Effect of photorefractive keratectomy for myopia on measurement of retinal nerve fiber layer thickness using optical coherence tomography

PURPOSE: To evaluate the effect of excimer laser photorefractive keratectomy (PRK) on nerve fiber layer thickness measurements by optical coherence tomography in myopic eyes. METHODS: Twenty-two patients who had PRK for myopia underwent nerve fiber layer measurement by optical coherence tomography in both eyes before and 6 months after surgery in the first operated eye and before surgery in the fellow (control) eye, 6 months after the first PRK. Optical coherence tomography was performed with a Humphrey Optical Coherence Tomography Scanner. Each eye was scanned at the nerve head program radius of 1.5. For each of the optical coherence tomography parameters (average for each quadrant, superior, inferior, temporal, nasal; average for each clock hour; average over the entire cylindrical section), descriptive statistics were calculated. The difference between the observed change from the first to the second examination was calculated between the treated and the control eye. Individual mean differences were tested with Student's t-test. Hotelling's T-squared generalized means test was used to determine whether the set of mean differences was equal to zero. RESULTS: The average preoperative refractive error was -3.90 +/- 1.50 D in treated eyes and -3.89 +/- 1.50 D in control eyes (P = .81, Student's t-test). Mean achieved refractive correction was 3.70 +/- 1.70 D, corresponding to. 48.1 +/- 22.1 mum of corneal ablation. No statistically significant difference was found in any measurement in the treated eye compared with the untreated control eye. CONCLUSIONS: At 6 months postoperatively, photorefractive keratectomy for moderate myopia that resulted in clear corneas did not affect nerve fiber layer thickness measurements, as obtained by optical coherence tomography.