The impact of vitreous humor: a new perspective on radiation-induced cataractogenesis

The precise mechanisms underlying radiation-induced cataractogenesis remain incompletely understood. Increased oxidative stress is known to play a central role in cataract pathogenesis. The vitreous humor contributes to maintaining the hypoxic environment of the lens by regulating oxygen pressure and containing antioxidants. This study aims to explore the effect of radiation-induced changes in the vitreous humor on lens health, with a particular focus on its cataractogenic potential.

In this experimental study, 12 New Zealand rabbits were utilized. A single 20-Gy dose of radiation was administered to the left eye's vitreous humor with a lens-sparing technique, while the right eye served as a control. Monthly ophthalmological evaluations were conducted over a 3-month period. At the end of the follow-up, orbital magnetic resonance imaging (MRI) was performed. Vitreous humor samples were analyzed using spectrophotometric methods to determine total oxidant and antioxidant levels.

Cataract formation was observed in two of the eight irradiated eyes (25%). The MRI analysis revealed a significant reduction in signal intensity within the left eye's aqueous humor in non-contrast sequences (p = 0.03), while an increase in signal intensity was observed in late post-contrast sequences (p = 0.04). Spectrophotometric analysis indicated that total oxidant levels (p = 0.04) and the oxidative stress index (p = 0.04) were significantly lower in the treatment group.

These findings suggest that radiation-induced changes in the vitreous humor and posterior ocular structures may influence the anterior chamber, contributing to the development of radiation-induced cataracts.