Peripapillary structural and microvascular alterations in early dysthyroid optic neuropathy

Background To explore the changes in blood supply and structure around the optic nerve head (ONH) in thyroid-associated ophthalmopathy (TAO) patients with suspected dysthyroid optic neuropathy (DON). Methods TAO patients [19 with DON; 24 non-DON (NDON); 20 with equivocal DON (EDON)], and 34 control subjects were examined. Optical coherence tomography angiography (OCTA) was used to obtain peripapillary retinal nerve fiber layer (p-RNFL) and vessel density parameters, including the ONH whole image vessel density (ONH-wiVD) and the radial peripapillary capillary vessel density (RPC-VD) in early DON. Results Although there were no differences in p-RNFL thickness among the groups, there were differences in the ONH-wiVD of each grid section and the RPC-VD in all areas (P < 0.01). Compared with healthy controls, the EDON eyes had significantly lower RPC-VDs in all aeras (P < 0.05).The peripapillary region was further divided into eight sectors, and the RPC-VD in the temporal upper, superior temporal, and temporal lower sectors in the EDON group were significantly lower than in the controls. The visual impairment was closely related to the loss of peripapillary capillary vessel density. Univariate correlation analysis showed that the ONH-wiVD and RPC-VD of the TAO groups were negatively correlated with the intraocular pressure (r = - 0.296, P = 0.006; r = - 0.258, P = 0.016 respectively). Conclusions EDON patients had significantly lower ONH-wiVD and RPC-VD than control subjects, and the temporal and upper VDs were more likely to be affected in the early stage of TAO. The combined use of spectral domain optical coherence tomography and OCTA technologies offer a new method for early diagnosis of suspected DON patients.