Ernesto E. Blanco

Radial keratotomy does not affect intraocular pressure.

BACKGROUND Recent reports have suggested that a secondary effect of radial keratotomy may be a reduction in intraocular pressure (IOP) levels. METHODS In an effort to study the relationship of radial keratotomy to IOP, we compared the mean IOP from the baseline and follow-up visits during 1 year after surgery of operated versus nonoperated eyes of patients enrolled in the Prospective Evaluation of Radial Keratotomy (PERK) study. To investigate if radial keratotomy had more of an effect on eyes with higher baseline IOPs, the same analysis was performed on a subset (134 patients) who had a baseline IOP of 15 mm Hg or greater. RESULTS The average baseline IOP for both operated eyes and nonoperated eyes was 14.6 mm Hg. There was no significant difference in mean IOP between operated and nonoperated eyes across all time points (p = .18). Although mean IOP changed over time, it did not clinically differ in operated versus nonoperated eyes at any time point. These findings were similar in the analysis of eyes with higher baseline IOP (15 mm Hg or greater). CONCLUSION We conclude that the radial keratotomy performed in the PERK study had no effect on IOP within 1 year after surgery.

Evaluation of Increased Aqueous Outflow After Radial Keratotomy in Enucleated Bovine Eyes

PURPOSE We studied the efficacy of using radial keratotomy incisions as a surgical method of increasing outflow facility in enucleated bovine eyes. METHODS Each freshly enucleated bovine eye (n = 23) was cannulated to a system measuring the rate of flow into the eyes. Preoperatively, corneal thickness measurements were determined for all treated eyes. Radial keratotomy was performed in 13 eyes and a control set of eyes (n = 10) had no surgical manipulation. The intraocular pressure was set at 16.9 mm Hg. A clear zone of 10 mm was used for each eye with the incision depth set at 100% of the pachymetric reading. One set of experimental eyes had incisions that remained in the clear cornea, and the other set had incisions that reached 2 mm beyond the limbus into sclera. Preoperative outflow measurements were performed on each eye. Postoperative measurements were made after 10 incisions and 20 incisions. All eyes were checked for perforation after surgery and discarded if a perforation was found. RESULTS No eye included in the analysis was perforated. The preoperative (baseline) total flow rate was 27.90 +/- 3.72 mu 1/min at 16.9 mmHg. The flow rate increased by 23.5% (over baseline) with 20 radial keratotomy incisions. A paired t-test was used to statistically compare the outflow measurements before radial keratotomy and after the first and second set of radial incisions. The increases in flow were found to be statistically significant (P < .005) for both 10 and 20 radial incisions. CONCLUSION Assuming the flow measurements (flow rate) in these experiments parallel outflow facility, radial keratotomy increases the outflow facility in enucleated bovine eyes.