Chronic ocular hypertension induced by circumlimbal suture in rats

PURPOSE: To induce chronic intraocular pressure (IOP) elevation in rat eyes by circumlimbal suture. METHODS: Anesthetized (isoflurane) Long-Evans rats underwent unilateral circumlimbal suture implantation while the fellow eyes served as untreated controls (n=15). A sham group (n=8) received the same procedure except the suture was loosely tied. IOP, electroretinography (ERG) and optical coherence tomography (OCT) were monitored for 15 weeks, after which retinal histology and immunofluorescence staining for glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule-1 (Iba-1) were undertaken. RESULTS: Both IOP and ERG remained unaltered in the sham and all control eyes over 15 weeks. In the ocular hypertensive eye, IOP spiked from 17+/-1 to 58+/-3 mmHg immediately after suture application, recovering to 32+/-2 mmHg by 24 hours, and remained elevated by 7-10 mmHg above baseline for 15 weeks. At week 2, there was a small reduction of ERG components involving the photoreceptor a-wave, bipolar cell b-wave, and ganglion cell mediated Scotopic Threshold Response (pSTR). The reduction in a- and b-wave remained stable, while the pSTR became more affected from week 8 onwards (p