Abstract
Purpose:
To evaluate the 5-year safety and efficacy of the ELZA-sub400 protocol, an individualized stromal thickness–guided corneal cross-linking (CXL) technique, in eyes with progressive keratoconus and corneal stroma thickness of less than 400 µm.
Methods:
In this retrospective interventional case series, 39 eyes of 33 patients with progressive keratoconus or primary ectasia and stromal thickness between 214 and 398 µm underwent CXL using the ELZA-sub400 protocol. Following epithelial removal and riboflavin loading, ultraviolet-A irradiation at 3 mW/cm
2
was applied for durations tailored to stromal thickness, targeting a demarcation line (DL) 70 µm anterior to the corneal endothelium. Outcome measures included anterior radius of curvature over the central 3 mm (ARC3mm), maximum keratometry (Kmax), corrected distance visual acuity (CDVA), refractive error, stromal thickness, and corneal densitometry, assessed by Scheimpflug tomography (Pentacam HR; Oculus Optikgeräte GmbH) annually for 5 years. Mean follow-up was 3.6 ± 1.5 years (range: 1 to 5 years), with 18 of 39 eyes (46.2%) completing the 5-year follow-up.
Results:
At 5 years after CXL, 84.6% of eyes (33/39) remained stable or flattened (Kmax change ≤1.00 diopters [D]). Kmax decreased significantly from baseline (mean: −2.74 ± 2.65 D,
P
P
= .014). Median CDVA was unchanged (0.40 logMAR,
P
= .572). No significant change was observed in spherical (
P
= .211) or cylindrical (
P
= .280) refractive error. DL depth averaged 275 ± 61 µm; no endothelial decompensation occurred. Minimum corneal thickness declined modestly (median −10 µm,
P
= .049). Anterior densitometry increased slightly (+2.40 grayscale units,
P
= .007), remaining within mild clinical ranges.
Conclusions:
The ELZA-sub400 protocol safely stabilized keratoconus in 84.6% of ultrathin corneas over 5 years, with no signs of endothelial damage. Individualized fluence enabled effective treatment of corneas previously ineligible for standard CXL.