Strength properties of rabbit cornea after femtosecond laser keratoplasty with and without different intracorneal implants

Abstract

to conduct a comparative experimental study of the effect of the use of intracorneal implants during femtosecond laser-assisted intrastromal pocket (IP) and intrastromal tunnel (IT) formation on the strength properties of the cornea. The experimental study was performed on 24 corneas of 12 rabbit eyes enucleated 1 month after slaughtering. All eyes were divided into 6 groups according to the method of operation. IP and IT were created with IntraLase FS 60 kHz femtolaser. Group 1 (control group) consisted of rabbit eyes with intact corneas. In group 2 corneas, intrastromal tunnels were formed, in group 3 - intrastromal pockets, and in group 4 - intrastromal tunnels with 2 intracorneal segments (ICS). In groups 5 and 6, intrastromal pockets, each supplemented with an intrastromal ring, were created at the depth of 62-72% and 80% of pachymetry readings from the 5.0-mm optical zone, respectively. Higher voltage had to be applied to stretch the samples from group 2 as compared to those from groups 3 and 6. Distribution of the Young's modulus of the test corneas agreed with voltage distribution in the study groups. IP was associated with greater reduction in corneal biomechanical stability as compared with IT. Ring implantation into an IP yielded a more pronounced increase in the strength properties of the cornea than ICS implantation into an IT. The result was also more favorable at greater depths of intrastromal ring implantation.