Accommodative changes after photorefractive keratectomy in myopic eyes.

PURPOSE: To determine the changes of amplitude of accommodation (AA) and facility of accommodation (FA) in myopic patients after photorefractive keratectomy (PRK). METHODS: Using Technolas 217Z excimer laser, 160 myopic eyes of 80 patients underwent PRK. The patients were categorized into two age groups: <30 and ≥30 years. Changes in AA and FA were observed before PRK and at 2 weeks, 1 month, and 3 months after PRK. The role of preoperative AA, FA, refractive spherical equivalent, age, and sex on postoperative AA and FA was evaluated. RESULTS: In younger patients, the preoperative AA and FA values 7.77 ± 1.75 D and 7.75 ± 3.97 cpm changed to 8.36 ± 1.26 D and 11.57 ± 4.20 cpm (p < 0.001), respectively, at 3 months after PRK. In older patients, the preoperative AA and FA values 6.66 ± 1.41 D and 5.05 ± 3.26 cpm changed to 6.72 ± 1.26 D (p = 1.000) and 9.58 ± 4.29 cpm (p < 0.001), respectively. Two weeks after surgery, preoperative AA and spherical equivalent had a significant effect on postoperative AA, whereas preoperative AA and age had a significant effect on postoperative AA after 3 months (p < 0.001). Postoperative FA was positively related to preoperative FA and female sex (p < 0.05). CONCLUSIONS: This study suggests that some of the near-vision problems in younger myopes in early postoperative days after PRK might be due to decrease in AA and FA, which will eventually increase. However, in older patients, despite increase in FA, AA did not change.

Peripapillary retinal nerve fiber layer thickness measurement by three-dimensional optical coherence tomography in a normal population.

PURPOSE: To determine peripapillary retinal nerve fiber layer (RNFL) thickness values by three-dimensional optical coherence tomography (3D-OCT) in a normal Iranian population and to evaluate the concordance of these measurements with those obtained by the second generation of optical coherence tomography (OCT II). METHODS: In a cross-sectional observational study, 96 normal Iranian subjects 20-53 years old were enrolled. Peripapillary RNFL thickness in one randomly selected eye of each subject was measured by 3D-OCT and also by OCT II. Standard achromatic perimetry, corneal pachymetry and A-scan ultrasonographic biometry were also performed. Other study variables included age, gender, laterality (right versus left eye), refractive error, corneal diameter and disc area. RESULTS: Mean peripapillary RNFL thickness measured by 3D-OCT (75.50±8.38) µm was significantly less than that measured by OCT II (144.10±33.32 µm) (P<0.001). Using 3DOCT, no significant difference in peripapillary RNFL thickness was observed by gender (P=0.90) or laterality (P=0.17); RNFL thickness had no correlation with age (P=0.95), axial length (P=0.32), spherical equivalent refractive error (P=0.21), central corneal thickness (P=0.66) and disc area (P=0.31). However, a positive correlation was found between peripapillary RNFL thickness and corneal diameter (P=0.03). CONCLUSION: 3D-OCT seems to yield lower RNFL thickness values as compared to OCT II. It seems advisable to obtain separate baseline measurements when using different generations of OCT machines.