Abstract
Purpose:
To develop a reliable and cost-effective model of chronic ocular hypertension which mimics glaucomatous optic neuropathy in rat.
Methods:
Long-Evans rats were given unilateral ligation around the limbus via conjunctival suture under anaesthesia (ketamine/xylazine). The fellow eye served as an untreated control (n=8). A sham group (n=8) received the same unilateral treatment except the suture was loosely placed. IOP was monitored pre- and post-ligation for 15 weeks. Electroretinography (ERG) was recorded at baseline (pre-suture), then regularly to 15 weeks. The photoreceptor, bipolar cell and ganglion cell function were extracted and expressed relative to the contralateral untreated control eye (%±SEM).
Results:
During the first day after ligation, IOP spiked from 16.9±0.8 to 58.2±4.3 mm Hg recovering to 29.9±1.9 mm Hg in treated eyes (p<0.05) and remained elevated for 15 weeks. The sham group gave a small temporary spike (22.8±2.8 mm Hg at 1-hour) before returning to normal. Control eyes remained at normal IOP (baseline 16.4±0.9 mm Hg, week 15 11.7±0.2 mm Hg, p > 0.05). In ligated eyes, an early non-selective loss of all ERG components was manifest. From week 8, a selectively larger loss of ganglion cell function compared with bipolar cell and photoreceptor function was found (-36±7% vs -21±7% vs -16±7% respectively; p<0.05). ERG components remained unaltered in the sham group for 15 weeks (4±5%, -3±5%, -2±4% respectively; p > 0.05).
Conclusions:
Circumlimbal ligation provides a simple and cost-effective way to induce mild chronic ocular hypertension that produces preferential ganglion cell dysfunction. This model may be useful in glaucoma research.
Keywords: 568 intraocular pressure •
510 electroretinography: non-clinical •
531 ganglion cells