Akçay, EmineEnsari Delioglu, Ezgi NazKars, Meltem EceDemir, PervinÇağıl, Nurullah2025-02-172025-02-172023-10-200004-2749https://hdl.handle.net/11693/116313###### **Purpose:** This study aimed to examine the effects of unilateral corneal collagen cross-linking treatment on visual acuity and the topographic findings of the fellow untreated eye of patients who had bilateral progressive keratoconus. ###### **Methods:** Patients with progressive keratoconus who underwent cross-linking treatment were screened retrospectively. A total of 188 untreated eyes of 188 patients whose eyes were treated unilaterally with either standard or accelerated cross-linking and refused cross-linking procedure for the fellow eye were included. Visual acuity and topographic findings of the fellow untreated eyes were obtained preoperatively and postoperatively at the 1^st, 3^rd, 6^th, 12^th, 24^th, 30^th, and 36^th months. ###### **Results:** The change over time of variables examined was similar in the untreated eyes of patients who received standard and accelerated cross-linking methods (p>0.05). At the 12th month, 136 (95.8%) untreated eyes were stable according to progression criteria. Only 4 (8%) eyes were progressive at the 24th month. No progression was observed in any of the 16 patients with a 36-month follow up. ###### **Conclusions:** The results showed that the fellow untreated eyes of patients with bilateral progressive keratoconus did not have significant progression rates after unilateral cross-linking treatment.EnglishCC BY 4.0 (Attribution 4.0 International Deed)https://creativecommons.org/licenses/by/4.0/Corneal topographyCross-linking reagentsKeratoconusPhotosensitizing agentsCollagen/therapeutic usePhotochemotherapyVisual acuityArticle10.5935/0004-2749.2022-00041678-2925