What is a common cause of unilateral eye swelling without trauma or vision impairment?

Common Causes of Unilateral Eye Swelling Without Trauma or Vision Impairment

The most common causes of unilateral eye swelling without trauma or vision impairment are viral conjunctivitis (particularly adenoviral), allergic reactions/angioedema, and chalazion, with viral conjunctivitis being the most frequent infectious etiology in this presentation. 1, 2

Most Likely Diagnoses

Viral Conjunctivitis (Adenoviral)

• Adenoviral conjunctivitis classically presents with unilateral eyelid swelling and erythema, often progressing to sequential bilateral involvement within days. 1
• Accompanied by watery discharge, bulbar conjunctival injection, chemosis, and follicular reaction of the inferior tarsal conjunctiva. 1
• Associated with recent exposure to infected individuals (especially in school or healthcare settings) or concurrent upper respiratory infection. 1
• Self-limited course with improvement within 5-14 days without treatment. 1
• Can resemble orbital cellulitis on examination due to significant eyelid swelling and erythema, but lacks proptosis and restricted eye movements. 1

Allergic Reaction or Angioedema

• Unilateral angioedema can present with isolated eyelid swelling, often with chemosis but minimal pain or redness. 2, 3
• History typically reveals new exposures to foods, medications (particularly NSAIDs), insect bites, or environmental allergens. 2, 3
• May involve conjunctival congestion and can persist for several hours to days. 3
• Responds to antihistamines and oral corticosteroids if severe. 2, 3

Chalazion

• Presents as firm nodule within the tarsal plate, which may cause diffuse eyelid swelling even without obvious external inflammation. 2
• Can be subtle on external examination but palpable on careful eyelid examination. 2

Critical Red Flags Requiring Immediate Evaluation

Rule Out Vision-Threatening Conditions

• Perform fluorescein staining in every case to detect corneal involvement, which is mandatory even when vision appears normal. 2
• Examine for eyelid vesicles or dermatomal rash suggesting herpes simplex or varicella zoster, which can progress to keratitis, corneal scarring, and perforation. 1, 2
• Check for purulent discharge that rapidly reaccumulates after cleaning, indicating possible gonococcal conjunctivitis requiring immediate ophthalmology referral. 2
• Assess for proptosis or restricted eye movements indicating orbital cellulitis or orbital mass, even without obvious redness. 2, 4

Herpes Simplex Virus (HSV) Conjunctivitis

• Usually unilateral with bulbar conjunctival injection, watery discharge, and mild follicular reaction. 1
• Distinctive signs include vesicular rash or ulceration of eyelids and dendritic epithelial keratitis. 1
• Can progress to corneal edema, stromal keratitis, scarring, perforation, and uveitis if untreated. 1

Varicella Zoster Virus (VZV)

• Presents with unilateral bulbar conjunctival injection, watery discharge, and follicular reaction. 1
• Vesicular dermatomal rash or eyelid ulceration with severe pain is characteristic. 1
• Can lead to corneal scarring, late corneal anesthesia, dry eye, and retinitis. 1

Less Common But Important Diagnoses

Epstein-Barr Virus (EBV)

• Follicular conjunctivitis, typically unilateral with ipsilateral lymphadenopathy. 1
• Can present with hemorrhagic conjunctivitis and periorbital edema. 1
• Associated with systemic signs including fatigue, fever, pharyngitis, and splenomegaly. 1

Molluscum Contagiosum

• Typically unilateral with mild to severe follicular reaction. 1
• Distinctive dome-shaped umbilicated lesion(s) on eyelid skin or margin. 1
• Chronic follicular conjunctivitis associated with eyelid lesions that can persist for months to years. 1

Conjunctival Lymphoma

• Unilateral, painless, pink "salmon patch" conjunctival swelling on superior or inferior conjunctiva. 1
• Often presents with chronic palpebral or bulbar follicles. 1
• Associated with immune deficiency, autoimmune conditions (Sjögren's, Hashimoto's, IgG4-related disease), and chronic infections. 1

Practical Management Algorithm

Initial Examination

• Perform focused examination looking for vesicular lesions, proptosis, corneal involvement with fluorescein, and purulent discharge. 2
• Palpate eyelid for firm nodule suggesting chalazion. 2
• Check for preauricular lymphadenopathy suggesting viral etiology. 1

Conservative Management (If No Red Flags)

• Trial of cool compresses for symptomatic relief. 2
• Consider antihistamine if allergic etiology suspected based on exposure history. 2
• Mandatory follow-up in 3-4 days to assess for improvement. 2

When to Refer to Ophthalmology

• Immediate referral required for any visual changes, moderate to severe pain, corneal involvement on fluorescein examination, or suspected HSV/VZV. 2
• Persistent swelling beyond 3-4 days without improvement despite appropriate treatment requires orbital imaging (CT or MRI) and ophthalmology referral. 2

Common Pitfalls to Avoid

• Failing to differentiate orbital cellulitis from preseptal cellulitis or viral conjunctivitis—orbital cellulitis requires emergency management to prevent vision loss and intracranial complications. 4
• Missing early HSV or VZV infection before vesicles appear, which can rapidly progress to corneal involvement. 1, 2
• Overlooking conjunctival lymphoma in cases of persistent unilateral follicular conjunctivitis that fails to resolve. 1, 5