Lagophthalmos

Evidence-based assessment and management of incomplete eyelid closure. Comprehensive guide covering etiology, pathogenesis, classification, diagnosis, and treatment protocols for optometry practice.

Last updated: March 2026

Figure: Dual-panel illustration of lagophthalmos. Left: external presentation showing incomplete upper eyelid closure with the retracted upper lid failing to reach the lower lid, exposing the inferior cornea and conjunctiva (note SPK from exposure keratopathy). The dashed line indicates the expected normal closed lid position. Right: sagittal cross-section demonstrating the tissue layers — skin, weakened orbicularis oculi (CN VII palsy), tarsal plate, and conjunctiva — with the levator/Müller's muscle pathway. The pathological lid-globe gap between the upper lid margin and globe surface results in corneal exposure and tear film disruption.

Lagophthalmos (from Greek: lagos = hare, ophthalmos = eye) refers to the inability to completely close the eyelids, resulting in persistent or intermittent exposure of the ocular surface. The term historically alludes to the ancient observation that hares appeared to sleep with their eyes open. In clinical practice, lagophthalmos is defined as an inter-marginal gap of ≥1 mm during attempted full eyelid closure.

The condition poses significant risk to the ocular surface through inadequate spread of the tear film, insufficient mechanical protection, and chronic epithelial desiccation. Without timely recognition and management, lagophthalmos can progress to exposure keratopathy, infectious keratitis, and permanent corneal scarring with consequent vision loss. It is a frequently underdiagnosed condition, particularly in its nocturnal (sleep-related) form, and demands a systematic approach by the optometrist.

Neurogenic Causes

Facial nerve (CN VII) palsy: Most common cause; paralysis of orbicularis oculi prevents active lid closure. Includes Bell's palsy, Ramsay Hunt syndrome, iatrogenic (parotid surgery), and central lesions
Möbius syndrome: Congenital cranial nerve aplasia affecting CN VI and VII bilaterally
Pontine lesions: Infarct, tumour, or demyelination affecting the CN VII nucleus
Acoustic neuroma: Compression of CN VII in the cerebellopontine angle or internal auditory canal

Mechanical / Structural Causes

Cicatricial eyelid disease: Scarring from chemical or thermal burns, Stevens-Johnson syndrome, trachoma, ocular cicatricial pemphigoid limiting lid excursion
Proptosis / exophthalmos: Thyroid eye disease (most common cause of proptosis-related lagophthalmos), orbital tumours, orbital cellulitis — forward displacement of the globe prevents lid apposition
Ectropion: Outward rotation of the lower lid reduces effective closure and creates an open inferior fissure
Eyelid coloboma: Full-thickness lid defect (congenital or post-traumatic)
Post-surgical: Over-correction of blepharoplasty (upper lid), aggressive lid tumour resection without adequate reconstruction
Symblepharon: Adhesion of palpebral to bulbar conjunctiva restricting lid movement

Nocturnal Lagophthalmos

Physiological nocturnal lagophthalmos: Incomplete eyelid closure during REM sleep, reported in up to 10–20% of healthy individuals; often subclinical
Floppy eyelid syndrome: Lax, rubbery tarsal plates allow the upper lid to evert spontaneously during sleep, leaving the ocular surface exposed
Obstructive sleep apnoea (OSA): Strongly associated with floppy eyelid syndrome; positive airway pressure masks may exacerbate nocturnal exposure

Iatrogenic / Other Causes

General anaesthesia: Incomplete lid closure under sedation with poor tape adherence
Intensive care unit (ICU) exposure keratopathy: Critically ill or unconscious patients with reduced blink and lid tone
Botulinum toxin injection: Iatrogenic orbicularis paresis following periorbital cosmetic treatment
Leprosy (Hansen's disease): CN VII involvement and loss of orbicularis function; historically significant in endemic regions

Normal Eyelid Closure Mechanism

Complete eyelid closure requires coordinated action of the orbicularis oculi muscle (CN VII), lid retractor relaxation (levator palpebrae superioris and Müller's muscle superiorly; capsulopalpebral fascia and inferior tarsal muscle inferiorly), and normal eyelid architecture. Bell's phenomenon — the upward and outward rotation of the globe during attempted closure — provides a partial protective mechanism for the cornea when the lid cannot fully close.

