Corneal haze after photorefractive keratectomy. Role of individual collagen type IV synthesis on postoperative corneal opacity

PURPOSE: Histological studies on human corneas have shown that collagen type IV plays a major role in the development of haze after photoreactive keratectomy (PRK). Currently, there is no clinically available pharmaceutical agent which can inhibit the synthesis of collagen IV. The aim of this study was to determine if there are individual differences in the expression of collagen IV and if there is a correlation between the amount of collagen IV and haze. This would give new options to prevent haze after PRK. PATIENTS AND METHODS: PRK was carried out on 26 eyes (26 patients) with a myopia ranging between -1.50 to -6.00 D. Prior to the surgery a small sample of epithelium was taken from the cornea and the individual concentration of collagen IV alpha 3 mRNA was quantitatively determined by a newly developed PCR test. RESULTS: In all samples collagen IV alpha 3 mRNA was measured with levels between 0.11 and 6.42 (mean: 1.68; SD: 1.64). There was a correlation between haze and the amount of collagen IV alpha 3 mRNA. (r = 0.92). CONCLUSIONS: With this quantitative PCR-based test we were able to measure the individual collagen IV mRNA concentration in corneal epithelial cells. Further development of this test could establish a screening test which identifies patients with a pronounced synthesis of collagen IV as high risk individuals in terms of haze.