Abstract
Purpose :
Suprachoroidal space (SCS) expansion via microneedle (MN) using a single injection of an inert hydrogel reduces intraocular pressure (IOP) in ocular normotensive (NT) rabbits. This is a novel, potential treatment for glaucoma (Chae at al., Adv Sci, 2021). Here we examined the effect of repeat injections on IOP in rabbits and single injections on IOP in NT and ocular hypertensive (HT) cynomolgus monkeys.
Methods :
NT New Zealand White rabbits received two SCS injections in the same eye at least 6 months apart (n=2). Cynomolgus monkeys received single MN hydrogel injections in NT (n=7) and HT eyes (n=6); controls received sham saline MN injections (n=2 NT, n=3 HT). Hydrogels were based on hyaluronic acid or other materials, with injection volumes of 50 µl (rabbits, HT monkeys) or 100 µl (NT monkeys). IOP and eye wall thickness (EWT), a measure of SCS expansion, were monitored by tonometry and ultrasonography.
Results :
After single and repeat injections in rabbits, IOP initially dropped by ~4 mmHg, while EWT correspondingly increased by ~2-3 mm, both returning to baseline over 2-3 months (Fig. 1). The second injection had a similar effect on IOP as the first since regression fits to single and repeat injections were not statistically different (p=0.41). Similar effects on IOP were seen in monkeys, but with faster kinetics (Fig. 2). In NT and HT eyes, IOP initially dropped by ~8 and 15 mmHg and was reduced for 38.8 [33.2, 44.4] and 42.7 [29.6, 55.9] days, respectively, and hydrogel injections had a different effect on IOP compared to sham (saline) injections since individual regression fits differed (p<0.0001). In HT and NT eyes, EWT increased by ~2-3 mm and then gradually decreased for 1-2 months.
Conclusions :
A second SCS hydrogel injection was as effective at IOP lowering as the first. IOP reduction via SCS hydrogel injection occurred in both monkeys and rabbits; however, the duration of IOP lowering was shorter in monkeys. Further formulation optimization is ongoing to extend the IOP lowering effect.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.