Volumetric Analysis of Orbital Soft Tissues in Thyroid Eye Disease: Correlations With Clinical Characteristics

Abstract

Purpose : Using a novel atlas-based segmentation method, we aimed to identify whether specific orbital soft tissue volumes in patients with thyroid eye disease (TED) correlated with patient and clinical characteristics.

Methods : A retrospective chart review was performed to identify patients with a diagnosis of TED who had been evaluated clinically by an oculoplastic surgeon and had a CT scan of the orbits. Patient characteristics included age, sex, race, smoking status, and body mass index (BMI). Clinical characteristics including Clinical Activity Score (CAS) and strabismus were evaluated with respect to soft tissue volume measurements for each extraocular muscle (EOM) and orbital fat. Statistical analyses were performed using R software (version 4.0.3). Multiple regression analysis and Pearson’s correlation were used to evaluate data. Significance was defined as p<0.05.

Results : 37 patients were evaluated (22 female, 15 male). CAS ranged from 0-5, and 7 patients had documented strabismus. There was no statistically significant correlation between orbital EOM volumes and age (p=0.382), sex (p=0.808), race (p=0.623), smoking status (p=0.684), or BMI (p=0.744). Furthermore, there was no statistically significant correlation between orbital fat volume and age (p=0.520), sex (p=0.934), race (p=0.640), smoking status (p=0.695), or BMI (p=0.700). Overall, EOM and orbital fat volumes showed high correlation with each other (Table 1). However, there was no statistically significant correlation between EOM volumes and CAS (p=0.483) or strabismus (p=0.174); there was also no statistically significant correlation between fat volume and CAS (p=0.514) or strabismus (p=0.163).

Conclusions : There is no significant correlation between orbital soft tissue volumes and patient characteristics (age, sex, race, BMI), and surprisingly no correlation with smoking status (a known risk factor for TED) among patients in our TED cohort. While orbital soft tissue volumes show high correlation with each other, they collectively do not correlate significantly with clinical characteristics such as CAS and strabismus. For CAS, this finding is not entirely unexpected as CAS is a measure of activity rather than severity; for strabismus, this implies there may be qualities other than orbital soft tissue volume which are important in determining strabismus.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Table 1. Pearson's correlation for orbital fat and EOM tissue volumes