Keratoconus causes irregular astigmatism and reduced vision. Epi-off corneal crosslinking (CXL) stabilizes the cornea but often leaves higher-order aberrations uncorrected. This randomized, parallel-group trial compares corneal wavefront guided photorefractive keratectomy (corneal wavefront guided PRK, 50 µm therapeutic ablation) combined with accelerated epi-off CXL versus epi-off CXL with epithelial removal by phototherapeutic keratectomy (PTK) using a Schwind AMARIS excimer laser, in adults with keratoconus. The primary endpoint is change in best-corrected distance visual acuity (logMAR) at 12 months. Key secondary endpoints include Kmax, corneal higher-order aberrations, manifest refraction, Scheimpflug densitometry (haze) and Fantes grade, Corvis ST biomechanics, NEI VFQ-25, and endothelial cell density by non-contact specular microscopy at 1, 3, 6 and 12 months.
Age 18-40 years
Diagnosis of keratoconus, ABCD Belin stage I-III at baseline
Minimum (thinnest) corneal pachymetry ≥ 450 µm pre-op
Written informed consent
Central corneal scars or opacities
Prior ocular surgery or trauma (exception: prior LASIK if it is the cause of post-surgical ectasia, per protocol text)
Autoimmune disease or uncontrolled diabetes mellitus
Pregnancy or lactation
Parallel
Schwind AMARIS excimer laser
DeviceUsed for corneal wavefront guided PRK therapeutic ablation (50 µm) or for PTK epithelial removal, according to arm assignment.
Corneal collagen crosslinking epi-off accelerated
Procedure/SurgeryRiboflavin-UVA crosslinking performed after epithelial removal (corneal wavefront guided PRK arm via PRK; comparator arm via PTK). Intensity: 30 mW/cm² (pulsed 1 s on / 1 s off; 50% duty cycle). Total energy (fluence): 5.4 J/cm². Total time (elapsed): 6 minutes \[equivalent to 3 minutes "on" time\].
Change in best-corrected distance visual acuity (logMAR)
ETDRS-based CDVA in logMAR; change from baseline at 12 months; primary analysis by ANCOVA adjusted for baseline; one study eye per participant.
Change in Kmax (Diopters)
Pentacam Scheimpflug tomography; maximum keratometry (D); change from baseline at each time point.
Change in corneal higher-order aberrations (µm RMS)
Wavefront/aberrometry total HOAs RMS (µm) over 6-mm pupil; change from baseline.
Change in manifest refraction spherical equivalent (Diopters)
Manifest refraction SE (D); change from baseline.
Corneal haze (Scheimpflug densitometry units)
CCT and corneal haze as measured by Pentacam Corneal Densitometry. Unit of measure: gray units.
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