Contrast sensitivity after excimer laser photorefractive keratectomy for myopia
AIM: To evaluate contrast sensitivity in patients who had undergone uncomplicated excimer laser photorefractive keratectomy (PRK) for myopia. METHODS: Monocular contrast sensitivity function was measured with the CSV-I000E chart in 41 patients who had received PRK by the Nidek EC-5000 excimer laser system. Mean preoperative refractive error was -2.62 +/- 1.33 D (range, -0.75 to -4.00 D). Contrast sensitivity function was measured preoperatively, 1week, 1, 3 and 6 months after surgery through the CSV-1000E contrast sensitivity unit (VectorVision). RESULTS: Logarithmic values of contrast sensitivity at each spatial frequency were used for statistical analysis and normalized values were used for graphical representation. Contrast sensitivity decreased 1 week and 1 month postoperatively. Starting from the first month, there was rapid recovery of contrast sensitivity especially at low spatial frequencies, and at the third month, only at 6 and 12 cycles per degree (cpd) statistically significant decrease was seen. Six months after surgery, there was an increase in contrast sensitivity values at all spatial frequencies. CONCLUSION: Photorefractive keratectomy can induce significant reductions in contrast sensitivity in the first month after surgery; these values returned to the preopereative values at 6 months after surgery.