"Coming up short" with an illuminated microcatheter for circumferential trabeculotomy externo in the buphthalmic infant eye: frequency and options.

An illuminated microcatheter is frequently used to perform trabeculotomy ab externo in infants with primary congenital glaucoma (PCG). Enlarged corneas in these children can make it challenging to traverse 360o of Schlemm's canal (SC) before reaching the passable limit of the microcatheter. Using basic geometry, we predicted that the iTrack microcatheter would fail to cannulate SC completely in eyes with a horizontal corneal diameter (HCD) >14.8 mm. A retrospective chart review of patients with PCG undergoing angle surgery identified the frequency of corneas with HCD >14.8 mm and confirmed that this calculated cut-off predicts which eyes can-or cannot-be cannulated successfully (ie, 360o) by the iTrack microcatheter.