Increased episcleral venous pressure in a mouse model of circumlimbal suture induced ocular hypertension.

Abstract Purpose To investigate changes in aqueous humor dynamics during intraocular pressure (IOP) elevation induced by circumlimbal suture in mice. Methods Ocular hypertension (OHT) was induced by applying a circumlimbal suture behind the limbus in male adult C57BL6/J mice. In the OHT group, the suture was left in place for an average of 8 weeks (n = 10, OHT group). In the sham control group the suture was cut at 2 days (n = 9, sham group) and in the naive control group (n = 5) no suture was implanted. IOP was measured at baseline across 3 days, 1 h post-suture implantation, and at the chronic endpoint. Anterior segments were assessed using optical coherence tomography (OCT). Episcleral venous pressure (EVP), total outflow facility (C), uveoscleral outflow (Fu) and aqueous humor flow rate (Fin) were determined using a constant-flow infusion model. Results All aqueous dynamic and chronic IOP outcome measures showed no difference between sham and naive controls (p > 0.05) and thus these groups were combined into a single control group. IOP was elevated in OHT group compared with controls (p   0.05). EVP was significantly higher in OHT eyes compared to control eyes (p   0.05). A significant linear correlation was found between IOP and EVP (R2 = 0.35, p = 0.001). Conclusions Circumlimbal suture implantation in mouse eyes results in chronic IOP elevation without angle closure. Chronic IOP elevation is likely to reflect higher EVP.