Nonmechanical Q-Switched Erbium:YAG Laser Trephination for Penetrating Keratoplasty

Abstract

To assess the alterations in human donor corneal tissue induced by Q-switched erbium (Er):YAG laser corneal trephination. Methods: Thirty human corneoscleral donor buttons unsuitable for transplantation were placed in an artificial chamber on an automated rotation device. Corneas were trephined with a Q-switched Er:YAG laser (wavelength, 2.94 µm; pulse duration, 400 nanoseconds) along (donor and recipient) aluminum silicate (ceramic) open masks. A spot diameter of 0.65 mm, energy setting of 50 mJ/pulse, and repetition rate of 5 Hz were used. Corneal thermal damage and cut regularity were quantitatively assessed in 24 corneas processed for light microscopy and by transmission and scanning electron microscopy. Results: The stromal thermal damage was the highest (mean [SD], 8.0 [2.7] µm) at a 150-µm cut depth and decreased downward. Cut regularity was very good and did not significantly differ between donors and recipients. Scanning electron microscopy confirmed that the cuts were highly regular; transmission electron microscopy revealed 2 distinctive subzones within the stromal thermal damage zone. Conclusions: Thermal damage induced by Q-switched Er:YAG nonmechanical corneal trephination was low, and the regularity of the cuts was very good. Clinical Relevance: The Q-switched Er:YAG laser may have the potential to become an alternative to the excimer laser for nonmechanical penetrating keratoplasty.

Electron microscopic comparison of the donor cut edges using femtosecond laser-assisted keratoplasty versus conventional keratoplasty

“…They reported the thermal effect in the form of band of carbonization and a coagulation zone associated with collagen and cellular damage. [ 22 ] Jones et al . reported a smooth surface architecture of FS-assisted trephined corneas using scanning electron microscopic.…”

Histologic and Ultrastructural Characterization of Corneal Femtosecond Laser Trephination

“…Five years ago, one group studied the alterations induced by a Q-switched erbium YAG laser (nanosecond pulsed laser) during corneal trephination. 25 Light and transmission electron microscopy revealed thermal side effects, which consisted of a carbonization band measuring 1.2 to 6.5 mm wide and a larger coagulation zone with collagen and cellular damage. Recently, a study reported scanning electron microscopy of femtosecond laser trephinations on eye bank eyes showing smooth surface architecture.…”