Experimental application of 1% hydroxypropylmethylcellulose for corneal endothelium protection during inverted posterior lamellar corneal graft preparation technique by low-energy femtosecond laser

Abstract

Purpose. To evaluate experimentally endothelial cell loss of animal's cornea during inverted posterior lamellar corneal graft preparation technique by low-energy femtosecond laser with and without ophthalmic viscosurgical device (OVD) – 1% hydroxypropyl methylcellulose (HPMC) solution application. Material and methods. Posterior lamellar corneal grafts were created using a femtosecond laser (FSL). In the control group (n=16), a few drops of corneal storage solution were applied to the endothelium just before applanation, in the experimental group (n=16) – 1% HPMС. The quality of the applanation were monitored using an integrated in laser OCT system. The endothelial viability was determined using live/dead cells assay and the grafts were examined on a confocal laser scanning microscope. The obtained images were analyzed to count live and dead endothelial cells (EC). To assess the state of collagen fibers of the stromal side of the graft, samples from the control and experimental groups were examined using a scanning electron microscope (SEM). Results. According to the OCT, in all samples of both groups, a flat profile of the contact zone between the laser head and the endothelial monolayer was observed during applanation. The difference between the number of live and dead ECs was statistically significant between both groups. There were 2854 [2819; 2879] live cells/mm² in the control group, and 3477 [3426; 3719] live cells/mm² in the experimental group (p<0.001). Thus, the number of dead ECs in the control group was 710 [649; 728] cells/mm² . The number of dead ECs in the experimental group was 402 [366; 427] cells/mm² (p<0.001). When analyzing the images obtained on a SEM, the preservation of the architectonics of the graft collagen fibers with their single defibrations in both groups was observed. Conclusion. Application of 1% HPMC provides protection for endothelial cells from damage during posterior laser dissection using an FSL. In the study group, the number of endothelial cells was 9.92% higher than in the control group. The presence of the OVD layer in the interface between the head of the FSL and the EC did not affect the formation of an effective laser cut and did not reduce the quality of the stromal surface of the graft. The inverted technique FSL cut using a 1% solution of HPMC on the surface of the endothelium may be recommended for use in clinical practice. Key words: endothelium, keratocytes, corneal transplantation, keratoplasty, posterior lamellar keratoplasty, femtosecond laser, ophthalmic viscosurgical device, hydroxypropyl methylcellulose, confocal microscopy, scanning electron microscopy