Does the dissection depth and thickness of the deep scleral flap influence the intraocular pressure after viscocanalostomy?: A clinico-pathologic correlation

Background: Non-perforating glaucoma surgery preserves the integrity of the trabecular meshwork in order to avoid postoperative hypotony. The purpose of our study was to investigate whether the morphologic variability of the excised deep scleral flap influences the postoperative intraocular pressure (IOP) after viscocanalostomy. Methods: Light-microscopy of the deep scleral flap was performed in 17 patients who had undergone viscocanalstomy. Morphologic parameters (thickness and dissection level of the deep scleral flap) were correlated with the postoperative IOP. Results: The mean thickness of the deep scleral flap was 309 +/- 95 mum; the dissection level was too deep in 5 cases (trabecular tissue excised) and too high in 6 cases (no signs of Schlemm's canal). The max. preop. IOP was 36.2+/-8.5 mmHg and came down to 10.6+/-5.7 mmHg at day 1 postop. and 12.4 +/- 4.9 mm Hg at day 3/4 postop. At a median follow-up of 6 months IOP was 21.7 +/- 5.5 mm Hg. A significant correlation between postop. IOP and the morphology of the deep scleral flap could not be demonstrated. Conclusions: Variations of the thickness and depth of the deep scleral flap showed little influence on the initial IOP level following viscocanalostomy. Other factors, f.e. the suturing of the external flap or invisible microruptures of the trabecular meshwork, could be of importance for the early postoperative IOP.