Cascade of Ocular Surface Injury

Incomplete blink and tear film disruption: The blink reflex, which normally renews the precorneal tear film every 5–10 seconds, is diminished. Evaporation accelerates, tear film break-up time shortens, and the mucin layer becomes deficient over the exposed zone
Epithelial desiccation: The inferior third and centre of the cornea — the interpalpebral exposure zone — undergoes progressive desiccation. Superficial punctate epithelial erosions (SPEs) are the earliest finding, typically in an inferior band distribution
Barrier function loss: Disruption of tight junctions in the corneal epithelium compromises the epithelial barrier, allowing pathogen adherence and penetration. Stromal oedema may occur secondary to epithelial breakdown
Inflammatory amplification: Persistent epithelial stress activates pro-inflammatory cascades (IL-1α, IL-6, TNF-α, MMP-9), worsening mucin production and goblet cell density. Neurogenic inflammation from impaired corneal sensation may compound the injury in CN VII palsy, where CN V may also be compromised (cerebellopontine angle lesion, acoustic neuroma)
Microbial superinfection: Desiccated, inflamed epithelium is highly susceptible to bacterial and fungal colonisation. Staphylococcus aureus, Pseudomonas aeruginosa, and opportunistic fungi are frequent pathogens in exposure keratitis
Stromal melting and perforation: In severe or prolonged cases, matrix metalloproteinase-driven stromal lysis leads to progressive corneal thinning, descemetocele formation, and ultimately perforation — an ocular emergency

Role of Bell's Phenomenon

Bell's phenomenon is present in approximately 75% of individuals and confers partial protection by rotating the cornea superiorly behind the lid gap during attempted closure. Absence of Bell's phenomenon (present in ~25% of the population) significantly worsens the prognosis of lagophthalmos, as the central cornea remains fully exposed. Assessing Bell's phenomenon is therefore a critical step in the initial evaluation.

By Aetiology

Neurogenic lagophthalmos: Orbicularis paresis from CN VII dysfunction at any level
Mechanical lagophthalmos: Physical obstruction to lid closure (proptosis, scarring, ectropion, symblepharon)
Cicatricial lagophthalmos: Lid shortening from scarring limiting excursion
Nocturnal (physiological) lagophthalmos: Incomplete closure specific to sleep with daytime closure intact

By Severity of Closure Deficit

Grade	Closure Gap	Corneal Risk	Typical Finding
Mild	1–2 mm	Low (if Bell's present)	Inferior SPEs, mild irritation
Moderate	2–4 mm	Moderate	Confluent epitheliopathy, SPEs, mucous discharge
Severe	>4 mm	High; especially if Bell's absent	Corneal ulceration, stromal haze, risk of perforation

By Onset

Congenital: Coloboma, Möbius syndrome, facial hypoplasia
Acquired: The majority of clinical cases; may be acute (Bell's palsy, trauma) or chronic (thyroid eye disease, cicatricial conditions)

Patient-Related Risk Factors

Diabetes mellitus — increased risk of peripheral and cranial nerve palsies, including CN VII
Hypertension and cardiovascular disease — association with Bell's palsy and brainstem events
Autoimmune conditions — thyroid eye disease (Graves' disease), sarcoidosis, systemic lupus erythematosus
Pregnancy — transient Bell's palsy risk is three times higher in the third trimester
Obesity and OSA — associated with floppy eyelid syndrome and nocturnal lagophthalmos
Herpes virus infection (HSV-1, VZV) — reactivation along CN VII
HIV infection — increased susceptibility to peripheral facial nerve palsy
Age — reduced orbicularis tone and skin laxity increase exposure risk

