Baseline, one and three month changes in the peripapillary retinal nerve fiber layer in acute optic neuritis: relation to baseline vision and MRI.

OBJECTIVE Retinal nerve fiber layer (RNFL) loss occurs with MS or after optic neuritis. Acute RNFL alterations at presentation and changes over time have not been well documented. We analyzed regional RNFL changes using 2 methods, ocular coherence tomography (OCT) and scanning laser polarimetry (SLP), to study initial edema and early RNFL loss. METHODS 40 subjects with unilateral acute optic neuritis, had prospective OCT and SLP RNFL thickness values organized into 4 quadrants. We compared affected with normal fellow and control eyes to determine RNFL thickening (≥ 10% of 95th percentile of controls) and thinning (≥ 10μ less than fellow eye) at presentation, 1 and 3 months. RESULTS RNFL thickening occurred in 27/33 eyes (82%) by OCT and in 21/34 eyes (62%) by SLP at baseline. At 1 month, RNFL thickening was common even as thinning developed in 15/23 (65%) of eyes by OCT and in 15/28 eyes (54%) by SLP. At 3 months, RNL was thinned by OCT in 14/24 (58%) and by SLP in 15/25 (60%) affected eyes (58%). Neither MRI optic nerve lesion nor vision at baseline correlated with optical image findings or vision outcome. CONCLUSIONS RNFL swelling, most likely due to axoplasmic stasis from blockade at the lesion site in optic neuritis, is seen with OCT better than SLP. RNFL swelling in some quadrants and loss in others occur at 1 month and is well seen with interocular comparison by both methods. Optical imaging provides pathophysiologic as well as quantitative information regarding axonal changes.