Comparison of Corneal Collagen Cross-Linking Protocols Measured With Scheimpflug Tomography

To evaluate the effectiveness of corneal collagen cross-linking with Dresden and accelerated protocols to treat keratoconus by Scheimpflug tomography.

Fifty-eight eyes with manifest keratoconus were measured preoperatively at least twice with the Pentacam. The difference of relevant variables for keratoconus progression (eg, D value, thinnest pachymetry, Kmax) was established. After evident progression, patients underwent corneal cross-linking (29 eyes with the Dresden protocol and 29 eyes with the accelerated protocol). Postoperatively, variables used for defining manifest progression were compared again by measuring the difference between 2 measurements.

Preoperatively, the mean D value was 9.6 ± 4.8 for the Dresden cohort and 8.3 ± 5.1 for the accelerated cohort. There was no significant difference between both cohorts in terms of the mean preoperative difference in the D value (0.59 ± 1.7 for the Dresden cohort vs. 0.4 ± 1.49, P = 1). Postoperatively, however, a significant difference (P < 0.01 for the accelerated corhort) was found (Dresden: -0.47 ± 0.88 vs. accelerated: 0.04 ± 0.67). Regression analysis showed that keratoconus progression was significant in both study groups preoperatively (with a significant reduction of corneal thickness and increase in the D value). Postoperative data show an improvement in all observed keratoconus indices in both study groups and stagnation in progression for the accelerated cohort, P = 0.774, for the D value and a regression in manifestation for the Dresden cohort (decrease in the D value, P < 0.01).

Before operative intervention, Scheimpflug imaging showed signs of a progressive disease in all eyes. Both conventional Dresden protocol and accelerated pulsed corneal collagen cross-linking techniques effectively stopped this progression.