Corneal haze after photorefractive keratectomy for myopia - Role of collagen IV mRNA typing as predictor of haze

Purpose: To develop a test based on the individual expression of collagen type IV synthesis in corneal epithelial cells to identify patients who have the potential for significant corneal haze after myopic photorefractive keratectomy (PRK). Setting: Department of Ophthalmology and the Institute of Microbiology, University of Regensburg, Germany. Methods: The individual synthesis of collagen type IV alpha3 mRNA was quantitatively measured in corneal epithelial cells of 34 eye (34 patients) with myopia ranging from -1.5 to -10.0 diopters (D) by a polymerase chain reaction (PCR) test. The corneal epithelial cells were collected before the PRK procedure. Collagen type IV alpha3 mRNA levels were correlated to postoperative haze and regression at 12 months. Results: In all samples, collagen type IV alpha3 mRNA was detected; the mean was 1.47 (range 0.11 to 6.42). There was a correlation between haze and the amount of collagen type IV alpha3 mRNA; that is, eyes with haze had more collagen IV expression. In contrast, no correlation was observed between regression and the amount of collagen type IV alpha3 mRNA. Conclusions: The results show that collagen type IV alpha3 is an important factor in the development of corneal haze after PRK. Based on a quantitative PCR test, the individual collagen IV mRNA concentration in corneal epithelial cells could be measured. Further development could establish a screening test by which eyes with pronounced synthesis of collagen IV could be identified as being at high risk for haze after PRK. (C) 2002 ASCRS and ESCRS.