Central photorefractive keratectomy for myopia. Partially sighted and normally sighted eyes.

Ten partially sighted and 19 normally sighted eyes underwent excimer laser photorefractive keratectomy for the correction of myopia. Nine of the partially sighted and 17 of the normally sighted eyes had 12 months of follow-up. Epithelial healing was complete in all eyes by day 6. None of the eyes had recurrent erosions, infections, or other medical complications. An increase in corneal haze after surgery was followed by a slow trend toward clearing. Average uncorrected visual acuity in the 7 normally sighted eyes with attempted corrections of 5 diopters (D) or less was 20/40 from month 2 on; the eyes with greater than 5 D attempted corrections had an average of 20/80--at month 2, which declined to 20/200--by month 6. Best spectacle-corrected visual acuity was within +/- 1 Snellen line of preoperative values in 14 of the normally sighted eyes, improved 2 or more lines in 2 eyes, and worsened two or more lines in two eyes. Hard contact lens overcorrection restored all of the two-line loss in 1 eye and 1 line of the 3-line loss in the other. Refraction and keratometry indicated corneal flattening without induced astigmatism.

Myopic excimer laser photorefractive keratectomy: an analysis of clinical correlations.

In this study, we examined the correlations among various factors that may affect the results of central photorefractive keratectomy for myopia. Data analyzed from our studies of blind, partially sighted, and normally sighted eyes included patient age, attempted correction, time to re-epithelialization, postoperative corneal clarity, refraction (relative spherical equivalent), and uncorrected visual acuity. We found that larger attempted corrections resulted in less accurate refractions and poorer uncorrected visual acuity. Older patients tended to have better results than younger patients, regardless of the amount of attempted correction. The relationship between the amount of attempted correction and corneal clarity was weak. There was a statistical correlation between corneal clarity scores and uncorrected visual acuity, but the range of corneal clarity scores was small and even the highest scores were probably not in the range that interfered with vision, so the relationship was probably not causal. The rate of epithelial healing did not appear to affect either refractive or visual results, and was not affected by patient age. These findings may be useful in guiding future efforts to improve the results of this new surgical procedure for the correction of refractive error.

Evaluation of an opacity lensometer for determining corneal clarity following excimer laser photoablation.

The appearance of haze in the central cornea following photoablation with a 193 nm excimer laser is an important factor in the postoperative course of this procedure. Data from 37 human eyes treated with photorefractive keratectomy, 4 eyes treated with phototherapeutic keratectomy, and 5 untreated eyes were used to evaluate the ability of a commercially available opacity lensometer to provide an objective measure of corneal clarity. We found that the opacity lensometer was able to detect light scattered from the cornea but was not sufficiently sensitive to distinguish reliably among excimer-treated eyes with degrees of corneal haze evaluated as clear, trace, or 1+ by slit-lamp microscope examination. In untreated, clear corneas, the values obtained with the opacity lensometer in eyes measured with and without a clear contact lens were within one unit of each other for any given eye, but values from eye to eye varied over a range of six units. In a test simulating different amounts of corneal haze using contact lenses evenly coated with nail polish enamel, the log-transformed opacity lensometer values varied directly with percent light scattering as determined by spectrophotometry. These results suggest that the opacity lensometer measurements are reliable and reproducible, but that in the human cornea something is being measured by the opacity lensometer that is not taken into account in clinical slit-lamp microscope evaluation. Overall, it appears that, in its present form, this instrument is not useful to measure corneal clarity after excimer laser photoablation.