Changes of contrast visual acuity under photopic environment following excimer laser corneal refractive surgery

Objective To investigate the changes of contrast visual acuity (CVA) under photopic environment in patients with low/moderate myopias treated by femtosecond laser-assisted in situ keratomileusis (FS-LASIK) versus laser assisted subepithelial keratomileusis (LASEK). Methods The FS-LASIK group and the LASEK group consisted of 20 right eyes (20 patients) respectively.The spherical equivalent ranged from -1.00 to -5.00 D. The patients were tested with multi-functional visual acuity tester-100(MFVA-100) at 4 contrast levels (100%, 25%, 10%, 5%) before operation and at 1 week, 1 month, 3 months after operation. Results As for the FS-LASIK group, 5% CVA at 1 week after operation was significantly lower than that before operation under photopic environment (0.473±0.230) vs (0.291±0.088), P< 0.05, but the levels at 1 month and 3 months after operation showed no statistically significant difference compared with the preoperative (0.290±0.095) and (0.271±0.115) vs (0.291±0.088), P> 0.05, and there was no statistically significant difference in 100%, 25%, 10% CVA before and after operation at different time points (P> 0.05). As for the LASEK group, CVA at each constrast level at 1 week after operation decreased compared with before operation (P < 0.05), 5% CVA at 1 month after operation did not returned to the preoperative level (0.589±0.224) vs(0.405±0.118), P< 0.05, and there was no statistically significant difference in 5% CVA before and at 3 months after operation(P> 0.05). Conclusion In mild-to-moderate myopic patients underwent excimer laser corneal refractive surgery, low contrast visual acuity (LCVA) decreases obviously in the early postoperative period. The CVAs of FS-LASIK group and LASEK group return to the preoperative level at 3 months after surgery. 5% CVA can be used as an evaluating indicator of postoperative visual quality.