What is Ocular Ptosis
Ocular ptosis (blepharoptosis) is drooping of the upper eyelid to a lower than normal position, resulting in vertical narrowing of the palpebral fissure. 1
Definition and Severity Classification
Ptosis is classified by the degree of eyelid drooping 1:
- Minimal ptosis: 1-2 mm of drooping
- Moderate ptosis: 3-4 mm of drooping
- Severe ptosis: >4 mm of drooping, potentially covering the pupil entirely
The condition can affect one eye (unilateral) or both eyes (bilateral). 1
Types of Ptosis
Ptosis is categorized as either congenital (present at birth or diagnosed within the first year of life) or acquired (developing later in life). 1, 2
Etiologic Categories
The underlying causes of ptosis fall into several mechanistic categories 1, 3:
- Myogenic: Related to muscle dysfunction
- Neurogenic: Related to nerve dysfunction affecting the levator palpebrae or cranial nerve III
- Aponeurotic: Related to levator aponeurosis dehiscence or disinsertion (most common acquired form)
- Mechanical: Related to mass effect or structural abnormalities (such as orbital/periorbital plexiform neurofibromas in neurofibromatosis type 1, which cause ptosis in nearly 100% of cases) 4
- Traumatic: Related to injury
Clinical Presentation and Impact
Beyond the visible drooping, patients experience functional and quality of life impairments 1:
- Visual symptoms: Blurred vision, visual field obstruction
- Compensatory mechanisms: Chin-up head position, manually lifting the eyelid with fingers, eyebrow elevation
- Secondary symptoms: Tension headaches and eyestrain from continuous forehead/scalp muscle activation, increased tearing, tired appearance
- Amblyopia risk: If congenital ptosis is not corrected in children, permanent vision loss can develop 1
Key Clinical Examination Findings
A complete sensorimotor examination should be performed to detect any associated strabismus, and a slit-lamp examination should be conducted to identify mechanical causes of ptosis. 5
Critical measurements for establishing the diagnosis include 3:
- Palpebral fissure height
- Marginal reflex distance
- Upper eyelid crease position
- Levator function test
Additional assessments include evaluation for floppy eyelid syndrome (upper eyelid edema with easily everted upper eyelid), papillary conjunctivitis, and horizontal lid laxity. 5
Critical Diagnostic Pitfalls
Clinicians should be aware of the potential for missing pupil-involving third nerve palsy, which can represent a neurosurgical emergency. 5 Do not assume pupil-sparing indicates benign microvascular disease when ophthalmoplegia is complete or bilateral—compressive lesions including posterior communicating artery aneurysm can present this way and require urgent neuroimaging. 6
Overlooking variable ptosis that worsens with fatigue, which may indicate myasthenia gravis, is a common pitfall to avoid. 5 Variable strabismus and ptosis that worsen with fatigue and improve with rest are pathognomonic for myasthenia. 6