Cross-sectional areas of the five EOMs bilaterally (excluding IO) were obtained from the coronal T1w images by outlining regions of interest (ROI) around the outer border of each muscle, one slice behind the posterior border of the globe, using the FSLView software (FMRIB, Oxford, UK), and the cross-sectional area of each was recorded. All measurements were performed by a single observer (R.D.S.P) and reviewed by a second observer (I.D.) for quality control purposes.