Lower lid retraction in thyroid orbitopathy: lamellar shortening or proptosis?

To investigate any correlation between lower lid retraction and proptosis and also between lower lid retraction and lamellar length, as measured by fornix depth, in patients with thyroid eye disease (TED). One hundred and sixty-six eyes of 83 patients with TED were enrolled. The inferior fornix depth, Hertel exophthalmometry measurement, clinical activity score, and lower lid position were the main outcome variables. The correlation between lower lid position measurement and Hertel measurements and also between the lower lid position measurement and inferior fornix depth were evaluated using ANOVA and Pearson's tests. The mean age of subjects in patients with and without lid retraction was 42.8 ± 1.5 and 47.7 ± 1.6 years, respectively (P = 0.4). The inferior fornix depth in patients with and without lower lid retraction was 11.8 ± 1.5 and 11.8 ± 1.3 mm, respectively (P = 0.960). Pearson's analysis showed a significant correlation between the degree of proptosis and lower lid retraction in TED patients (P = 0.01). However, no significant correlation was found between the level of lower lid retraction and the fornix depth (P = 0.87). The main cause of lower lid retraction in TED is proptosis. The beneficial effect of orbital decompression on improvement of lower lid retraction must be considered during a stepwise surgical approach in TED patients.