[The study of photorefractive keratectomy induced defocus on emmetropization in infant monkeys].

OBJECTIVE: To investigate the effect of photorefractive keratectomy (PRK) induced defocus on emmetropization in infant rhesus monkeys and to determine the role of visual feedback on emmetropization. METHODS: PRK was performed in 8 healthy rhesus monkeys age ranging from 2 to 3 months. Either 3.00 D of relative hyperopic or myopic defocus was produced in one eye and the fellow eye as controls. The eyes were examined periodically with corneal topography, cycloplegic retinoscopy, A-scan ultrasonography, and slit-lamp biomicroscopy. RESULTS: All operated eyes demonstrated re-epithelialization within 3 days post-surgically and maintained transparent. Compensating axial length growth occurred throughout the observation period. The rate of vitreous chamber elongation varied with the post-PRK refractive status of the eye. The hyperopia-induced eyes exhibited a vitreous chamber elongation faster than the fellow eyes (t = 3.656, P = 0.0354), whereas myopia-induced eyes demonstrated a vitreous chamber elongation slower than the fellow eyes (t = 3.576, P = 0.0374). CONCLUSIONS: PRK-induced-defocus altered axial growth rates and emmetropization in infant monkeys predictably. These results indicate that primate emmetropization is regulated by visual feedback and correction of refractive error on children should be careful. PRK-induced-defocus is a promising method for myopic animal model and for the investigation of vision science.