Unilateral Eye Swelling Without Trauma or Vision Impairment

Most Likely Diagnoses

The American Academy of Ophthalmology recommends considering viral conjunctivitis, particularly adenoviral, as the most frequent infectious etiology in unilateral eye swelling without trauma or vision impairment, which classically presents with unilateral eyelid swelling and erythema, often progressing to sequential bilateral involvement within days 1, 2, 3.
Viral conjunctivitis is accompanied by watery discharge, bulbar conjunctival injection, chemosis, and follicular reaction of the inferior tarsal conjunctiva, and is associated with recent exposure to infected individuals or concurrent upper respiratory infection 1, 2, 3.
The American Academy of Ophthalmology notes that viral conjunctivitis has a self-limited course with improvement within 5-14 days without treatment 1, 2, 3.

The American Academy of Ophthalmology recommends performing fluorescein staining in every case to detect corneal involvement, which is mandatory even when vision appears normal, to rule out vision-threatening conditions 4.
Examination for eyelid vesicles or dermatomal rash suggesting herpes simplex or varicella zoster is crucial, as these conditions can progress to keratitis, corneal scarring, and perforation 2, 3, 4.

The American Academy of Ophthalmology notes that Epstein-Barr virus (EBV) can cause follicular conjunctivitis, typically unilateral with ipsilateral lymphadenopathy, and can present with hemorrhagic conjunctivitis and periorbital edema 1.
Molluscum contagiosum typically presents with mild to severe follicular reaction, and distinctive dome-shaped umbilicated lesion(s) on eyelid skin or margin 2, 5.

The American Academy of Ophthalmology recommends a trial of cool compresses for symptomatic relief, and consideration of antihistamine if allergic etiology is suspected based on exposure history 4.
Mandatory follow-up in 3-4 days to assess for improvement is recommended, and immediate referral to ophthalmology is required for any visual changes, moderate to severe pain, corneal involvement on fluorescein examination, or suspected HSV/VZV 4.