A patient presents with tachycardia. You notice the eyes seem wide. Is this the lid lag of hyperthryoidism?
The terminology of the opthalmologic signs of hyperthyroidism is sometimes excessively parsed. It is lagophthalmos when the eye does not close, von Grafe’s sign when the act of looking down causes a temporary lid retraction, and lid lag when the lid appears persistently retracted while looking down.(Harvey Opthalm Surg 1981)
It is probably sufficient to use the term lid lag for any of these conditions. The pathophysiology is the opposite of the ptosis of Horner’s syndrome. The sympathetically-innervated Mueller’s muscle has an increase rather than a decrease in the tone. As for its sensitivity and specificity, most studies neglect to record this sign.
We are not discussing here the other opthalmologic findings specific to Grave’s disease, which result from myxedema/swelling.
Take Home Points:
Hyperthyroidism causes increased tone in Mueller’s muscle, which causes lid lag