Factors Worsening Severity

Absent or poor Bell's phenomenon
Concurrent corneal anaesthesia (CN V involvement)
Pre-existing dry eye disease or reduced tear secretion
Low ambient humidity (air conditioning, fans directed at the face)
Contact lens wear in the context of exposure keratopathy
Immunosuppression (systemic steroids, chemotherapy)

Eyelid Signs

Incomplete closure gap: A measurable inter-marginal gap (≥1 mm) on attempted voluntary closure; measured with a ruler or slit lamp graticule
Reduced or absent blink rate: Normal blink rate is 12–20 blinks/min; may be grossly reduced in facial palsy
Widened palpebral aperture at rest (in facial palsy): Loss of orbicularis tone causes the lower lid to sag and the upper lid to be relatively elevated, widening the fissure
Lagophthalmos sign (sleep test): Observing the patient's eyelids 5–10 minutes after they appear asleep (or simulating sleep) reveals persistent inter-marginal gap
Ectropion of lower lid: In chronic facial palsy, the lower lid sags further, exacerbating the closure deficit and causing epiphora
Bell's phenomenon assessment: Ask patient to forcibly close; observe whether the globe rotates upward (positive = protective, negative = high corneal risk)

Ocular Surface Signs

Inferior/interpalpebral superficial punctate epitheliopathy (SPE): The earliest and most consistent sign — fine fluorescein-staining erosions in an inferior band or interpalpebral zone distribution
Reduced or unstable tear film: Shortened tear film break-up time (TBUT); reduced tear meniscus height
Rose bengal or lissamine green staining: Conjunctival staining in the exposed zone, indicating devitalised epithelium and mucus deficiency
Corneal filaments: Mucous strands adhering to desiccated epithelium
Stromal oedema and haze: In moderate to severe cases; may reflect compromised epithelial barrier
Corneal ulceration: Sterile initially; secondary bacterial infiltrate appears as a white/grey stromal opacity
Neovascularisation: Inferior corneal vascularisation in chronic exposure
Reduced corneal sensitivity: Secondary to chronic epithelial denervation or co-existing CN V compromise; tested with cotton wick or Cochet-Bonnet aesthesiometer

Daytime Symptoms

Dryness and foreign body sensation — often the presenting complaint
Burning and stinging, particularly in environments with low humidity, air conditioning, or wind
Photophobia — secondary to corneal epithelial disruption
Epiphora (paradoxical tearing) — reflex lacrimation in response to ocular surface irritation; or punctal ectropion preventing drainage
Blurred or fluctuating vision — irregular tear film over exposed cornea
Mucous discharge — goblet cell dysfunction and secondary inflammation

Nocturnal Symptoms

Severe eye pain or irritation upon waking — a hallmark symptom of nocturnal lagophthalmos; relief within 10–30 minutes of waking as tears re-wet the cornea
Partner reports of sleeping with eyes open (lagophthalmos nocturna)
Progressive accumulation of symptoms through the week, worse on mornings after hot, dry sleeping environments

Clinical note: Patients with concurrent corneal hypoaesthesia (CN V involvement or chronic exposure denervation) may be paradoxically asymptomatic despite significant epithelial disease — a dangerous scenario. Absence of symptoms does not exclude severe lagophthalmos. Always examine the ocular surface irrespective of symptom burden.

Ocular Surface Complications

Exposure keratopathy: Spectrum from mild SPEs to large epithelial defects; may be graded using the Oxford grading scheme or Mackie classification for neurotrophic keratitis overlap
Infectious keratitis: Bacterial (most common), fungal, and rarely Acanthamoeba keratitis superimposed on desiccated/devitalised epithelium; can be rapidly progressive and vision-threatening
Corneal ulceration and stromal melting: MMP-driven keratolysis leads to thinning, descemetocele, and risk of perforation — an ocular emergency requiring immediate referral
Permanent corneal scarring: Subepithelial and stromal opacification causing irreversible visual loss
Corneal neovascularisation: Inferior pannus formation from chronic exposure and inflammation
Band keratopathy: Calcium deposition in Bowman's layer following prolonged inflammation

