Causes of Best Corrected Visual Acuity Loss after Excimer Laser Photorefractive Keratectomy

Lim, Byoung Kak; Tchah, Hung Won

Abstract

Excimer laser photorefractive keratectomy(PRK) has been used as a good treatment modality for myopia. However many surgeon reported its complications, especially loss of best corrected visual acuity(BCVA) after PRK with an incidence of 0~12%. Thus we studied the causes and incidence of BCVA loss in myopic eyes that were followed up at least 12 months after PRK. We defined `BCVA loss` as 2 or more lines decrease by Snellen chart comparing to preoperative visual acuity. We found that 16 of 313 eyes(5.1%) lost BCVA during follow up period after PRK. High myopes, 8.25diopters or more, developed BCVA loss(8.8%) more commonly than myopes below 8.00 diopters(3.3%) (P<0.05). But BCVA loss recovered after post-operative 2 years except one eye. The causes of BCVA loss were corneal haze, irregular astigmatism, incidental cataract and steroid-induced glaucoma. According to the corneal haze scoring, average corneal haze was greater in eyes(1.47 score) with BCVA loss than eyes(0.36) without BCVA loss (P<0.01). However average cornea haze score in eyes with BCVA loss gradually decreased with time.As a result, main causes of BCVA loss after PRK was corneal haze, irregular astigmatism. High myopia more than 8.25 diopters showed greater BCVA loss than myopia less than 8.00diopters after PRK, but BCVA loss recovered with time.