Keratoconus patients with fewer HOAs post-CXL had improved binocular performance.
Keratoconus patients with fewer HOAs post-CXL had improved binocular performance. Photo: Nurit Wilkins, OD. Click image to enlarge.

Higher-order aberrations (HOAs) have been demonstrated to profoundly affect both visual acuity and stereoacuity in patients with keratoconus. Corneal collagen crosslinking (CXL) has been proven to significantly lower HOAs in keratoconus. Yet, to the present date, no evaluation of the effect of the procedure on stereopsis has been performed. A recent study assessed differences in binocular visual performance in patients with keratoconus before and after CXL, finding that this cohort showed a reduction in HOAs and significant improvement in stereoacuity post-treatment.

The study included 30 patients with keratoconus undergoing the standard Dresden epi-off CXL protocol. All underwent slit lamp examination, uncorrected and corrected distance visual acuity assessment, corneal tomography, Lang stereo testing, TNO stereoacuity assessment, distance and near cover testing and Irvine testing before and six months after CXL.

The Lang test improved after treatment, with 20% of patients showing a positive result before CXL compared with 53% after. Moreover, TNO stereoacuity increased after treatment, with 47% manifesting an improvement of at least 250” post-CXL. In this subgroup of patients, total root mean square values decreased after treatment, whereas patients who did not manifest a clinically significant improvement in stereoacuity did not show a reduction. The results of cover testing and Irvine testing did not vary before and after CXL.

“We hypothesize that the reduction in HOAs could provide a significant contribution to the improvement in binocular performance of patients with keratoconus,” the study authors concluded in their paper. “Further studies will be needed to strengthen the evidence on the subject, verify the effect of different CXL protocols on the same outcomes and possibly define a subgroup of patients with keratoconus benefiting the most from HOA variations due to CXL.”

Fasciani R, Crincoli E, Fedeli C, et al. Binocular visual function changes after corneal collagen cross-linking in patients with keratoconus. Cornea. May 13, 2022. [Epub ahead of print].