Long-Term Sequelae

Reduced best-corrected visual acuity (BCVA): From corneal scarring, irregular astigmatism, or corneal thinning
Chronic pain and photophobia: Corneal neuropathic pain following recurrent epithelial breakdown
Chronic secondary dry eye disease: Permanent goblet cell loss and lacrimal gland dysfunction
Endophthalmitis: Rare but catastrophic extension of infectious keratitis into the anterior chamber and vitreous

Urgent referral indicators: Corneal ulceration with white infiltrate, corneal thinning >50% stromal depth, descemetocele formation, or perforation requires same-day ophthalmology referral. Do not patch an infected eye or a suspected corneal ulcer.

Systemic Diseases Associated with Lagophthalmos

Condition	Mechanism	Additional Ocular Features
Graves' disease / TED	Proptosis, lid retraction (Müller's spasm)	Optic neuropathy, restrictive strabismus, chemosis
Bell's palsy	Idiopathic CN VII palsy (HSV reactivation implicated)	Reduced corneal sensation if severe; stapedius reflex loss
Ramsay Hunt syndrome (VZV)	CN VII + geniculate ganglion involvement	Herpetic vesicles on pinna/palate; hearing loss; CN V overlap
Sarcoidosis	Granulomatous CN VII palsy; lacrimal gland infiltration	Uveitis, optic nerve granuloma, dry eye
Lyme disease (Borrelia burgdorferi)	Bilateral or unilateral CN VII palsy	Uveitis, optic neuritis, keratitis
Leprosy (Hansen's disease)	CN VII dermal infiltration; orbicularis atrophy	Corneal hypoaesthesia (CN V); interstitial keratitis
Stroke / intracranial tumour	UMN or LMN CN VII palsy depending on lesion level	Hemianopia, gaze palsy, diplopia
OSA / Floppy eyelid syndrome	Lid laxity, nocturnal exposure	Papillary conjunctivitis, keratoconus association

Red Flags Requiring Systemic Workup

New-onset CN VII palsy without obvious cause — must exclude otitis media, parotid malignancy, cholesteatoma, acoustic neuroma, Lyme disease, sarcoidosis, and brainstem lesion
Bilateral facial palsy — strongly warrants systemic investigation (Lyme, sarcoid, Guillain-Barré)
Recurrent ipsilateral CN VII palsy — consider Melkersson-Rosenthal syndrome or parotid pathology
Progressive or painless proptosis — thyroid function tests (TSH, FT4, anti-TSH receptor antibody), orbital imaging mandatory
Facial palsy + hearing loss + vesicular rash — Ramsay Hunt; requires urgent antiviral therapy within 72 hours of onset

Clinical History

Onset and duration of facial weakness or lid closure deficit
Preceding viral illness, ear pain, vesicular rash (Ramsay Hunt), recent surgery, trauma
Morning eye pain or irritation worse upon waking (nocturnal lagophthalmos)
Partner-reported sleeping with eyes open
History of thyroid disease, autoimmune conditions, malignancy, OSA
Medications: botulinum toxin, chemotherapy, systemic steroids
Previous eyelid, orbital, or parotid surgery

Clinical Examination Protocol

Lid closure measurement: Ask the patient to close their eyes gently and fully. Measure the inter-marginal gap with a ruler or slit lamp graticule in millimetres. Repeat with forced closure
Bell's phenomenon: Ask the patient to close the eyes with examiner's fingers providing slight resistance; observe direction of globe rotation
Palpebral aperture width: Measure vertical height in primary gaze (normal 9–11 mm). Widened aperture may indicate orbicularis weakness or lid retraction
Lid laxity assessment: Snap-back test and distraction test for the lower lid; for upper lid, assess resistance to inferior displacement
Corneal sensation: Wisp of cotton or Cochet-Bonnet aesthesiometer in each corneal quadrant; compare inter-eye and within quadrants
Fluorescein staining: Install 2% sodium fluorescein; examine under cobalt blue illumination with Wratten 12 filter. Grade SPEs using Oxford grading scale (0–V) or NEI grading. Note distribution: inferior band = exposure pattern
Lissamine green or rose bengal staining: For conjunctival devitalised cells and mucus strands
Tear film assessment: TBUT (normal >10 s; reduced in exposure keratopathy); Schirmer's test if tear secretion in question
Anterior segment biomicroscopy: Assess corneal clarity, stroma, Descemet's membrane, and anterior chamber; rule out infiltrate or hypopyon
Proptosis assessment: Exophthalmometry (Hertel exophthalmometer) if thyroid eye disease or orbital mass suspected; normal proptosis ≤21 mm; inter-eye asymmetry >2 mm is significant

