Abstract
Purpose :
Injection of an inert hydrogel into the suprachoroidal space (SCS) reduces intraocular pressure (IOP) as a potential treatment for glaucoma. Here, we examine the effect of SCS expansion on unconventional outflow and diurnal IOP patterns in rabbits.
Methods :
SCS injections of a hyaluronic acid-based hydrogel were performed by microneedles in normotensive New Zealand rabbits. IOP was monitored by tonometry, and SCS expansion was visualized by ultrasound biomicroscopy. Unconventional outflow was evaluated by the penetration depth into the SCS of a fluorescent dextran tracer (3kDa) after anterior chamber exchange, as analyzed from tissue sections in injected (n=4) and uninjected (control) eyes (n=2). Diurnal IOP patterns was examined by measuring IOP every 3 h over 24 h in rabbits (n=3) treated sequentially as follows: control, timolol eye drops, and recent (10 days prior) hydrogel injection. Diurnal IOP was also measured in rabbits (n=2) with long-term hydrogel injections (>6 months prior). Statistical analysis used one-way ANOVA.
Results :
Tracer was observed in the SCS, sclera, and hydrogel. SCS penetration depth was 4.6±1.5mm posterior to the iridocorneal angle in a quadrant with hydrogel (mean±SD) vs 1.2±0.4mm in a quadrant without hydrogel (p=0.0052) and 1.1±0.6mm in control eyes (p=0.0128; Fig 1). Hydrogel injection reduced IOP for >6 months (Fig 2A). Overall in 24hrs, recent hydrogel injections resulted in reduced IOP compared to control and timolol treatment (p≤0.0001; p≤0.0001) (Fig 2B); long-term hydrogel injection reduced IOP vs. control (p=0.0016; Fig. 2B). While hydrogel-injected eyes experienced diurnal IOP variations, both recent and long-term injected eyes had greater % IOP reduction (from control) compared to timolol (p≤0.0001; p= 0.0017) (Fig 2C).
Conclusions :
Hydrogel expansion of the SCS increased unconventional outflow as assayed by tracer penetration, had a greater percentage decrease in IOP than timolol in a 24-hr period, and can maintain IOP reduction for >6 months in rabbits.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.