Purpose The peripapillary retinal nerve fiber layer (pRNFL) and the macular ganglion cellinner plexiform layer (GCIPL) are important predictive factors for the prognosis of optic neuritis (ON). We investigated the risk factors for pRNFL and GCIPL thinning in ON and its relationship with visual function. Patients and methods We analyzed 33 eyes of 33 patients with a first attack of unilateral ON. Patients were divided into two groups according to pRNFL and GCIPL thinning, using spectral-domain optical coherence tomography. We evaluated patients' age, sex, color vision, visual acuity (VA), optic nerve findings on MRI, elapsed period from onset of visual symptoms to steroid treatment, visual field (VF) mean deviation (MD), average pRNFL thickness, and GCIPL thickness. Results There was no patient with residual VF defect in the groups without pRNFL or GCIPL thinning. Significant correlations were found between pRNFL (some sectors) and GCIPL (all sectors) thickness and BCVA and VF MD (Po0.03 for all). Multivariate logistic regression analysis revealed that only worse initial VF MD was a significant risk factor of pRFNL and GCIPL thinning after ON (OR, 0.841; 95% CI, P = 0.017 and OR, 0.871; 95% CI, P = 0.046, respectively). Conclusion Retinal ganglion cell and axonal losses occurred in ON cases showing severe initial VF loss. Therefore, it is necessary to pay more attention to the degree of initial VF loss in ON while considering the possibility of residual VF loss accompanying pRNFL and GCIPL thinning.