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Correlations between risk factors and haze after PRK identified
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A large cohort study investigating factors associated with the development of haze after PRK found significant correlations with hyperopia, high myopia and high astigmatism. Longer mitomycin C application and laser removal of the epithelium rather than alcohol debridement, however, may have a beneficial effect on haze prevention.
A total of 7,535 eyes of 3,854 patients who underwent PRK over 2 years were retrospectively reviewed. The epithelium was removed with the application of alcohol or by laser ablation. All PRK procedures were performed with the WaveLight EX200 Allegretto Wave laser (Alcon). MMC was applied for between 20 and 60 seconds.
The highest incidence of haze was found in hyperopic eyes (10.8%). Eyes with myopia of 6 D or higher had double the incidence of haze (2.1%) compared with eyes with low and moderate myopia (1.1%), as well as a higher incidence of severe haze. Patients with preoperative astigmatism higher than 3 D had more haze than patients with low astigmatism (2.9% vs. 1%).
An MMC application time of 40 seconds or longer was protective against haze in all groups, leading to 0% haze in moderately myopic and hyperopic eyes.
The method of epithelium removal also played a role: The incidence of haze was 2.6 times higher with the use of alcohol as compared with laser. According to the authors, “this might be attributable to a toxic effect of alcohol on the epithelial cells and the anterior stroma, and also to the uneven margins of the wound,” or more likely to the fact that “trans-PRK induces far less keratocyte death than blade scrape epithelial removal PRK.”– by Michela Cimberle
Disclosures: The authors report no relevant financial disclosures.
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