RELATIVE STABILITY OF CLEAR CORNEAL INCISIONS IN A CADAVER EYE MODEL

Three different clear corneal square incisions-beveled (or paracentesi s), stepped, and hinged-were studied in a cadaver eye model to determi ne whether a critical width existed for each incision type at which re sistance to external pressure changed substantially, given identical t unnel length (1.75 mm to 2.00 mm) for each incision. As a comparison, the beveled (paracentesis) incision was also performed as a clear corn eal incision at the anterior limbus, making it a limbal beveled incisi on. 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 provid ed additional support in resisting externally applied pressure. When t he clear corneal beveled technique is used, incision width should be 3 .0 mm or less. When clear corneal stepped or hinged techniques are use d, incision width should be 3.5 mm or less. Finally, it appears that a ll clear corneal incisions should be made as close to the anterior lim bus as possible to achieve the greatest structural support.