Background: The aim of this study is to present a new approach to visualize the aqueous outflow system during glaucoma surgery using a flexible microcatheter and fluorescein, called channelography.
Patients and methods: Schlemm's canal was unroofed in a standard non-penetrating dissection technique in patients undergoing canaloplasty. A flexible microcatheter (iTrack 250A) was introduced into the canal and advanced 360 degrees . Fluorescein sodium tracer was injected through the microcatheter during cannulation and the aqueous outflow pathway was video-recorded and evaluated.
Results: In the early phases, episcleral veins which were thinner, branched and fairly straight originating from the limbus could clearly be distinguished from ciliary veins which were thicker, tortuous vessels leaving posterior to the limbus. The filling quality of the episcleral veins varied among glaucoma patients. The permeability of the trabecular meshwork/inner wall of Schlemm's canal determined by fluorescein diffusion into the anterior chamber differed in this regard as well. In the late phases, the sclera stained with fluorescein, and no details were detectable.
Conclusions: This qualitative in-vivo method was simple, safe, and enabled us to visualize the details of the aqueous outflow system during canaloplasty. Filling characteristics of episcleral venous network as well as trans-trabecular diffusion may reflect the clinical status of the outflow pathway in glaucoma patients, and may be helpful in the prediction of the surgical outcome in canaloplasty.