Optical coherence tomography is less sensitive than visual evoked potentials in optic neuritis

Abstract

Objectives: Determine the utility of optical coherence tomography (OCT) to detect clinical and subclinical remote optic neuritis (ON), its relationship to clinical characteristics of ON and visual function, and whether the retinal nerve fiber layer (RNFL) thickness functions as a surrogate marker of global disease severity.

Methods: Cross-sectional study of 65 subjects with at least 1 clinical ON episode at least 6 months prior. Measures included clinical characteristics, visual acuity (VA), contrast sensitivity (CS), OCT, and visual evoked potentials (VEP).

Results: Ninety-six clinically affected optic nerves were studied. The sensitivity of OCT RNFL after ON was 60%, decreasing further with mild onset and good recovery. VEP sensitivity was superior at 81% (p = 0.002). Subclinical ON in the unaffected eye was present in 32%. VEP identified 75% of all subclinically affected eyes, and OCT identified <20%. RNFL thickness demonstrated linear correlations with VA (r = 0.65) and CS (r = 0.72) but was unable to distinguish visual categories <20/50. RNFL was thinner with severe onset and disease recurrence but was unaffected by IV glucocorticoids. OCT measurements were not related to overall disability, ethnicity, sex, or age at onset. The greatest predictor for RNFL in the unaffected eye was the RNFL in the fellow affected eye.

Conclusions: Visual evoked potentials (VEP) remains the preferred test for detecting clinical and subclinical optic neuritis. Optical coherence tomography (OCT) measures were unrelated to disability and demographic features predicting a worse prognosis in multiple sclerosis. OCT may provide complementary information to VEP in select cases, and remains a valuable research tool for studying optic nerve disease in populations.

Figure 1 Box plot of retinal nerve fiber layer thickness categorized by visual acuity outcome Optical coherence tomography (OCT) is able to distinguish unaffected from normal and normal from mild, but not mild from moderate, severe, or profound. Note that the median value is approximately 50 μm, starting from the mild category through the profound.

Figure 2 Box plot of retinal nerve fiber layer thickness categorized by contrast sensitivity outcome Optical coherence tomography (OCT) is able to distinguish unaffected from normal and normal from mild, but not mild from moderate or severe. LogMAR = logarithm of the minimum angle of resolution.

Figure 3 Box plot of retinal nerve fiber layer changes with repeated episodes of optic neuritis Discrete recurrence of optic nerve inflammation was associated with a decremental decline in the retinal nerve fiber layer. OCT = optical coherence tomography.

Figure 4 Box plot comparing retinal nerve fiber layer thickness categorized by use of IV glucocorticoids The nadir acuity during the acute episode was stratified to prevent a bias toward a preferential use of IV steroids for those with severe clinical disease. Only first episodes of optic neuritis were analyzed. There was no difference in retinal nerve fiber layer thickness with glucocorticoids for the mild/moderate or severe groups. OCT = optical coherence tomography.