Abstract
Abstract: :
Purpose: Treatment of human patients with hyperbaric oxygen (HBO) is known to induce reversible myopia. The aim of this study was to 1) determine if HBO treatment could induce myopia in guinea pigs, and 2) determine whether a correlation existed between the in vivo refractive status of the eye and the in vitro focal length status of the lenses, post-HBO treatment. Methods: Animals were exposed to 100% O2 @ 2.5 atm for 2.5 hr periods, 3x a week with the total number of treatments at 35 or 70. Retinoscopy was performed on both eyes of treated animals and untreated controls before euthanasia. Nuclear light scatter was evaluated using slit-lamp biomicroscopy. Lenses were dissected and placed in a two-compartment 25 ml chamber containing culture medium supplemented with 1% penicillin/streptomycin and 3% fetal bovine serum. The optical quality of the lenses was measured using a real-time scanning laser system. Results: The lenses of the treated animals showed an increase in nuclear light scattering as shown by slit-lamp. The 35-HBO-treated animals showed significant myopia (treated, -6.00 diopters vs control, -0.50 diopters; P = 0.001) and the lenses showed shorter focal lengths (treated, 8.26 mm vs control, 8.86 mm; P = 0.034). While the 70-HBO-treated animals were not significantly different from the control for in vivo assessment, lens optical quality showed a significant decrease in the treated group (focal length variability: treated, 0.31 mm vs control, 0.15 mm; P = 0.02). Conclusions: These findings show that the 35-HBO-treatment caused myopia in guinea pigs, while at 70-HBO-treatment the response rate of the refractive system appeared to display some saturation with no significant myopia. However, the lenses from the 70-HBO-treated animals exhibited higher focal variability. A correlation between the in vivo and in vitro results is demonstrated. The shorter focal lengths in the 35-HBO-treated group suggest a lenticular role in the reversible HBO-induced myopia as reported elsewhere for humans.
Keywords: 316 animal model • 481 myopia • 592 stress response