How is brow ptosis measured and diagnosed?

How to Measure and Diagnose Brow Ptosis

Brow ptosis is diagnosed through clinical examination by measuring brow height relative to the supraorbital rim and assessing for associated functional deficits, particularly visual field obstruction from excess soft tissue pushing downward on the eyelid. 1

Clinical Measurement Techniques

Brow Position Assessment

• Measure brow height from the supraorbital rim using standardized photography or direct clinical measurement 2
• Normal brow position: In women, the brow should be above the supraorbital rim; in men, it should be at or slightly above the supraorbital rim 2
• Document both medial and lateral brow positions separately, as lateral brow ptosis typically occurs earlier and more severely than medial ptosis 3
• Average lateral brow elevation of 2.54 mm from baseline can be used as a reference point for assessing severity 2

Key Examination Components During External Assessment

• Evaluate eyelid position and levator function as part of the external examination, noting the presence of ptosis and relative globe position 4
• Assess for compensatory brow elevation (fixation duress) by observing brow position during attempted ocular elevation, which may indicate restrictive strabismus but also reveals involuntary brow compensation 4
• Measure marginal reflex distance (MRD1) to differentiate between true eyelid ptosis and pseudoptosis from brow descent 5

Functional Assessment

Visual Field Impact

• Perform visual field testing to document superior field defects caused by excess soft tissue from brow ptosis 1
• Functional brow surgery is indicated when severe brow asymmetry or visual field deficit results from excess soft tissue pushing downward on the eyelid 1

Mechanical vs. Compensatory Brow Elevation

• Test mechanical brow elevation by manually lifting the brow to assess whether eyelid position changes—in true eyelid ptosis, mechanical brow elevation does not significantly change eyelid position 5
• Observe voluntary brow elevation patterns, as patients with ptosis show greater coupling between brow and eyelid margin during maximal eyelid opening compared to controls 5

Anatomical Considerations for Diagnosis

Pattern Recognition

• Lateral brow ptosis develops earlier than medial ptosis due to less structural support lateral to the temporal fusion line of the skull 3
• The temporal fusion line serves as the axis point where forces acting on the brow converge, making lateral descent more pronounced 3

Associated Conditions to Evaluate

• Assess for floppy eyelid syndrome, which presents with upper eyelid edema, easily everted upper eyelid, and may be associated with ptosis 4, 6
• Evaluate for giant papillary conjunctivitis or giant fornix syndrome, both of which can present with ptosis as a clinical sign 4
• Rule out thyroid eye disease when brow elevation with eyelid retraction is noted on attempted ocular elevation (fixation duress), as this indicates restrictive strabismus rather than primary brow ptosis 4

Common Pitfalls to Avoid

• Do not confuse compensatory brow elevation in eyelid ptosis with primary brow ptosis—the brow elevation in eyelid ptosis is driven by efforts to raise the eyelid via co-innervation, not mechanical compensation 5
• Avoid assuming uniform brow descent—always measure medial and lateral segments separately, as asymmetric patterns are common and clinically significant 2, 3
• Do not overlook functional deficits—even mild-appearing brow ptosis can cause significant visual field restriction requiring documentation 1