Influence of Standard Corneal Cross-Linking in Keratoconous Patients on Macular Profile

Purpose: Corneal cross-linking to prevent the progression of keratoconus (KCN) has become popular in the last decade. Although different studies indicated it is completely safe if conducted based on the standard protocol, it cannot be accepted decisively, because there is inadequate and limited evidence about the toxic side effects of cross-linking on retina and macula. Methods: study was conducted on 42 eyes of 21 patients with KCN who were the candidates for corneal crosslinking due to the disease progression. The Opto-Vue optical coherence tomography (OCT) from macula and multifocal electroretinography (mERG) were performed for all patients and the patients were followed up with 1 and 6 months intervals after the surgery. The macula parameters such as thickness, and amplitude and latency changes were quantitatively measured before the surgery and in follow-up visits and were compared with those of the opposite eye as the control group. Results: Changes in macula thickness was anatomically assessed in 4 regions of central fovea, fovea, parafovea, and perifovea regions in inner retinal map and a significant thickness increase was observed in the 1- month follow-up, but the trend was not observed in 6-month follow-ups. In macula functional assessments by mfERG, a significant reduction in amplitude and latency increase in rings 2 and 3 were observed in the 1-month follow-up. However, in the 6-month follow-up only amplitude changes in the ring 2 was observed and no changes in the 2 later mentioned parameters were observed in other regions. Conclusion: Anatomical and functional evaluations of the current study showed the transient toxic side effects of cross-linking mostly on the inner retina.