Investigation of corneal structural changes by in vivo confocal microscopy in thyroid-associated ophthalmopathy patients

Purpose To investigate the corneal subbasal nerve plexus (SBP) and dendritic cell (DC) density changes in patients with thyroid-related ophthalmopathy (TAO) using in vivo confocal microscopy (IVCM). Methods Thirty-three patients with inactive TAO and 36 healthy controls were included. All participants underwent comprehensive ophthalmologic examinations and IVCM. Corneal nerve fiber length (CNFL), density (CNFD), branch density (CNBD), total branch density (CTBD), fiber area (CNFA), fiber width (CNFW), fractal dimension (CNFrD) and DC density were analyzed using semi-automated and automated methods. Clinical features, ocular surface parameters, and correlations with IVCM findings were assessed. Results TAO patients exhibited significant reductions in CNFL, CNFD, CNBD, CTBD, CNFA, CNFrD and increased DC density compared to controls ( p < 0.05). CNBD and CNFrD demonstrated the highest diagnostic sensitivity and specificity. Corneal nerve damage and increased DC density correlated with worsened ocular surface parameters, including reduced non-invasive average tear break-up time, The Schirmer test values and increased ocular surface disease index score. No significant association was found between IVCM parameters and systemic markers such as Clinical Activity Score, thyroid-stimulating hormone (TSH) and disease duration. Conclusion TAO patients show corneal nerve degeneration and inflammation detectable by IVCM. These findings highlight immune-mediated mechanisms underlying corneal SBP damage and their association with ocular surface dysfunction, underscoring the potential of IVCM in clinical assessments and targeted therapeutic strategies.