining variability and the behavior of the residuals.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy (PRK) on 240 eyes of 161 patients. With constant laser emission parameters, nitrogen (N2) flow across the cornea was used on 79 eyes while 161 eyes had no N2 flow. 74 eyes were operated on without fixation with a suction ring. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical Diclofenac or Ketorolac, and a therapeutic soft contact lens in 163 eyes. Follow up ranged from 1 month (206 eyes) to 36 months (10 eyes).© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Our two year experience with excimer laser photorefractive keratectomy for the correction of myopia on 160 eyes of 128 patients is described. All eyes were treated with a VISX Twenty- Twenty excimer laser, with the following parameters: radiant exposure 160 mJ/cm2, frequency 5 Hz, ablation zone diameter 5.0 to 5.5 mm, and stromal ablation rate 0.18 to 0.33 (mu) /pulse. A suction fixation ring was used in all cases either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from one month (152 eyes) to 24 months (12 eyes). The results are stable between 3 and 24 months with less than 0.25 D change in the mean postoperative spherical equivalents. In eyes with a follow-up of 6 to 24 months, 77% to 100% were 20/40 or better uncorrected, and 84% to 92% were corrected to within +/- 1 D of emmetropia. Further follow-up is needed to assess the long term safety and efficacy of the procedure.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.