In this trial, the investigators, led by Lional Raj Daniel Raj Ponniah, MD, the investigators aimed to compare the two treatment options and prove the concept that deeper stromal crosslinking has a more significant effect on inhibiting the progression of keratoconus.
The phase 1 prospective, non-randomized clinical trial enrolled 21 patients into the conventional treatment group and 25 patients into the Femto assisted crosslinking (CXL) group at Dr. Agarwal’s Eye Hospitals in Tirunelveli, South India.
Eligible participants were required to be between the ages of 15 and 30, to have progressive keratoconus with the “thinnest pachymetry over 400 microns” and a specular endothelial cell density of more than 2000 cells per mm2.
In the conventional treatment group, the investigators' methods consisted of an epi-off procedure with Dresden protocol of 2mW per cm2.
The method used in the femtosecond CXL group included 2 incisions of 180 degrees apart with femto lasers into a stromal bed (140 to 160 microns deep, 8.5 to 9.0 mm in diameter). Then, infusions were conducted ever 5 minutes with isotonic riboflavin 0,1% w/v in addition to a transepithelial application every 2 minutes for 25 minutes followed by UV irradiance for 20 minutes. Finally, the stromal bed was washed with a balanced salt solution.
The Phase 1 results indicate that uncorrected visual activity (UCVA) was improved by 2 lines and 1 line in femto-CXL and conventional-CXL respectively (p=0.005). Additionally, the best corrected visual activity (BCVA) improvement was reported to be similar as well.
The minimal central pachymetry was maintained in femto-CXL and reduced by 25 microns (p<0.05) in conventional-CXL. Furthermore, patients in the femto-CXL had a more favorable outcome in the retention of corneal thickness (p=0.01).
The investigators also report that crosslinking flattened corneas in both the femto-CXl treatment group and the conventional treatment group. Astigmatism was reduced in the femto-CXL group by 0.22 Diopters and increased by 0.27 D in the conventional-CXL group.
According to the data, there were no endothelial changes noted in either treatment groups in the categories of cell density, coefficient of variance, and hexagonality.
The investigators conclude that “crosslinking the posterior corneal stroma deeper than 250 microns could be achieved with femto laser assisted CXL than conventional procedures, favoring an effective stabilization of keratoconus in terms of preventing steepening and further thinning of cornea, as proof of deeper the better concept.”
In a follow-up of 24 of the patients from the femto-CXL group, the investigators indicate that clinical stability was absorbed in the corneas of the patients and no progression in thinning was observed after 2 years.