Femtosecond laser top hat penetrating keratoplasty: Wound burst pressures of incomplete cuts

Objective: To investigate the pressure required to rupture femtosecond laser top hat configuration corneal dissections with incomplete dissections. Methods: Twenty corneoscleral buttons underwent femtosecond laser top hat configuration dissections. Group A had complete dissections; group B, 100-μm gaps in the anterior side cut; group C, 50-μm gaps in the anterior side cut; group D, 100-μm gaps in the lamellar cut; and group E, 50-μm gaps in the lamellar cut. The pressure required to rupture each cornea was measured. Results: The mean (SD) pressure required to rupture the corneas was 111 (74) mm Hg for group A, 1565 (509) mm Hg for group B, 747 (209) mm Hg for group C, 550 (303) mm Hg for group D, and 392 (166) mm Hg for group E (P = .03 for all compared with group A). Conclusions: Incomplete femtosecond laser top hat dissections are highly resistant to rupture by direct pressurization. Gaps in the anterior side cuts are stronger than comparably sized gaps in the lamellar cuts. Clinical Relevance: Undertaking femtosecond laser keratoplasty in a 2-site setting should, theoretically, have a high level of safety. Burst pressures are high enough to resist an inadvertent sudden increase in intraocular pressure providing that incomplete recipient laser dissections are undertaken.