Femtosecond laser-assisted procedure latest advance in endothelial keratoplasty

May 7, 2007

Rapid advances in technology and improved ablation algorithms for the femtosecond laser have enabled its use to dissect the donor corneal lamellae for Descemet's stripping automated endothelial keratoplasty (DSAEK), said Donald Tan, MD, professor of ophthalmology, National University of Singapore.

Rapid advances in technology and improved ablation algorithms for the femtosecond laser have enabled its use to dissect the donor corneal lamellae for Descemet's stripping automated endothelial keratoplasty (DSAEK), said Donald Tan, MD, professor of ophthalmology, National University of Singapore.

Dr. Tan presented results from an investigation performed to assess the quality of donor tissue dissected using a prototype 40-Hz femtosecond laser (Femtec, 20/10 Perfect Vision). The study used human research grade corneoscleral rims mounted on an artificial anterior chamber and compared the quality of the vertical and horizontal lamellar cuts after single, double, or triple lamellar ablation passes. Evaluations were made on tissues fixed and processed for scanning electron microscopy (SEM).

Two masked independent observers graded the SEM images using a four-point scale developed from reference images. The results showed the double-pass technique provided a very smooth ablation with a significantly better stromal bed quality score compared with both the single- and triple-pass techniques. The stromal bed and rim cut qualities achieved with the double-pass technique were considered at least as good as those associated with use of a mechanical microkeratome. In addition, only mild collateral damage to the adjacent endothelium was noted with these dissections performed at 150 µm from Descemet's membrane. When the donor tissue was placed in the modified Hanna suction trephine block after the double-pass ablation, the graft was readily peelable with a forceps.

"The current method of donor preparation for DSAEK using microkeratome-assisted lamellar dissection and the ALTK unit (Moria) works well and yields good clinical results," Dr. Tan said. "However, some problems can occur, including variations in cap diameter and thickness.

"We feel this particular laser is ideal for deep lamellar dissection because it has a curved interface that, unlike other lasers, allows for minimal corneal distortion or compression," Dr. Tan said. "We believe femtosecond laser-assisted endothelial keratoplasty represents the latest development in the evolution of endothelial keratoplasty."