A rabbit model of age-dependant ocular hypertensive response to topical corticosteroids.

. Objective:  To investigate the ocular hypertensive response to topical dexamethasone (DEX), rimexolone (RIM), loteprednol etabonate (LOT) and fluorometholone (FML) in rabbits of different ages. Methods:  Seventy-five rabbits of three age groups (7 weeks, 6 months and 1-year old) received topical administration of 0.1% DEX, 1% RIM, 0.5% LOT, 0.1% FML or balanced salt solution four times daily for 1 month. Intraocular pressure (IOP) was monitored at regular time intervals. After a month, eyes were harvested for histological study with haematoxylin and eosin (H&E), periodic acid Schiff and Masson trichrome staining. Trabecular meshwork changes were graded by masked ocular pathologists. Results:  Topical DEX caused the greatest increase in IOP, followed by RIM and FML. LOT caused the least IOP increase. Similar pattern of IOP response to the four corticosteroids was observed in the three studied age groups. Young rabbits (7 week) were the most responsive to corticosteroids among the age groups. Extracellular matrix thickening in the trabecular meshwork region and loss of trabecular meshwork cells were observed after DEX, FML or RIM treatments. Conclusion:  Young rabbits are more susceptible to steroid induced increase in IOP, even for milder steroids such as fluorometholone and rimexolone.