Abstract and Introduction
Abstract
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 μm laser in situ keratomileusis flap creation. A single path full lamellar cut (500 μm) 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 μm). 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 (μm), energy (μJ) and spot size/step (μm) respectively on 9.0 mm, 350 μm, 2.1 μJ, 4:4 μm and 8.3 mm, 150 μm, 0.9 μJ, 4:4 μm 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.
Introduction
Endothelial lamellar keratoplasty (ELK) involves the selective replacement of damaged endothelium. The endothelial button (or lenticule) can be prepared with either a microkeratome or a femtosecond laser (FS). Microkeratome lamellar dissection is cheap and well standardised, and provides buttons with smoother interfaces compared with FS precutting. Smoother stromal interfaces can be used for long-term visual outcomes. On the other hand, lamellar cuts are restricted to depth adjustments by microkeratome headsizes, and the button thickness is poorly reproducible. Microkeratomes are subject to possible blockade during the cutting phase, which impairs the regularity of the button's interface.
The FS has many advantages over microkeratome in precutting endothelial keratoplasty lenticules. It cuts corneal tissue at every chosen profile. It can be standardised and reproducible, thus reducing any problems related to dissection. Both the safety and reliability of corneal lamellar FS cuts have been demonstrated extensively for laser in situ keratomileusis (LASIK) and recently for ELK. Buttons created with FS are more planar-shaped and thinner when obtained with FS, which could be beneficial for visual outcomes. However, the smoothness and regularity of the stromal interface still need to be improved, and the laser settings optimised for femtosecond laser endothelial keratoplasty. To address this, we tested various FS precutting profiles with customised settings to generate a smoother and regular interface on lenticules.