Classification of Eyelid Ptosis on Clinical Examination
The degree of eyelid ptosis is clinically classified as mild (1-2 mm), moderate (3-4 mm), or severe (>4 mm) based on the measurement of upper eyelid drooping relative to normal position.
Measurement Technique
- Ptosis is present when the upper eyelid margin is less than 2 mm from the midpupil 1
- Measurements should be taken with the patient in primary gaze position, recording the distance from the upper eyelid margin to the center of the pupil 2
- Asymmetric ptosis is diagnosed when there is 2 mm or more difference between the heights of the two upper eyelids, even if both eyelids are 2 mm or more from midpupil 1
- Clinical measurements should be compared with photographic documentation when possible for accuracy 1
Classification by Severity
- Mild ptosis: Upper eyelid droops 1-2 mm below normal position 2
- Moderate ptosis: Upper eyelid droops 3-4 mm below normal position 2
- Severe ptosis: Upper eyelid droops more than 4 mm below normal position, potentially covering the pupil entirely 2
Additional Assessment Parameters
- Levator function should be measured as part of the ptosis evaluation and classified as 3:
- Good: >10 mm of excursion
- Fair: 5-10 mm of excursion
- Poor: <5 mm of excursion
- Document presence of compensatory mechanisms such as frontalis muscle activation, chin-up head position, or manual lifting of the eyelid 2
- Note whether ptosis is unilateral or bilateral 2, 3
- Evaluate for associated findings such as anisocoria, pupillary abnormalities, or other neurological deficits 4
Clinical Examination Elements
- Complete sensorimotor examination to detect any associated strabismus 4
- Slit-lamp examination for mechanical causes of ptosis 4
- Assessment for floppy eyelid syndrome, which presents with upper eyelid edema and an easily everted upper eyelid 4
- Evaluation for papillary conjunctivitis, which may be associated with ptosis in conditions like giant papillary conjunctivitis 5
- Check for horizontal lid laxity, which may be present in conditions like floppy eyelid syndrome 5
Common Pitfalls to Avoid
- Failing to distinguish true ptosis from pseudoptosis (apparent drooping due to dermatochalasis, brow ptosis, or contralateral lid retraction) 3
- Missing pupil-involving third nerve palsy, which can represent a neurosurgical emergency 4
- Overlooking variable ptosis that worsens with fatigue, which may indicate myasthenia gravis 4
- Not considering the functional impact on vision, as ptosis can reduce the upper visual field to 30 degrees or less in 97% of affected eyes 1
By systematically evaluating and documenting these parameters, clinicians can accurately classify ptosis severity and guide appropriate management decisions.