Thyroid Associated Orbitopathy (TAO)

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Classical Signs : TAO

A prominent stare. Retraction of all four eyelidsBilateral exophthalmos Hertel exophthalmometer 25 OD, 28 OS, base 108.Tight orbits/reduced orbital resilienceProminent congested scleral blood vesselsA visible rim of sclera on gentle eye closure

Eye movements

Lid lag (persistent elevation of the upper eyelid in downgaze) – von Graefe sign

Marked limitation of upward gaze

Mild limitation of downgaze

Restricted horizontal eye movements

Positive forced duction test

Limitation of upgaze is due to tethering of the eyeball in the floor of the orbit by soft tissue changes.

Tethering of the eyeball inferiorly can be confirmed by a forced duction test.

TAO – Limited Upgaze

TAO

Anesthetize the eye with topical anesthesia

Push on the globe with a cotton tip swab or

Pull with blunt tweezers to try to move eye up.

Mechanical restriction - a positive forced duction test.

Duction Test:

Most serious complication

Crowding of the orbital apex by enlarged ocular muscles

Present in 50% severe cases TAO

May require urgent orbital decompression

Compressive Optic Neuropathy

Figure 1 Axial CT through the orbit without contrast shows enlargement of the medial rectus muscle bilaterally. Note that the tendinous insertion is spared.

Figure 2 The coronal CT (reformatted from axial data set) without contrast shows enlargement of the medial rectus muscle, inferior rectus muscle and upper muscle complex on both sides. Courtesy of Hugh Curtin, M.D.

http://www.lib.med.utah.edu/NOVEL