Correlation of central and peripheral keratometric parameters after corneal collagen cross-linking in keratoconus patients

Purpose: To evaluate the difference in the central and peripheral keratometric parameters in patients with keratoconus after corneal collagen cross-linking (CXL). Methods: Forty-eight eyes of 32 patients (18 males, 16–28 years) affected by progressive keratoconus in different stages of evolution underwent CXL using the standard epithelium-off protocol. Corneal thickness and corneal curvature before CXL and after 6 and 12 months using the Sirius tomographer were analyzed. The values of the mean corneal thickness at the corneal apex (CAT), center of the pupil (PCT), thinnest point (CTTL) and along concentric circles of 2, 4, 6, 8, 8.5, 9, 9.5 and 10 mm diameter were evaluated; the values of the mean curvature at the corneal apex and at the points in which the inferior, superior, nasal and temporal meridians crossed the above-mentioned concentric circles were also evaluated. Results: The mean preoperative values for CAT, PCT and CTTL were 461.4 ± 30.3, 475.3 ± 30.5 and 441 ± 32.0, respectively. The values after 12 months of CXL were 444.6 ± 36.2, 451.6 ± 36.7 and 418.2 ± 41.4. The peripheral corneal thickness at the eight points ranged from 479 to 733 preoperatively. At 12-month post-CXL, the values ranged from 444.6 to 734.1. The mean posterior curvature from apex to periphery ranged from − 4.5 to − 9.1 days preoperatively and from − 4.5 to − 9.2 days at 12 months. These were not statistically significant (ANOVA and unpaired T test). Conclusions: Our data suggest that CXL over an 8-mm zone can stabilize the peripheral cornea. Longer-term follow-up studies on the peripheral cornea after CXL will provide useful information.