Correlation of the Electrophysiological and Optical Coherence Tomography Changes in patients with Thyroid-Associated Ophthalmopathy

Abstract

Purpose: to study the structural and functional changes of the optic nerve & macula in patients with thyroid-associated ophthalmopathy (TAO) patients. Methods: Cross-sectional clinical study including 40 cases with TAO and 40 age and sex-matched healthy participants as a control. Complete ophthalmological assessment, evaluation of the proptosis, spectral domain OCT, and electrophysiological investigations (pattern electroretinogram [PERG], multifocal ERG (mfERG) & visual evoked potentials (PVEP) were performed to all participants. Results: Retinal nerve fibre (RNFL), central foveal (CFT) thickness and mean inner macular ring thickness are thinner in cases with proptosis. MfERG showed lower Retinal Response Density1 (RRD1), Ring 1 P1 amplitude and lower five-rings N1 amplitude. Central foveal thickness showed significant positive correlation with VA, BCVA, P50 amplitude and R1 N1 amplitude (r = 0.64, 0.65, 0.40 and 0.51 with p < 0 .001, < 0 .001, < 0 .001 and < 0 .001 respectively), and negative correlation with duration of the disease, degree of proptosis, clinical activity score and R1 N1 latency (r = -0.59, -0.78, -0.41 & -0.90 with p <0.001, <0.001, <0.001 & <0.001 respectively). RNFL thickness showed negative correlation with duration of the disease, degree of proptosis and clinical activity score (-0.77, -0.71 & -0.85 with p < 0 .001, < 0 .001 & < 0 .001 respectively). Multiple regression analyses showed that the degree of proptosis and P50 amplitude were the most important determinants for CFT (p = 0.03 & 0.02); whereas the duration of the disease, and activity score were the most important determinants for average RNFL thickness (p =‎ 0.004, and < 0.001‎ respectively). Conclusion: In the absence of fundus changes, macular thinning together with functional changes detected by PERG and mfERG could be used as good predictors of subclinical retinopathy in the cases of TAO.