This is a cross-sectional study, with the convenience sampling method, and we aim to evaluate macular microcirculation in patients with TAO compared to healthy individuals. TAO was defined in the presence of at least two of the following: concurrent or recently treated immune-related thyroid dysfunction, typical ocular signs, and radiographic evidence of thyroid eye disease. We divided all participants into patients and control groups. The participants of the control group were called from the hospital staff who volunteered to participate in the study. All groups were matched for age and gender. Subjects with the following conditions were excluded from the study: previous ocular surgeries in the past 6 months, intraocular pressure > 20 mmHg, any history of glaucoma, age < 18 years old, refractive error more than 3 diopters of spherical equivalent, any diseases that can affect the neurovasculature of the retina such as uveitis or diabetes mellitus, pregnancy or breastfeeding, and consumption of oral contraceptive pills.

This study was carried out according to the Declaration of Helsinki, and the Mashhad University of Medical Sciences ethical committee approved this study (approval number: IRMUMSMEDICALREC.1399.260). We obtained informed consent from the participants.

All participants underwent best-corrected distance visual acuity (BCVA) measurement with thumbing E chart, slit-lamp biomicroscopy, Goldmann applanation tonometry, and complete dilated fundus examination (using a + 90D condensing lens). To determine the activity of TAO, we used the Clinical Activity Score (CAS) system [7], which includes the evaluation of 7 items as follows: spontaneous orbital pain, gaze-evoked orbital pain, eyelid swelling, eyelid erythema, conjunctival redness, chemosis, and inflammation of the caruncle or plica. Each item is rated one (if that item is positive) or zero. A total score of three or more is considered an active disease. According to this scoring system, we subdivided the patient group into two subgroups: the patients with CAS < 3 and the patients with CAS ≥ 3. All patients were biochemically euthyroid at the time of examinations.

All participants underwent macular optical coherence tomography angiography (AngioVue RTVue XR Avanti, Optovue, Fremont, CA, USA, software version: 2018,0,0,18) with 6 * 6 mm scan size. Superficial and deep capillary plexus were analyzed. Foveal vessel density (VD) was defined as the density of the superficial capillary plexus (internal limiting membrane to inner plexiform layer) in a 1 mm diameter circle centered on the center of the fovea. Parafoveal VD was defined as the ring occupying the area between the foveal area and the 2.5 × 2.5 mm area centered on the foveal center. Vessel densities were calculated automatically. Furthermore, the neuro-vasculature of the ONH was evaluated with OCTA imaging (AngioVue RTVue XR Avanti, Optovue, Fremont, CA, USA) of the disc. To detect the ONH vasculature an area of 4.5 × 4.5 mm centered on the (ONH) which included the papillary and peripapillary regions. To obtain the vascular density (VD) of the papillary area, the VD image was merged with the en-face OCT image of the ONH region with the built-in software of the device, and the papillary VD was calculated automatically. For the peripapillary area VD measurement, two circles were centered on the center of the ONH on the en face OCT image by a trained operator, one at the margin of the disc and the other at a radius of 2.25 mm from the center of the disc (4.5 mm diameter). The doughnut-shaped area made between them was defined as the peripapillary area. Radial peripapillary capillary (RPC) plexus density was measured both as a whole image (360 degrees around the ONH) and superior/inferior semicircles. Any images with a quality index below 6/10 were discarded, and the imaging was repeated (Figs. 1 and 2). Images were taken without any pharmacologic mydriasis and after 3–5 min of rest. All measurements were taken at 8–12 a.m. Any images with a quality index below 6/10 were discarded, and the imaging was repeated. The macular and peripapillary vascular profile includes foveal superficial and deep vessel density, parafoveal superficial and deep vessel density, foveal avascular zone (FAZ) area, radial peripapillary capillary (RPC) plexus density, and peripapillary retinal nerve fiber layer thickness (PRNFL) were analyzed and compared between the groups.

We used Statistical Package for Social Sciences (SPSS) software version 22 (IBM SPSS Statistics, IBM Corporation, Chicago, IL) for statistical analysis. We used the Shapiro-Wilk test to analyze the distribution of data. The characteristics of the subjects are described by descriptive statistical methods including central indices and indices of dispersion. We used the chi-square test to investigate the relationship between the qualitative variables and the independent samples t-test or its non-parametric equivalent to compare the quantitative variables between the groups. In all calculations, p < 0.05 was considered a significant level.

Representative image of the macular OCTA.

Representative image of optic nerve head OCTA.