Objective assessment of transient corneal haze and its relation to visual performance after photorefractive keratectomy

PURPOSE: Photorefractive keratectomy has the potential to cause transient c orneal haze. The purpose of this study was to evaluate the relationship bet ween transient corneal haze as measured by an objective means and high and low contrast visual performance. METHODS: In a prospective study, 44 eyes of 28 patients were examined preop eratively and at 1, 3, 6, and 12 months after photorefractive keratectomy. Five laser in situ keratomileusis and two intrastromal corneal ring segment s (Intacs [KeraVision, Fremont, CAI) were included for comparison, because these procedures are not expected to cause haze. Haze was measured using a prototype objective hazemeter, TSPC-3, a modification of the Nidek EAS-1000 . Visual performance was measured using high-contrast visual acuity and the Rabin Small Letter Contrast Test. RESULTS: Corneal haze was greatest at the 1-month examination and was consi stent with a decrease in visual performance on both tests. Corneal haze res olved in 82% of eyes by 10 +/- 4 months after photorefractive keratectomy. However, visual performance had not returned to preoperative levels in 65% and 81% of these eyes on the high,contrast visual acuity test and the Small Letter Contrast Test, respectively. Eyes that underwent laser in situ kera tomileusis and Intacs did not develop corneal haze; however, Visual decreme nts were measured. CONCLUSIONS: As a clinical tool, the TSPC-3 hazemeter objectively measures very subtle changes in haze levels. Corneal haze appears to account for onl y approximately 50% of visual performance changes in the early healing peri od after photorefractive keratectomy. Other factors, namely topographic abn ormalities, are more likely to be an important cause of persistent visual d isturbances. (C) 2001 by Elsevier Science Inc. All rights reserved.