Reduced macular inner retinal thickness and microvascular density in the early stage of patients with dysthyroid optic neuropathy

Background The goal was to investigate changes of the inner intra-retinal layer thicknesses and retinal capillary density (RCD) around the macula in thyroid-associated ophthalmopathy (TAO) patients with or without dysthyroid optic neuropathy (DON). Methods Forty-four TAO patients including 23 non-DON and 21 DON patients, and 38 healthy participants were enrolled. Spectral domain optical coherence tomography equipped with Angiovue was used to obtain three-dimensional retinal thickness maps and microvascular images of the superficial and deep retinal capillary layers (SRCL and DRCL, respectively) around the macula. Quantitative analyses were performed using a custom automated algorithm. Results The thicknesses of the nerve fiber layer, ganglion cell layer + inner plexiform layer, and ganglion cell complex (GCC) as well as the RCDs in the SRCL and DRCL in both TAO groups were significantly decreased compared to the controls. In addition, the RCDs in DRCL of the DON group were further decreased compared to the non-DON group. GCC thickness in both TAO groups was positively correlated with the RCDs of the SRCL in the total annular zone and in the temporal, inferior, and nasal sectors. The areas under the receiver operating characteristic curves for the GCC thickness combined with the RCD were generally larger than those of each single indicator. Conclusions Thinned inner intra-retinal layers and decreased RCDs in the TAO patients without DON revealed that morphological changes might precede visual dysfunction. The composite index of the retinal structure and the microvascular density might be valuable in the diagnosing, monitoring, and intervention for early DON.