Corneal cisterns as drainage aqueducts

Importance Anterior chamber paracentesis (ACP) is a known method of rapid reduction of IOP. The mechanism of how corneal fluid clears after ACP is not well described. Objective To determine the mechanism of instantaneous corneal clearing of edema after ACP. Design, setting, and participants This case series includes consecutive patients with high IOP and associated corneal edema, who presented to the Glaucoma Services of our tertiary care center. Pre- and post-intervention (ACP) ASOCTs were analyzed. Main outcome measures Resolution of corneal edema (clinical picture) and imaging of peripheral cornea and iridocorneal angle area. Results Ten consecutive patients who underwent an ACP were included in this study. The mean IOP pre-intervention was 48.4 ± 8.2 mmHg. ASOCT showed ill-defined conventional pathways of aqueous outflow, which were blocked by peripheral anterior synechiae in 4 eyes. Immediately post ACP, the IOP was 16.3 ± 5.6 mmHg (p < 0.001) and corneal edema resolved immediately. We found on ASOCT, that the intrastromal hypolucency of the peripheral cornea, (corneal cistern) which was limited in extent and U shaped, showed a posterior extension into the corneo-limbal junction to form well-defined anastomoses with the conventional aqueous drainage channels demonstrating a direct conduit for intracorneal fluid to egress. In 2/10 eyes, Schlemm’s canal opened intracamerally as well, suggesting direct reflux of intra-corneal fluid into the anterior chamber. Conclusion and Relevance After an ACP, in eyes with corneal edema to relieve IOP, we observed that the intracorneal cisterns undergo peripheral extension to drain corneal fluid through the conventional distal outflow channels.