Abstract
Purpose:
We recently introduced corneal crosslinking using Rose Bengal (RB) and green light as a potential treatment (called RGX) for keratoconus especially for patients with thin corneas. We have demonstrated that RGX treatment conditions that increased cornea stiffness did not elicit detectable damage to the retina or iris. This study was designed to further characterize RGX for clinical use by investigating a higher light fluence and longer observation time.
Methods:
Corneas of Dutch belted rabbits (n=8) were de-epithelialized, then stained with RB (0.1% in PBS) for 2 min in an 11 mm circle. This area was exposed, using a limbal shield, to green laser light (532 nm, 0.25 W/cm2) for a total of 9.9 min during which time RB was reapplied after 3.3 and 6.6 min. Contralateral control corneas were de-epithelialized but not further treated. On Day 28 Sstiffness at 10% extension was measured on day 28 by uniaxial tensiometry on 2-mm cornea strips and central corneas thickness was measured. The area of re-epithelialization was quantitatively assessed from fluorescein fluorescence images. A smaller group of rabbits (n=3) received the same treatment and measurements were made on Day 1. RB remaining in the cornea was assessed by spectrophotometry. Student’s t-test for paired data was used to test for significance.
Results:
RGX-treated corneas showed 2.8-fold greater stiffness than control corneas 28 days after treatment (4.95±1.85 vs 1.76 ± 0.70 N/mm; p<0.01). Cornea thickness was slightly, but not significantly, greater for RGX-treated than controls. The re-epithelialization rates for RGX-treated and control corneas did not differ; percent re-epithelialization after 7, 14, 21 and 27 days were was 70±13, 80±10, 92±8 and 98±5 %, respectively. Three rabbits showed infections in the RGX-treated eyes that were treated with antibiotics. On Day 1, the stiffness of RGX-treated corneas (2.38±0.59 N/mm) was 1.8-fold greater than controls (1.25±0.21 N/mm); p=0.001) but lower than on Day 28. Less than 5% of RB remained in RGX-treated corneas, which appeared very slightly pink.
Conclusions:
These results demonstrate that RGX produces substantial increases in cornea stiffness and that even high fluence of green light fluences does not delay cornea re-epithelialization. Taken together with the previously demonstrated lack absence of damage to retina and iris suggests that RGX is a promising treatment for keratoconus and other ectatic conditions.