1. 4-3
Lid Lag

2. Lid Lag
Von Graefe Sign
Persistent elevation of the upper lid on downgaze

3. Classical Signs: TAO A prominent stare. Retraction of all four eyelids
Bilateral exophthalmos
Hertel exophthalmometer 25 OD, 28 OS, base 108.
Tight orbits/reduced orbital resilience
Prominent congested scleral blood vessels
A visible rim of sclera on gentle eye closure

4. 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

5. Limited Upgaze
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.

6. Limited Upgaze Duction Test
1. Anesthetize the eye with topical anesthesia
2. Push on the globe with a cotton tip
3. Pull with blunt tweezers to try to move eye up.
Mechanical restriction - a positive forced duction test.

7. Compressive Optic Neuropathy
Most serious complication
Crowding of the orbital apex by enlarged ocular muscles
Present in 50% severe cases TAO
May require urgent orbital decompression

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

9. 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.