Detection of Dysthyroid Optic Neuropathy by Optical Coherence Tomography

Abstract Objectives: This study aimed to compare the measurements of the peripapillary nerve fiber layer (RNFL) thickness obtained by OCT in patients with TAO and healthy controls and to correlate these parameters with the severity of the orbital disease.Methods: The cross-sectional single-center study consisted of 74 patients (45 with TAO and 29 healthy controls). Patients with TAO underwent a complete ophthalmological examination and were divided according to the clinical activity score (CAS) and European Group Graves' Orbitopathy severity (EUGOGO) classification. Spectral-domain OCT assessed the measurements of the peripapillary RNFL. Results: There was no statistical difference between the groups regarding demographic characteristics and comorbidities (p>0.05%). According to CAS, 93.3% of patients with TAO were in the inactive phase. By the EUGOGO, 27% had mild TAO, 66% had moderate-to-severe, and 7% had very severe disease. The mean peripapillary RNFL thickness was thinnest in the temporal quadrant in the TAO group (p<0.05). There was a strong association between the severity of TAO and the reduction in peripapillary RNFL thickness (p<0.001), except in the nasal quadrant. Conclusion: These results suggest that OCT can be a valuable tool in detecting early changes in peripapillary RNFL in patients with TAO, even in the inactive phase when neuropathy is not yet clinically detectable. These parameters appear to be potential adjuncts in the follow-up of patients, especially when there is a risk of visual loss.