Changes in Corneal Density After Accelerated Corneal Collagen Cross-linking With Different Irradiation Intensities and Energy Exposures: 1-Year Follow-up

Purpose: To determine and compare the changes in corneal density after 2 different protocols of accelerated corneal collagen cross-linking (A-CXL) in patients with progressive keratoconus. Methods: Two groups of eyes received A-CXL treatment; 20 eyes received A-CXL using continuous UVA light exposure at 9 mW/cm(2) for 10 minutes with a total energy dose of 5.4 J/cm(2), and 24 eyes received A-CXL using continuous UVA light exposure at 30 mW/cm(2) for 4 minutes with a total energy dose of 7.2 J/cm(2). Corneal density was measured with Scheimpflug tomography at 1, 3, 6, and 12 months of follow-up. Results: Densitometry peaked at 1 month (mean: 16.34 +/- 3.80, P = 0.006, 9-mW/cm(2) A-CXL; mean: 20.90+/-2.81, P < 0.0001, 30-mw/cm(2) A-CXL) in both groups, and it decreased over time in 30-mW/cm(2) A-CXL. However, in 9-mW/cm(2) A-CXL, increased corneal densitometry plateaued until 6 months postoperatively and started to decrease thereafter. Densitometry completely returned to baseline after 12 months in both groups. The mean change in density at 1- and 3-month follow-up was higher in the 30-mW A-CXL group than in the 9-mW A-CXL group (P = 0.003, P = 0.044; respectively). Conclusions: High-energy exposure tends to induce more haze in the early posttreatment period, but it is reversible.