AIM: To describe the optical coherence tomography (OCT) features in the fellow eyes of individuals with full-thickness macular holes (FTMHs). METHODS: This multicenter retrospective study included observational and validation groups, incorporating fellow eyes of patients diagnosed with idiopathic FTMH. OCT images were categorized according to International Vitreomacular Traction Study (IVTS) and Gass classification. Age- and sex-related cataract patients were served as control groups. Vertical and horizontal OCT images were chosen for further measurement. OCT parameters including foveal floor width (FFW), central foveal thickness (CFT) and FFW/CFT ratio were assessed and compared between observational and control groups and were validated by validation group. Receiver operating characteristic (ROC) curves were plotted for OCT parameters in identifying macular holes (MHs). RESULTS: A total of 73 patients were included in the observational group, comprising 51 females and 22 males, with an average age of 65.5±7.3y and an axial length of 23.9±0.8 mm. The validated group consisted of 47 patients, including 31 females and 16 males, with an average age of 65.0±7.4y and an average axial length of 23.6±0.8 mm. In the observational group, 16.4% of the fellow eyes associated with FTMHs also exhibited MHs, while in the validated group, this prevalence was 12.7%. The 45.2% in the observational group and 44.6% in validated group of these fellow eyes displayed abnormalities including vitreomacular adhesion (VMA), vitreomacular traction (VMT), and MHs. Statistically significant differences were observed in FFW, CFT, and FFW/CFT ratio between control and observational group, as well as validated group (P<0.01), no matter in the vertical or horizontal layer. ROC curves revealed the area under the curve (AUC) for FFW and the FFW/CFT ratio was 0.85 and 0.90, respectively. CONCLUSION: In the case of unilateral idiopathic MHs, it was important to carefully monitor the condition of the fellow eye. The FFW and FFW/CFT ratio may be good metrics for predicting MHs.