How to Test for Lid Lag
Lid lag is tested by having the patient look downward from primary gaze while you observe whether the upper eyelid maintains an abnormally high position relative to the globe during the downward eye movement. 1
Testing Technique
To properly assess for lid lag:
- Position the patient in primary gaze (looking straight ahead)
- Instruct the patient to look downward slowly and smoothly
- Observe the upper eyelid position as the eye moves from primary position to downgaze
- Measure or note if the eyelid remains higher than expected relative to the globe in the downward position
The key finding is a static elevation of the eyelid margin in downgaze - the lid sits higher than normal when the eye is looking down 1. Normal lower eyelid excursion during downgaze is 3-4 mm 2.
Important Distinctions
Do not confuse lid lag with von Graefe's sign, though they are often incorrectly used interchangeably 3, 1:
- Lid lag = static finding where the eyelid is positioned higher than normal with the globe in downgaze
- Von Graefe's sign = dynamic finding describing retarded/delayed descent of the eyelid during the actual movement from primary position to downgaze 1
- Lagophthalmos = inability to completely close the eyes (a separate finding) 1
Clinical Context
Lid lag is particularly relevant when evaluating for:
- Thyroid eye disease (Graves' ophthalmopathy) - though interestingly, true lid lag occurs in only 8% of Graves' patients, while von Graefe's sign occurs in 36% 3
- Eyelid retraction - which occurs in 38% of Graves' patients 3
Levator excursion measurement may actually be more clinically useful than lid lag grading in thyroid eye disease, as decreased levator function correlates with both increased lid lag and lagophthalmos 4.
Examination Sequence
Test for lid lag as part of the external examination during ocular motility assessment 5, specifically:
- Before instilling any drops
- During evaluation of ductions and versions
- When assessing eyelid position and character