Multifocal visual evoked potential in thyroid associated ophthalmopathy

PURPOSE: To assess the visual function in patients with thyroid associated ophthalmopathy (TAO) without clinical optic neuropathy by multifocal visual evoked potential (mfVEP) and to correlate the findings with Humphrey visual field (HVF) and optical coherence tomography (OCT). METHODS: This observational case-control study recruited a consecutive group of euthyroid TAO patients (excluding those with optic neuropathy) and a healthy matched control group. Ophthalmological assessment was done followed by HVF test, OCT retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC), and mfVEP. For mfVEP, results were reported as mean signal-to-noise ratio (SNR) of upper and lower sectors of rings 5-6 (9.9°-22°). RESULTS: Thirty patients were included in each group (TAO patients and controls). No significant differences were observed between the groups in RNFL thickness, GCC thickness, or upper/lower hemifield VF parameters. Analysis of the mfVEP revealed that, before multiple comparisons correction, SNR was lower in TAO patients. A repeated measures analysis of variance confirmed significant main effects for both patient group (p = 0.004), and test location (comparing SNR in the upper vs. lower sectors of rings 5-6) (p < 0.001), but no significant interaction. CONCLUSION: In this limited cohort, initial analysis of mfVEP results suggested reduction of the SNR in TAO patients without clinical optic neuropathy, but these findings did not remain statistically robust after adjustment for multiple comparisons. mfVEP alterations occurred despite normal OCT and visual field findings and warrant further evaluation in larger, longitudinal studies.