Post-Operative Hypotony After 25-Gauge Sutureless Vitrectomy Using Oblique versus Direct Cannula Insertions

Abstract

Purpose:: To compare intraocular pressure and rates of post-operative hypotony in patients undergoing 25-gauge transconjunctival sutureless vitrectomy (TSV) using an oblique cannula insertion technique versus the conventional direct cannula insertion technique.

Design:: Retrospective, observational case series.

Methods:: Eighty-four consecutive patients underwent 25-gauge TSV, forty-four using an oblique insertion technique for the three-port 25-gauge cannulas and forty using the conventional direct insertion technique. Intraocular pressures (IOP) were recorded at each patient’s visit before surgery, post-operative day 1, and post-opererative week 1.

Results:: Using the oblique insertion technique, mean post-operative day 1 IOP of 16.5 ± 7.5 mm Hg did not differ significantly from the mean pre-operative IOP of 16.0 ± 4.1 mm Hg (p = 0.71). Mean post-operative week 1 IOP was 16.6 ± 5.0 mm Hg which was not significantly different from the pre-operative IOP (p = 0.45)) or post-operative day 1 IOP (p = 0.89). Only one of the 44 patients (2.3%) had hypotony (IOP ≤ 6 mm Hg) post-operative day 1. Using the conventional direct insertion technique, mean post-operative day 1 IOP of 13.6 ± 5.3 mm Hg was statistically significantly lower than the mean pre-operative IOP of 15.8 ± 3.9 mm Hg (p = 0.009). Mean post-operative week 1 IOP of 15.2 ± 5.2 mm Hg did not differ significantly from the mean pre-operative IOP (p = 0.48). Four of the 40 patients (10%) had hypotony post-operative day 1.

Conclusions:: The oblique cannula insertion technique is superior to the conventional direct cannula insertion for lowering rates of absolute and relative post-operative day 1 hypotony in patients undergoing 25-gauge TSV. By creating a shelved incision with the oblique technique, better wound closure may be achieved which could also theoretically decrease the rate of endophthalmitis.

Keywords: vitreoretinal surgery • retina