Interface quality of endothelial keratoplasty buttons obtained with optimised femtosecond laser settings

Aim: To optimise interfaces of endothelial buttons created with femtosecond (FS) lasers. Setting: Department of Ophthalmology, Hôtel-Dieu Hospital, Paris, France. Methods: Forty-two corneas were divided into five groups of various cutting patterns and a control group of 100 mm laser in situ keratomileusis flap creation. A single path full lamellar cut (500 mm) was applied to groups 1 and 2. The same full lamellar cut was applied twice to groups 3 and 4. Two successive lamellar cuts were performed in group 5 (350 and 150 mm). 60 kHz and 150 kHz were used respectively in groups 1, 3, 5, 6 and 2, 4. In each group, different laser settings were tested to obtain the best interface quality while delivering minimal energy to the stroma. The quality of stromal interfaces from created endothelial lenticules was observed using a scanning electron microscope. Results: Stromal adherences persisted after both the single- and double-path procedure, creating central irregularities on the endothelial lenticule. Among all groups and settings tested, the double-layer pattern (group 5) with FS full lamellar cut parameters set for diameter (mm), depth (mm), energy (mJ) and spot size/ step (mm) respectively on 9.0 mm, 350 mm, 2.1 mJ, 4:4 mm and 8.3 mm, 150 mm, 0.9 mJ, 4:4 mm created the smoothest interfaces with the best reproducibility. Conclusions: Buttons for endothelial keratoplasty can be created with FS laser with a stromal interface quality comparable with that of refractive surgery.