Defining Ptosis of the Eyelids
Ptosis is diagnosed when the upper eyelid margin is positioned lower than normal, typically defined as the margin-to-reflex distance (MRD-1) being less than 4 mm or when the upper eyelid covers more than 2 mm of the cornea. 1
Quantitative Classification
Ptosis severity is graded based on the degree of eyelid drooping:
- Minimal ptosis: 1-2 mm of lid droop 1
- Moderate ptosis: 3-4 mm of lid droop 1
- Severe ptosis: Greater than 4 mm, potentially covering the pupil entirely 1
The measurement is typically made by assessing the vertical distance between the upper eyelid margin and the corneal light reflex in primary gaze position. 1
Age-Specific Diagnostic Considerations
In Children
Congenital ptosis is present at birth or appears by 1 year of age and is characterized by drooping of the upper eyelid that persists if untreated. 2, 3
- Most orbital/periorbital plexiform neurofibromas (OPPN) are identified within the first few years of life, with initial identification typically occurring before 5 years of age 4
- Blepharoptosis has an incidence of nearly 100% in children with OPPN 4
- An infant or young child presenting with periorbital asymmetry or unilateral proptosis should be evaluated for OPPN 4
In Adults
Acquired ptosis appears later in life and is the predominant form of the condition encountered in clinical practice. 5
- The unilateral or bilateral drooping of the upper eyelid can affect appearance and impair visual function, negatively impacting quality of life 5
- Ptosis may be due to myogenic, neurogenic, aponeurotic, mechanical, or traumatic causes 1, 6
Critical Clinical Examination Elements
When evaluating suspected ptosis, the American Academy of Ophthalmology recommends specific assessments:
- Pupillary examination: Evaluate for anisocoria and pupillary responses in both bright and dim illumination to identify potential neurological deficits 7
- Levator function assessment: Measure the strength of the levator palpebrae superioris muscle, which helps determine etiology and surgical approach 1, 6
- Complete sensorimotor examination: Detect any associated strabismus 8, 7
- Slit-lamp examination: Identify mechanical causes of ptosis 8, 7
Common Pitfalls to Avoid
Missing pupil-involving third nerve palsy is a critical error, as this can represent a neurosurgical emergency requiring urgent evaluation for compressive lesions, especially posterior communicating artery aneurysm. 8, 7
- Overlooking variable ptosis that worsens with fatigue may indicate myasthenia gravis; perform an ice test or rest test when this presentation is suspected 8, 7, 9
- Failing to recognize that ptosis with mydriasis suggests an intracranial aneurysm, while ptosis with miosis suggests Horner's syndrome (potentially secondary to carotid dissection) 6
- In congenital ptosis, not correcting significant cases promptly can lead to amblyopia and permanently poor vision 2, 1
Associated Findings Requiring Further Evaluation
Ptosis accompanied by the following warrants additional investigation:
- Proptosis or orbital mass: Requires MRI orbits without and with contrast 7
- Neurological symptoms: Consider brainstem pathology; MRI head and orbits without and with contrast is recommended 7
- Floppy eyelid syndrome: Presents with upper eyelid edema and easily everted upper eyelid 8, 7, 9
- Papillary conjunctivitis: May be associated with conditions like giant papillary conjunctivitis 8, 9