Combined use of orbital soft tissue volume and retinal microvessel density for diagnosing dysthyroid optic neuropathy

To (i) detect changes in orbital soft tissue and retinal microstructure occurring in thyroid-associated ophthalmopathy (TAO), (ii) investigate the relationship between these variables and their bearing on visual impairment, and (iii) determine their combined diagnostic utility for dysthyroid optic neuropathy (DON).

Enrolled in this retrospective study were patients with TAO eyes, which included the DON group, equivocal DON (eDON) and non-DON (nDON). Patients were divided into three experimental groups: DON (n = 18 eyes), eDON (n = 24 eyes), and nDON (n = 20 eyes). At the same time, a healthy control (C) group was included (n = 30 eyes). A three-dimensional (3D) volume index, obtained by reconstructing orbital soft tissue via computed tomography (CT) and Mimics software, was used. Optical coherence tomography angiography (OCT-A) was used to monitor and record retinal microstructural properties, i.e., microvessel density and thickness.

The DON group had significantly lower density and thickness of the retinal vasculature compared to the other groups (p < 0.05), with the exception of deep macular capillary density (MDRCP-VD), which was not statistically significant. In terms of soft-tissue volumes, the DON group had considerably higher orbital fat (OFV/BOV) and extraocular muscle indices (EOMV/BOV) than did the other groups; in contrast, the muscle cone inner volume index (MCIV/BOV) was lower (p < 0.05). A combination of the macular superficial retinal capillary plexuses (MSCRP-VD), optic nerve head vessel density-whole images (ONH-wiVD), MCIV/BOV, and EOMV/BOV yielded the highest values (AUC: 0.954, sensitivity: 95%, specificity: 88.1%) for the diagnosis of DON compared to the other groups.

EOMV/BOV plus MCIV/BOV, combined with MSRPC-VD plus ONH-wiVD, appears to provide the most accurate diagnostic guideline for DON. Further, 3D reconstructions of orbital soft tissue, in conjunction with OCT-A images, offer an innovative approach not only for preventing permanent loss of vision but also for enhancing the accuracy of diagnosing DON and its early stages.