Grading of Exposure Keratopathy Severity

Stage	Findings	Action
1 — Mild SPE	Fine inferior punctate staining, no epithelial defect	Intensify lubrication; monitor
2 — Confluent SPE / filaments	Coalescent staining, mucous filaments, reduced TBUT	Lubrication + lid taping nocturnal; consider referral
3 — Epithelial defect	Frank epithelial erosion, no stromal haze	Urgent same-week ophthalmology referral; therapeutic CL or moisture chamber
4 — Stromal involvement / ulcer	Stromal haze, thinning, infiltrate, or perforation risk	Same-day emergency referral

Ancillary Investigations

Corneal topography / tomography: Assess for keratoconus (association with floppy eyelid syndrome), irregular astigmatism from scarring, or steepening from chronic inflammation
Anterior segment OCT: Epithelial mapping and stromal thickness assessment in exposure keratopathy; detect subclinical corneal thinning
Anterior segment photography: Document progression of epitheliopathy at each visit using the slit lamp camera
Meibography: In cases with concurrent meibomian gland dysfunction contributing to evaporative dry eye
Hertel exophthalmometry: Quantify proptosis and monitor TED-related lagophthalmos progression
Imaging (MRI/CT orbits): Ordered by ophthalmologist or neurologist; indicated for suspected orbital mass, acoustic neuroma, or brainstem lesion
Blood tests: Thyroid function (TSH, FT4, TRAb), ACE level (sarcoidosis), Borrelia serology (Lyme), FBC (inflammatory markers) — directed by clinical suspicion

Lubrication (First-Line in All Cases)

Preservative-free artificial tears: High-viscosity formulations preferred for exposure keratopathy (e.g., hyaluronic acid 0.2–0.4%, carboxymethylcellulose 1%, polyacrylic acid gels). Dosing every 1–2 hours in symptomatic daytime exposure; every 30 minutes in severe cases
Lubricating eye ointment (nocturnal): Paraffin-based ointment (e.g., Lacri-Lube, VitA-POS) applied at bedtime; provides sustained moisture during sleep. Essential in all forms of lagophthalmos. Counsel patients on transient blur after application
Autologous serum eye drops: 20–50% concentration; contains EGF, fibronectin, and vitamin A; indicated in persistent epithelial defect or neurotrophic overlap unresponsive to conventional lubrication

Mechanical Ocular Surface Protection

Eyelid taping: Micropore or transpore surgical tape applied to gently close the lids at night; must not compress the globe. Technique: one horizontal strip across the full upper lid margin to lower lid; instruct patient to remove immediately if discomfort. Skin preparation with barrier cream reduces maceration
Moisture chamber glasses/goggles: Wrap-around protective eyewear with side shields maintains periocular humidity; useful for daytime and sleep; commercially available options (e.g., EyeEco, 7Eye Airshield). Particularly valuable in Bell's palsy during recovery phase
Bandage contact lens (BCL): High-Dk silicone hydrogel extended-wear BCL provides mechanical epithelial coverage and reduces pain in persistent epithelial defects. Use only under close surveillance (monitor for infectious keratitis); requires concurrent broad-spectrum antibiotic prophylaxis (e.g., ofloxacin 0.3% QID or moxifloxacin 0.5% QID). Not suitable for home-initiated use without ophthalmology review in severe cases
Scleral lenses: For cases with severe ocular surface disease or irregular cornea; maintain a fluid reservoir over the corneal surface; fitted and managed with specialist optometry or ophthalmology co-management

