Evaluation of clinical features and prognostic factors in patients with thyroid ophthalmopathy

Purpose: To evaluate the clinical features, ocular parameters and prognostic factors of thyroid ophthalmopathy patients according to their clinical activity scores and compare them with healthy controls. Material and Methods: This cross-sectional study included 77 eyes of 40 patients with thyroid orbitopathy and 80 eyes of 40 healthy controls who applied to the Ophthalmology Department of Çukurova University Faculty of Medicine between 2021-2024. Patients were evaluated according to the clinical activity score (CAS) and categorized into two groups as CAS 0-2 and CAS ≥3. Age, gender, duration of Graves' disease and applied treatment (antithyroid drug), systemic disease history, smoking history and duration, and presence of diplopia were recorded. Best corrected visual acuity (BCVA), intraocular pressure (IOP) measurement in primary and upward gaze positions, biomicroscopic anterior segment and fundus examinations, thyroid function tests, magnetic resonance imaging (MRI) findings, and proptosis degrees with Hertel Exophthalmometer were examined. The hemodynamics of the vascular structures in the orbit, optic disc, retinal and choroidal microvascular changes, corneal morphology and biomechanics of all thyroid orbitopathy patients were evaluated and compared with healthy controls. Results: In our study, the BCVA of both patient groups were found to be lower in comparison with controls, and higher in age, duration of smoking, primary and upward gaze IOP and Hertel Exophthalmometer values (p<0.05 for all). In thyroid function tests, free t3 value and diplopia were observed to be higher in CAS≥3 compared to CAS 0-2 (p=0.01, p<0.001). In CAS≥3 patients, intraorbital fat tissue thickness, exophthalmus degree, superior, inferior, medial rectus and inferior oblique muscles, lacrimal gland lengths were observed to increase compared to CAS 0-2 patients (p<0.05 for all). In both patient groups, significant differences were observed in the peak systolic velocity of the ophthalmic artery, the resistance index of the central retinal artery, the peak systolic velocity and resistance index of the posterior ciliary artery compared to the control group (p<0.05 for all). İn macular Optic coherence tomography angiography (OCTA) evaluations, both patient groups compared to controls showed significant differences in foveal avascular zone (FAZ), superficial capillary plexus (SCP) [whole image, all quadrants of foveal, parafoveal and perifoveal regions (p<0.05 for all)] and deep capillary plexus (DCP)[whole image, foveal, parafoveal (superior and nasal), perifoveal (temporal, superior and inferior) (p<0.05 for all)]. İn OCTA disc evaluations, inside-disc and radial peripapillary capillary plexus in both patient groups compared to controls, differed only in the temporal inferior quadrant. Whereas, retinal nerve fiber layer (RNFL) differed in the peripapillary region and inferior nasal quadrant (p<0.05 for all). In Optic coherence tomography (OCT) findings, significant differences were observed in the two patient groups compared to controls in choroidal thickness and nasal inferior part of RNFL (p=0.001, p=0.01, respectively). In both patient groups, significant differences were observed in the anterior, posterior elevation, Db in corneal topography, and in the corneal biomechanical evaluation, significant differences were observed in the first applanation velocity(A1V), peak distance (PD), deformation amplitude(DA), highest concavity radius, biomechanically corrected IOP (bIOP), tomographic biomechanical index (TBI) and in whole eye movement(WEM) (p<0.05 for all). Conclusion: With the increase in clinical activity score, in the MRI findings exophthalmus, intraorbital fat tissue thickness, lacrimal gland and extraocular muscles lengths' were observed to increase in the CAS≥3 patient group compared to CAS 0-2.With the increase in clinical activity score of thyroid ophthalmopathy patients, microvascular and structural changes occurred in the macula, optic disc and choroid. The blood flow increased in orbital vascular structures, and changes were also detected in corneal morphology and biomechanics compared with healthy controls. However, our results need to be supported by larger, more comprehensive and prospective studies. Keywords: Thyroid ophthalmopathy, magnetic resonance imaging, vessel density, ocular blood flow, corneal dynamic scheimpflug analyser