Relative stability of clear corneal incisions in a cadaver eye model

Abstract

Three different clear corneal square incisions—beveled (or paracentesis), stepped, and hinged—were studied in a cadaver eye model to determine whether a critical width existed for each incision type at which resistance to external pressure changed substantially, given identical tunnel length (1.75 mm to 2.00 mm) for each incision. As a comparison, the beveled (paracentesis) incision was also performed as a clear corneal incision at the anterior limbus, making it a limbal beveled incision. One surgeon performed all procedures. Incision width ranged from 2.5 mm to 5.0 mm in 0.5 mm increments. External pressure as high as 525 psi was applied to all eyes at two ranges of intraocular pressure (10 mm Hg to 15 mm Hg and 20 mm Hg to 25 mm Hg) to determine the relative ability of each incision type to resist leakage. The hinged incision performed better than the stepped and corneal beveled incisions. When the beveled (paracentesis) incision was made as a clear corneal limbal beveled incision at the anterior limbus, the limbal structures provided additional support in resisting externally applied pressure. When the clear corneal beveled technique is used, incision width should be 3.0 mm or less. When clear corneal stepped or hinged techniques are used, incision width should be 3.5 mm or less. Finally, it appears that all clear corneal incisions should be made as close to the anterior limbus as possible to achieve the greatest structural support.