Sectoral and Layer-Specific Corneal Thinning in Thyroid Eye Disease: A Cross-Sectional Study

Corneal thickness in patients with thyroid eye disease (TED) and the layer or specific region of the cornea primarily affected by corneal thickness changes remain unclear. This study aimed to examine and compare the differences in corneal thickness across various layers in patients with TED and a control group, focusing on identifying the specific corneal region where these changes are most pronounced.

This cross-sectional retrospective study included 57 eyes from 29 patients with TED and 18 eyes from 9 control participants. Basic eye examinations and corneal topography measurements were performed using a Galilei dual Scheimpflug camera and RTVue. Total corneal thickness, corneal epithelial thickness, and corneal stromal thickness (CST) were evaluated.

Screening indices related to corneal irregularity, such as keratoconus prediction index and opposite sector index, were numerically higher in the TED group but remained within normal limits. In all corneal sectors, the mean total corneal thickness and CST were significantly lower in the TED group (e.g., central CST, 480.33 ± 28.79 µm in TED vs. 498.94 ± 16.04 µm in controls; P = 0.049). Notably, no significant differences in corneal epithelial thickness were observed between the two groups across all evaluated sectors.

Patients with TED demonstrated diffuse stromal thinning that preserved the normal sectoral distribution pattern, without focal ectatic changes or topographic abnormalities. These findings highlight the need for layer-specific corneal assessment in patients with TED, particularly when evaluating corneal health and planning anterior segment procedures.

These findings indicate that TED is linked to structural changes in the cornea, especially within the stromal layer, which may have important clinical implications for managing TED-related ocular complications.