How does viscocanalostomy work? A new concept to the mode of action using scanning electron microscopy

Abstract

Abstract: : Purpose: Several studies have proven the efficacy of viscocanalostomy as a non–penetrating approach in glaucoma surgery. The mechanism responsible for the decrease in intraocular pressure has not been clarified in detail.Methods: From a pool of over 200 patients having undergone standardized viscocanalostomy performed by one surgeon 45 eyes were selected for this study. 20 eyes were defined as a long–term success, whereas in 25 eyes, a repeat operation was necessary. The resected deep scleral flap was investigated using scanning electron microscopy. Morphological findings were correlated with the clinical outcome. Results: In 40 scleral flaps (89%), tissue of Schlemm’s canal was found. Absence of Schlemm’s canal correlated with early postoperative failure (p<0.05). The amount of anterior trabecular meshwork correlated well with the long–term success (p<0.01). The number of septae in Schlemm’s canal showed a significant coherence to the incidence of postoperative hypotony (p<0.001), whereas there was no significant correlation to the success rate.Conclusions: Schlemm’s canal was precisely deroofed in most of the cases. A deep sclerectomy without resection of anterior meshwork seems to have a lower effect on reduction of IOP. A microperforation of the inner wall of Schlemm’s canal due to resection of septae leads to a higher risk of early postoperative hypotony, but has no influence on long–term results.

Keywords: microscopy: electron microscopy • outflow: trabecular meshwork • sclera