Femtosecond laser preparation of donor tissue from the endothelial side

The femtosecond laser (Intralase) may provide advantages for dissecting a thin, uniform thickness posterior lamellar disk of donor tissue to be used for endothelial transplantation. We investigated the use of the Intralase to dissect the donor cornea from the posterior side to better obtain a thin and uniform lamellar disk. We investigated the use of a viscoelastic "cushion" to protect the endothelium during applanation and laser delivery.

Human eye bank donor buttons were placed endothelial side up, covered with a thin coat of viscoelastic, and brought into contact with the Intralase applanation lens. A 7-mm diameter, 100-microm lamellar disk was cut from the endothelial side. The endothelial viability after these procedures was determined using a live cell/dead cell assay. Controls were designed to assess the endothelial viability after applanation and laser application using only a balanced salt solution (BSS) cushion instead of viscoelastic material. Additionally, applanation without lasering using either BSS or a viscoelastic cushion was studied.

The average endothelial cell loss in the laser experiment sets were 10% (n = 5, range of 4-17%, Sodium Hyaluronate), 14% (n = 5, range of 7-19%, Sodium Hyaluronate-Sodium Chondroitin) and 6% (n = 5, range of 3-11%, Hydroxypropylmethyl-cellulose). In the controls, laser and applanation with BSS resulted in an average endothelial loss of 18% (n = 5, range of 14-26%). Applanation alone without laser dissection resulted in cell loss of 9% (n = 5, range of 7-12%) using BSS and 9% (n = 6, range 1-42%) Hydroxypropylmethyl-cellulose.

The technique of using a viscoelastic "cushion" to protect endothelial cells from damage during posterior laser dissection prior to transplantation is promising. Viscoelastic coating protects the endothelial layer from damage from the coupling lens better than a layer of BSS. The lasering process, however, causes damage in addition to applanation with the laser lens. Further studies are warranted to optimize reproducibility of endothelial cell survival and evaluate the smoothness of stromal dissections in the posterior cornea.