Six-month longitudinal analysis of visual, tomographic, and densitometric changes after corneal collagen cross-linking in keratoconus

Abstract Background: Keratoconus is a progressive corneal ectasia commonly treated with corneal collagen cross-linking (CXL) to halt further progression. Although transient anterior stromal haze frequently develops after CXL, its impact on visual recovery remains unclear. This study aimed to examine the correlation between postoperative changes in corneal densitometry, visual acuity, topography, and pachymetry in eyes with keratoconus undergoing CXL. Methods: This retrospective study included eyes with progressive keratoconus undergoing epithelium-off accelerated CXL. Pre- and postoperative assessments included measuring corrected distance visual acuity (CDVA), manifest refraction, and slit-lamp biomicroscopy examination, along with Pentacam HR imaging. Densitometry was quantified across three stromal depths and four annular zones. Follow-up evaluations were performed at day ۱, week ۱, and months ۱, ۳, and ۶ post-CXL. Results: Twenty-four eyes from ۲۴ patients with progressive keratoconus (median age, ۲۱.۹ years; ۷۹.۲% male) were evaluated over a six-month period following CXL. At six months significant improvements were observed in CDVA, accompanied by reductions in flat keratometry, central corneal thickness, and thinnest pachymetry (all P < ۰.۰۵). Corneal densitometry increased significantly at one month and partially regressed by six months across all stromal depths and within all concentric annular zones from ۰.۰–۲.۰ mm to ۶.۰–۱۰.۰ mm and their corresponding total values (all P < ۰.۰۵). Baseline anterior ۰.۰–۲.۰ mm densitometry demonstrated a significant inverse correlation with CDVA (r = –۰.۵۰, P < ۰.۰۵). At one month, CDVA correlated inversely with anterior (r = –۰.۴۷, P = ۰.۰۰۳) and mid-stromal (r = –۰.۵۸, P = ۰.۰۰۶) ۰.۰–۲.۰ mm densitometry, and with anterior ۲.۰–۶.۰ mm densitometry (r = –۰.۴۵, P = ۰.۰۴۵). By six months, no significant correlations were found between CDVA or absolute keratometric parameters and densitometry at any depth, zone, or total value (all P > ۰.۰۵), indicating stabilization of both visual and structural recovery. Conclusions: Accelerated epithelium-off CXL yielded significant visual and structural improvements in progressive keratoconus over six months. Corneal densitometry followed a characteristic postoperative pattern, with an early peak at one month followed by partial regression. Early stromal backscatter increases were significantly correlated with visual acuity, but these relationships diminished by six months, consistent with recovery of corneal clarity and vision. Longer-term studies are warranted to clarify the prognostic utility of densitometry for visual and tomographic outcomes after CXL. Keywords: keratoconus pellucid marginal degeneration densitometries light scattering corneas corneal stromas corneal topographies vitamin B۲ riboflavin epithelium-off CXL