Optimizing interface of Endothelial Keratoplasty buttons with femtosecond-assisted procedure

Abstract

Purpose: : With femtosecond lasers (FS), the cutting step to create Endothelial Keratoplasty (EK) lenticules is highly reproducible. However, the FS procedure generates irregularities of interface (Rousseau, ARVO 2011), which participate in disappointing visual results. Aiming to improve the FS-assisted EK procedure, we have evaluated a double layer approach to create EK lenticules with FS and even button’s interface, while lowering the amount of energy delivered.

Methods: : Sixteen human organ-cultured corneas were obtained and deswelled for experimental use. To create EK lenticules, a double layer precut procedure was performed with the 60 kHz FS (Intralase AMO) with two successive steps of aplanation. For full lamellar cuts, energy was set respectively to 2.3, 2.2, 2.1, 1.2 µJ for step 1 and to 1.2, 1.1, 1.0, 0.9, 0.8 µJ for step 2. A 120 µm thick LASIK flap served as control. The resistance to dissect interfaces was evaluated on a 0 to 5 grades semi-quantitative scale. Stromal interfaces were analyzed with a scanning electron microscope (SEM).

Results: : Two incomplete dissections (grade 4) occurred with 1.2 µJ step1 and 0.8 µJ step2. Small residual collagen bridges (grade 1 and 2) were observed at the interface of the central area, when energies were set below 2.1 µJ (step1) and 0.9 µJ (step2). SEM revealed button’s interfaces with similar smoothness compared to the LASIK control, at the energy of 2.1 µJ (step1) and 1.0 µJ (step2).

Conclusions: : With appropriate energy levels and cutting profile to create EK lenticules, FS-assisted procedure reliably generates smooth interfaces, similar to LASIK flap interfaces.

Keywords: cornea: endothelium • transplantation • laser