Ascorbic acid levels in human tears after photorefractive keratectomy, transepithelial photorefractive keratectomy, and laser in situ keratomileusis

Purpose: To investigate the level of ascorbic acid in human tear fluid afte r photorefractive keratectomy (PRK), transepithelial PRK, and laser in situ keratomileusis (LASIK). Setting: Departments of Ophthalmology and Biochemistry, School of Medicine, Gazi University, Ankara, Turkey. Methods: Twenty patients (7 women and 13 men) were included in this study. Traditional PRK with epithelial scraping by a blunt spatula followed by sur face ablation (7 eyes), transepithelial PRK (7 eyes), or LASIK (6 eyes) was performed. Tears were collected preoperatively and 1 and 5 days postoperat ively, Ascorbic acid levels were measured using 2-4 dinitrophenylhydrazine. Results: Ascorbic acid levels in the tear fluid were decreased significantl y 1 day after PRK, 'transepithelial PRK, and LASIK (P <.05). On the fifth d ay, the ascorbic acid levels were significantly lower than preoperatively i n all groups. Conclusion: After PRK, transepithelial PRK, and LASIK, the ascorbic acid le vels of the tear fluid decreased significantly. Because ascorbic acid is th e major scavenger of superoxide radicals in tears, topical ascorbic acid th erapy may help eliminate the harmful effect of free radicals from excimer l aser surgery.