Abstract
Purpose :
Low density plasma generated reactive oxygen species (ROS) have been used to crosslink corneal collagen with exacting femtosecond laser pulse parameters. We hypothesize that by increasing the cornea’s optical absorbance through melanin application, ROS can be produced from a denser plasma, leading to robust trans-epithelial corneal crosslinking therapies for keratoconus and vision correction.
Methods :
Fresh rabbit eyes were enucleated, exposed to 1% w/w melanin dissolved in PBS, and divided into groups A, B, C, and D (n=3 each). A and C had their epithelium-removed with a scalpel before femtosecond laser irradiation at 1060nm with 100mW, whereas B and D maintained intact epithelium before 185mW irradiation. For group A and B rabbit eyes, effective refractive power (Eff.RP) was assessed with topography, and corneal apical thickness was monitored with optical coherence tomography (OCT) on eyeballs kept with 18-20mm H2O intraocular pressure over a 10-hr period. For group C and D corneas, 5um radius nanoindentations were performed on 3mm diameter corneal buttons after laser treatment. All laser-scanned corneas were mechanically loaded with a coverslip. Paired controls were exposed to melanin but received no light irradiation.
Results :
Over the 10-hr period, the Eff.RP significantly decreased 7.47 diopters for epithelium-removed eyes (A: p<0.01) and 4.67 diopters for epithelium-intact (B: p<0.05) eyes after melanin-assisted laser crosslinking. The equilibrium modulus of crosslinked tissues significantly increased to 80kPa for epithelium-removed corneas (C: p<0.05) and 33kPa for epithelium-intact corneas (D: p<0.005), while paired controls were approximately 10kPa (Fig. 1). However, there was no difference in the apical corneal thickness change between treated and control eyes (A: p=0.883; B: P=0.622, Fig. 2).
Conclusions :
Melanin-assisted, femtosecond laser ROS crosslinking generated significant corneal stiffening and stable refractive power decrease with and without epithelium, proving its potential for transepithelial keratoconus and myopia treatment. Though the treatment regime at the chosen power levels did not cause notable stromal edema, further morphological examinations and long-term in vivo experiments are needed to understand the safety and stability of plasma-cornea interaction yielded effects.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.