Corneal transparency after cross-linking for keratoconus: 1-year follow-up

To evaluate the changes in corneal transparency and thickness measured objectively using Pentacam Scheimpflug (Oculus Optikgeräte GmbH) corneal tomography (densitometry) after corneal cross-linking (CXL).

Twenty-two eyes from 15 patients with keratoconus underwent CXL. Corneal thickness and curvature as well as lens and corneal densitometry were measured at baseline and 1, 3, 6, and 12 months after CXL with Pentacam.

Immediately after CXL, central corneal thickness significantly decreased (-40 μm) and corneal densitometry increased significantly. At 6-month follow-up, densitometry values were reduced and seemed to stabilize at a higher value than baseline. No statistically significant differences were noted (mean difference at 12 months: +30%). Changes in corneal densitometry were detected with the Pentacam even when clinical haze did not increase beyond grade 1 during follow-up.

Corneal CXL is associated with a transient reduction in central corneal thickness, which recovered to baseline after 12 months. During the same time period, corneal densitometry experienced a transient increase that recovered to baseline values after 3 months. Changes in compactness of the corneal tissue after CXL may have an impact in corneal power not due to curvature changes, but to refractive index changes as a result of hydration changes. Pentacam is a useful objective method to monitor corneal transparency after CXL.