Background In this prospective case series, we aimed to characterise the temporal evolution of functional and structural measures in the afferent visual pathway of patients with acute optic neuritis (ON).

Methods Fifty patients with ON were followed over 12 months. Testing with spectral-domain optical coherence tomography, Early Treatment Diabetic Retinopathy Study logarithm of the minimum angle of resolution (LogMAR) visual acuity and Humphrey perimetry central 30-2 threshold (SITA strategy) was performed at baseline, 3, 6 and 12 months after symptom onset. The main outcome measure was mean peripapillary retinal nerve fibre layer (RNFL) thickness in ON eyes. Secondary outcomes included mean ganglion cell layer (GCL) thickness, LogMAR visual acuity, and Humphrey perimetry measured visual field mean deviation (VFMD). Survival analyses were performed to Kaplan-Meier curves and variables in the models were tested using the log-rank test.

Results Over 12 months, RNFL and GCL values progressively declined in ON eyes, and intereye differences were significantly different across all time points. When functional recovery was defined as a VFMD better than −5.00 dB in ON eyes, the mean recovery time for the entire cohort was 3 months (survival was 48%, SE=0.09, 95% CI 0.30 to 0.64). There were significant differences in cumulative recovery when comparisons were made between genders: 3 months after symptom onset there was a higher percentage cumulative recovery for female (75%) versus male (25%) patients.

Conclusions Structural and functional measures evolve over time in patients with ON. There may be sex-specific differences in recovery after an acute ON event.