Corneal topography important to monitor after CXL

July 9, 2014

When performing corneal collagen crosslinking (CXL), ophthalmologists should monitor the keratoconus index and the index of height asymmetry garnered from the Scheimpflug camera, because changes in values of these indices are independent from initial corneal thickness.

When performing corneal collagen crosslinking (CXL), ophthalmologists should monitor the keratoconus index and the index of height asymmetry garnered from the Scheimpflug camera, because changes in values of these indices are independent from initial corneal thickness. So say researchers from Hungary publishing their work in the Journal of Refractive Surgery.

The researchers, from Hungary, performed CXL in 25 eyes with progressive keratoconus; 25 fellow eyes with nonprogressive keratoconus were the control subjects. The Scheimpflug camera was used to measure thinnest corneal thickness, anterior keratometry (flat, steep) and keratoconus indices before and after CXL (at 12 to 25 months). They assessed the influence of corneal thickness and follow-up time on the flattening effect of CXL using regression analysis.

The investigators found that, at baseline, the eyes that had undergone CXL had significantly higher steep keratometric values and lower thinnest corneal thickness values. These findings were parallel with increased values of the following keratoconus indices: index of surface variance, index of vertical asymmetry, keratoconus index, centre keratoconus index, index of height asymmetry, index of height decentration and radius minimum.

After they adjusted for thinnest corneal thickness and follow-up time, the researchers found that a significant flattening effect was shown with CXL; it was expressed by changes in radius minimum, index of surface variance, keratoconus index, center keratoconus index and index of height asymmetry. Changes of index of surface variance, index of vertical asymmetry and center keratoconus index were significantly influenced by thinnest corneal thickness. Follow-up time had no significant influence in any of the models studied.

To read an abstract of the study, visit the journal's website.