Long-term safety evaluation of suprachoroidal space following multiple suprachoroidal injection of triamcinolone acetonide (TA)

Abstract

Purpose : Suprachoroidal space (SCS) injection is an emerging technique to deliver drugs to the posterior segment. SCS drug administration is less invasive than intravitreal injection and more efficient than subtenon injection, bypassing clearance of the blood and lymphatic circulation a conjunctiva and episclera. However, long-term SCS changes following multiple injections are not well understood yet.

Methods : Six rabbit eyes were subjected to one to three consecutive bimonthly SCS injections of 50µL TA suspension. Prior to each injection, intraocular pressure (IOP), indirect ophthalmoscopy, and Ultrahigh Resolution Optical Coherence Tomography (UHR-OCT) were performed. Electroretinography (ERG) readings were collected prior to sacrifice. The area that encloses the space between the inner scleral wall and the RPE was measured in pixels on the cross sections of UHR-OCT at the injection site. Additional six rabbits had both eyes injected with 10% Acrylonitrile Butadiene Styrene (ABS in acetone and butanone 1:1) 20 minutes before sacrifice. The eye globe was corroded in 10% natrium hydroxide until the cast of the SCS was freestanding. The casting was imaged along with a ruler on the scleral side and holes smaller than 500µm were counted with a custom-written program. We hypothesize that the small holes on the cast may represent fluid channels between the choroid and the sclera.

Results : No clinical abnormalities were noted through the course of the study. The average IOP of the injected eyes versus their fellow eyes was 13.8±1.66 vs. 13.1±1.82 (p=0.002 paired t-test). The areas measured by imageJ on UHR-OCT cross sections showed no significant difference between the injected eyes and their contralateral eyes (at 8 weeks injected 1.01±0.09 vs. contralateral 0.94±0.18, p=0.24; at 16 weeks 0.74±0.2 vs. 0.87±0.17, p=0.02; at 24 weeks 1.08±0.14 vs. 1.18±0.19, p=0.35). There was also no difference in ERG b-wave amplitudes between the injected and the control eyes (flicker ERG, 59.7±20.1µV vs. 61.2±27µV, p=0.8). The small holes on the casting for the injected eye was 364.2±189.6 vs. 476.7±116.5 for the control eyes (p=0.035, paired t-test).

Conclusions : It seems suprachoroidal injections of TA at a volume of 50 µL were well tolerated in the rabbit eye, even with multiple injections. The suprachoroidal may experience subtle changes following the injections.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.