Adjunctive Medical Management

Topical antibiotics: Indicated if secondary bacterial infection or prophylactically with BCL. Not routinely required for simple exposure keratopathy
Low-dose topical corticosteroids: Short-term (fluorometholone 0.1% QID for 1–2 weeks) to suppress surface inflammation; use judiciously — contraindicated if epithelial defect present or infection suspected. Initiated and monitored by optometrist with prescribing authority or ophthalmologist
Ciclosporin 0.05% (topical immunomodulator): For chronic inflammatory dry eye component in lagophthalmos; adjunct to artificial tears; long-term use
Systemic treatment of underlying cause: Oral prednisolone for Bell's palsy (within 72 h of onset per NICE guidelines); antiviral therapy for Ramsay Hunt (within 72 h); methimazole/carbimazole and/or immunosuppression for TED; antibiotics for Lyme disease
Neurotrophic keratitis targeted therapy: Cenegermin (recombinant human nerve growth factor, Oxervate) — indicated for persistent neurotrophic epithelial defect in stage 2–3 neurotrophic keratitis where neurotrophic component co-exists with lagophthalmos

Surgical Management (Ophthalmology)

Temporary tarsorrhaphy: Suturing the lateral lids together to narrow the aperture; effective, reversible bridge while awaiting nerve recovery or definitive correction. Reduces exposure surface without impairing central vision significantly
Permanent lateral tarsorrhaphy: For permanent lagophthalmos where recovery is not anticipated; reduces fissure width
Gold weight implant (upper lid): Titanium or gold weight placed in the upper lid pre-tarsal plane; gravity aids closure; does not affect voluntary opening; 1.0–1.8 g weights typically used; weight sizing based on lid closure deficit
Palpebral spring implant: Dynamic spring mechanism aids passive closure; technically demanding; indicated when gold weight insufficient (supine patients, Bell's phenomenon absent)
Lower lid elevation procedures: Lateral tarsal strip for lower lid ectropion exacerbating lagophthalmos; spacer graft (palatal mucosa, donor sclera) for cicatricial lower lid retraction
Amniotic membrane transplantation: For persistent epithelial defects and ocular surface reconstruction
Orbital decompression: For TED-related lagophthalmos from significant proptosis — removes orbital wall fat/bone to allow globe to recess
Botulinum toxin to levator (ptosis induction): Temporary, useful in acute severe Bell's palsy or postoperative exposure; induces reversible ptosis to protect the cornea

Singapore Optometry Scope Note

Optometrists in Singapore may initiate and monitor lubrication therapy, lid taping, and moisture chambers within their scope of practice. Bandage contact lenses may be fitted with appropriate clinical oversight; antibiotic prophylaxis should be co-prescribed with the supervising ophthalmologist where required. Diagnostic equipment such as the slit lamp (with fluorescein), corneal topographer, anterior segment OCT, and Hertel exophthalmometer are appropriate for the optometrist's role in monitoring disease progression and ocular surface status — fundus assessment requires specialist referral to ophthalmology rather than dilation by the optometrist. All surgical interventions and prescribing of topical steroids, cenegermin, or autologous serum drops require ophthalmology collaboration or referral. Timely and appropriately detailed referral letters are essential; document closure gap measurement, Bell's phenomenon status, fluorescein grading, and TBUT at each visit to facilitate ophthalmology triage.

