TED: Strabismus - When and How to Operate

Restrictive strabismus with diplopia occurs in 30-50% of patients in thyroid eye disease (TED) due to a decrease in muscle fiber elasticity caused by the direct infiltration of inflammatory cells, related to cytokines and eventually fibrosis of the extra ocular muscle1. Impairment of motility occurs significantly more often in smokers and older patients2. Several extraocular muscles may be affected although single unilateral muscle involvement can also occur. Hypertropia with restricted elevation due to inferior rectus involvement and esotropia with restricted abduction from medial rectus involvement are the most common types of restrictive strabismus in TED3. The lateral rectus and the oblique muscles are the least affected. Early in the process most patients typically adopt a chin-up posture due to a tight inferior rectus muscle. New onset diplopia can also occur after orbital decompression because of changes in muscle pads and orbital anatomy. Esotropia is most common after medial orbital wall decompression due to displacement of the medial recti muscles in the ethmoid sinus.