Real-Time Monitoring of Suprachoroidal Space (SCS) Following SCS Injection Using Ultra-High Resolution Optical Coherence Tomography in Guinea Pig Eyes.

Abstract

To monitor the change of suprachoroidal space (SCS) using ultra high resolution-optical coherence tomography (UHR-OCT) following SCS injection with different drug formulations. An amount of 10 or 20 μL of saline or indocyanine green (ICG) or triamcinolone acetonide (TA) suspension (40 or 80 mg/mL) was injected suprachoroidally into the guinea pig eye with a 30-gauge needle. Immediately after injection, the eyes were imaged by UHR-OCT from 60 minutes up to 24 hours. At each time point, the SCS area on each OCT cross-section was measured in pixels with Image J and the area change from the baselines was analyzed over time. A 20-μL injection produced 130% to 200% SCS expansion compared to a 10-μL injection for saline and TA suspension (P < 0.01). After SCS injection, the time that expansion persisted was formulation dependent. Thus, expansion in response to injection of TA suspension, ICG, and saline persisted for 24 hours, 180 minutes, and 60 minutes, respectively. Moreover, ICG injection produced a significantly larger area of distribution in the SCS than the TA suspension (0.626 vs. 0.275 cm(2), P < 0.0001). The SCS is expandable and can recover to preinjection status after injected fluid is cleared by physiological processes. The injection-induced SCS expansion is volume-dependent, and the drug/dye retained in the SCS is formulation-dependent. The current injection technique with a volume of 20 μL or less is well tolerated in guinea pig eyes.