Femtosecond Laser Cutting of Endothelial Grafts: Comparison of Endothelial and Epithelial Applanation

Laser-assisted corneal transplantation surgery

Corneal transplant surgeries have a broad range of indications with outcomes largely dependent on surgeon experience. Traditional manual techniques have certain limitations pertaining to the preparation of donor tissue and the recipient bed that might affect the predictability of visual outcomes. Use of lasers for keratoplasty procedures not only improves the repeatability and consistency of the technique, but also enables the surgeon to control the thickness and shape of the transplant tissue tailored to the specific condition. Despite the advantages, cost-effectiveness and technical know-how remain the major challenges. We discuss the various techniques of laser-assisted keratoplasties with respect to their methods, precision, and efficacy in various corneal indications.

Surface quality and endothelial cell viability after femtosecond laser-assisted donor lenticule preparation for endothelial keratoplasty - An in-vitro study

Purpose

To compare surface quality and endothelial cell viability of descemet stripping automated endothelial keratoplasty (DSAEK) donor lenticules prepared with femtosecond laser (FSL) or microkeratome (MK).

Methods

Experimental ex-vivo evaluation of 15 DSAEK donor lenticules prepared from optical quality donor corneas using 200 KHz FSL (9 eyes) or MK (6 eyes). Surface quality and smoothness of the cut were assessed using atomic force microscopy and endothelial cell viability was assessed using transmission electron microscopy.

Results

Mean lenticule thickness was 121.89 ± 17.13 μm in FSL group and 112.67 ± 5.89 μm in MK group (P = 0.33). Average roughness of stromal surface (RMSavg) [FSL- 30.51 ± 4.55 nm, MK-22.37 ± 1.83 nm; P = 0.02] and root mean square roughness (RMSrough) [FSL-31.39 ± 5.75 nm, MK-23.08 ± 0.40 nm; P = 0.012] was significantly more in FSL group. Increased granular and linear irregularities were observed in the FSL group. Endothelial cell disruption was more in FSL group (FSL- 29.49 ± 6.91% MK-13.28 ± 3.62%; P < 0.001) with decreased mean nucleus length (FSL-5.56 ± 0.17 μm, MK-7.52 ± 0.65 μm; P < 0.001).

Conclusion

Automated MKs are still the standard of care for donor lenticule preparation and MK-assisted donor lenticules have smoother surface with less endothelial cell disruption than FSL. Further research is mandatory before FSL platforms can be considered a viable alternative to the MK.

Technical Feasibility of Isolated Bowman Layer Graft Preparation by Femtosecond Laser: A Pilot Study

Purpose

To evaluate the technical feasibility of isolated Bowman layer (BL) graft preparation by femtosecond laser (FSL) and to compare the ultrastructural morphology to manually dissected grafts.

Methods

Five whole globes were placed in custom-made eye holders and debrided of epithelium. After programming a dissection depth of 20 μm, the FSL was docked into position and 5 isolated BL grafts were created. From 5 additional globes, corneoscleral buttons were procured, mounted in artificial anterior chambers, and stripped of BL via the previously described manual technique. Three specimens from both series were randomly selected and assigned to transmission electron microscopy for ultrastructural evaluation and thickness measurements.

Results

All dissections were uneventful and 10 total grafts were produced: 5 by FSL and 5 by manual dissection. Mean graft thickness was 37 (±8.6) μm (n = 3) for the FSL group and 11.7 (±1.6) μm (n = 3) for the manually dissected group. Transmission electron microscopy revealed a thick but relatively smooth posterior cut edge in the FSL group, versus a virtually isolated BL with irregular rests of dispersed stroma in the manually dissected group.

Conclusions

Femtosecond laser may have potential for harvesting intact BL and with a smooth posterior surface, but accompanied by variable amounts of anterior stroma owing to technical limitations.