To evaluate the clinical features of dry eye in thyroid-associated ophthalmopathy (TAO) according to disease activity and analyze the related factors.

This study included 157 patients diagnosed with TAO and dry eye between March 2009 and March 2015. According to the clinical activity score (CAS), TAO patients were divided into inactive (CAS < 3) and active (CAS ≥ 3) groups. Clinical features included age, sex, visual acuity, proptosis, palpebral fissure width, orbital computed tomography (CT) findings, thyroid hormones, and ocular surface parameters including tear film break-up time (TFBUT), Schirmer tests, keratoepitheliopathy scores, and ocular surface disease index (OSDI) were obtained and compared between the groups. In addition, correlations between clinical features and ocular surface parameters were analyzed in both groups.

In the inactive and active TAO groups, CAS was 1.24 ± 0.69 and 4.23 ± 1.13, respectively ( p = 0.001). Thyrotropin-binding inhibitory immunoglobulin was significantly higher in the active TAO group than in the inactive TAO group ( p = 0.048). On orbital CT, extraocular muscle hypertrophy was more common in the active TAO group than the inactive TAO group ( p = 0.020). No significant difference was found in age, sex, visual acuity, free T4, and thyroid-stimulating hormone between the two groups. During analysis of the tear film and ocular surface parameters, TFBUT ( p = 0.006) was shorter and OSDI score ( p = 0.028) was higher in the active TAO group than the inactive TAO group. TFBUT was negatively correlated with proptosis (r = -0.432, p = 0.001; r = -0.308, p = 0.032) and palpebral fissure width (r = -0.367 p = 0.012; r = -0.312, p = 0.031) in both groups. OSDI was positively correlated with proptosis in the active TAO group (r = 0.301, p = 0.033).

TFBUT was shorter and OSDI score higher in dry eye patients with active TAO than in patients with inactive TAO. The TFBUT was negatively correlated with proptosis and palpebral fissure width in both groups.