Prognosis by Aetiology

Bell's palsy: Approximately 71% of patients recover complete facial function within 6 months with appropriate systemic treatment. Incomplete recovery (residual lagophthalmos) occurs in 15–30%; synkinesis may complicate recovery. Earlier steroid initiation and younger age are positive predictors
Ramsay Hunt syndrome: Prognosis is worse than Bell's palsy — complete recovery in only 50–60% of cases even with antiviral and steroid therapy. Bilateral hearing loss may be permanent. High risk of residual lagophthalmos requiring surgical correction
Thyroid eye disease (TED): Prognosis depends on control of underlying thyroid disease and timely immunosuppression (IV methylprednisolone) during the active inflammatory phase. Orbital decompression and lid-lengthening procedures provide good functional outcomes in the quiescent phase
Nocturnal / physiological lagophthalmos: Excellent prognosis with conservative measures (ointment, taping); rarely requires surgical intervention
Traumatic and iatrogenic (surgical): Variable; depends on extent of tissue loss, quality of reconstruction, and residual motor function. Gold weight implants have 85–95% patient satisfaction rates for paralytic lagophthalmos
Leprosy-related: Lagophthalmos often permanent in advanced disease; requires long-term surgical and ocular surface management in endemic settings

Factors Affecting Visual Prognosis

Presence and quality of Bell's phenomenon — the single most important protective factor
Integrity of corneal sensation — anaesthetic cornea dramatically worsens epithelial healing capacity
Severity and duration of exposure before treatment initiation
Adequacy of lubrication adherence and nocturnal protection
Early surgical intervention (tarsorrhaphy, gold weight) in high-risk cases before irreversible corneal damage occurs
Avoidance of superimposed infection through patient education and appropriate follow-up frequency

1. Exposure Keratopathy Without Lagophthalmos

Features: Inferior SPEs, reduced TBUT, dry eye symptoms
Key difference: Lid closure is complete; corneal exposure due to reduced blink rate, aqueous deficiency, or meibomian gland dysfunction — not lid gap
Clue: Normal interpalpebral gap measurement on attempted closure

2. Neurotrophic Keratitis (NK)

Features: Persistent epithelial defect, smooth edges, reduced corneal sensitivity
Key difference: NK arises from CN V denervation without necessarily having a lid closure deficit; however, CN V and CN VII may co-exist in lesions of the cerebellopontine angle
Clue: Dramatically reduced or absent corneal sensation is the diagnostic hallmark of NK; lagophthalmos-related keratopathy may have near-normal sensation initially

3. Lid Retraction (Thyroid Eye Disease)

Features: Upper lid margin above the superior limbus, scleral show, staring appearance; lagophthalmos may or may not be present
Key difference: Lid retraction is characterised by abnormally elevated upper lid; may cause lagophthalmos but the primary defect is lid position, not orbicularis function
Clue: Lid lag on downgaze (Von Graefe's sign), proptosis, and systemic thyroid symptoms

4. Ectropion

Features: Outward rotation of the lower lid, punctal eversion, epiphora, conjunctival exposure
Key difference: Ectropion is a lid positional anomaly, not primarily a closure deficit; however severe ectropion can prevent effective lower lid apposition and thus contribute to lagophthalmos
Clue: The lower lid margin is visibly everted; not simply lagging on closure

5. Symblepharon

Features: Adhesion bands between palpebral and bulbar conjunctiva restricting lid and globe movement
Key difference: Mechanical restriction of lid closure due to conjunctival fibrosis; often cicatricial in origin (SJS, OCP, chemical burn). The lid itself may be structurally normal

Diagnostic Comparison Table

Condition	Closure Gap	Orbicularis	Key Distinguishing Feature
Lagophthalmos	Present (≥1 mm)	Weak / paralysed or mechanically limited	Incomplete lid closure is primary finding
Exposure keratopathy (no lag)	Absent	Normal	Reduced blink/aqueous deficiency/MGD
Neurotrophic keratitis	Variable	Normal or reduced (if CN VII also affected)	Reduced corneal sensation; smooth-edged persistent defect
Lid retraction (TED)	May be present	Normal (lid retracted, not weak)	Upper lid above superior limbus; proptosis; lid lag
Ectropion	May contribute	Normal or reduced (if combined facial palsy)	Lower lid everted; punctal ectropion; epiphora

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Clinical Illustration

Overview

Etiology