Corneal Stiffening Follows Accelerated Crosslinking Despite Initial Thinning

The accelerated corneal crosslinking (CXL) procedure may alter biomechanical parameters and reveal a corneal stiffening effect in individuals undergoing treatment for progressive keratoconus (KC), according to research published in Cornea. Despite this stiffening, corneal thinning occurred and was most significant at the 1-month follow-up visit, according to the report. 

Researchers enrolled 43 individuals with progressive KC (eyes, 43) and included untreated fellow eyes (n=25) as controls in an investigation conducted at a single center between November 2017 and December 2019.  Participants underwent biomechanical assessment using Scheimpflug-based tonometry and tomographic measurements at baseline and during 1-, 6-, and 12-month follow-up visits. The team compared biomechanical parameter alterations between treated and untreated eyes. 

Central corneal flattening occurred following accelerated CXL, evidenced by a 1.1 diopter (D; 95% CI, -2 to -1; P =.025) maximum keratometry (Kmax) decrease at 12 months compared with baseline. Thinnest corneal thickness values revealed significant corneal thinning at the 1-month postoperative visit compared with baseline (449 vs 463 µm; P <.001), but these values recovered to preprocedural levels at 12 months (P =.752). Biomechanically-corrected intraocular pressure (bIOP) increased (14.8 vs 13.3; P =.002), the time to second applanation shortened (22.06 vs 22.27 m/s; P =.024), and integrated radius values were lower at the 1-month follow-up compared with baseline. The eyes used in the control analysis did not experience any significant changes in biomechanical or tomographic parameters, the report shows. 

“[T]he alterations in biomechanical parameters indicated a corneal stiffening effect after CXL treatment, which was best detectable 1 month after treatment, although [central thickness] was reduced,” according to the researchers. “However, a higher severity of KC seems to benefit from a higher cross-linking effect.”

Study limitations include a single center design and failure to assess non accelerated CXL protocols.