Ophthalmology · External Eye Disease
The facts most likely to be tested
Allergic conjunctivitis presents with hallmark bilateral ocular pruritus and conjunctival injection.
Physical examination reveals cobblestone papillae on the superior tarsal conjunctiva in chronic or severe cases.
The pathophysiology is a Type I hypersensitivity reaction mediated by IgE-dependent mast cell degranulation.
Patients frequently report a history of atopy, including allergic rhinitis, asthma, or atopic dermatitis.
Chemosis (conjunctival swelling) is a common clinical finding resulting from increased vascular permeability.
First-line pharmacologic therapy consists of topical antihistamines or mast cell stabilizers such as olopatadine.
The presence of purulent discharge or preauricular lymphadenopathy should prompt consideration of bacterial or viral etiologies instead.
Vignette unlocked
A 22-year-old male presents to the clinic complaining of persistent bilateral eye itching and redness for the past three days. He reports a history of seasonal allergies and notes that his symptoms worsen when he is outdoors. On physical examination, there is bilateral conjunctival injection and mild chemosis. Eversion of the upper eyelids reveals cobblestone papillae on the superior tarsal conjunctiva. Visual acuity is 20/20 bilaterally, and there is no purulent discharge.
What is the most appropriate initial pharmacologic management for this patient?
Topical antihistamine/mast cell stabilizer (e.g., olopatadine)
The patient's presentation of bilateral pruritus, history of atopy, and cobblestone papillae is diagnostic of allergic conjunctivitis, which is best managed with topical antihistamines or mast cell stabilizers.
Full handout
High yield triage
Etiology / Epidemiology
Common in patients with atopy (asthma, eczema, allergic rhinitis). Triggered by airborne allergens like pollen or dander.
Clinical Manifestations
Bilateral pruritus is the hallmark. Look for cobblestoning of the tarsal conjunctiva and chemosis.
Diagnosis
Primarily a clinical diagnosis. No specific lab testing required for routine cases.
Treatment
First-line is topical antihistamines/mast cell stabilizers (e.g., olopatadine). Avoid long-term topical steroids.
Prognosis
Self-limiting but recurrent. Vision loss is extremely rare.
Full handout
Epidemiology & Etiology
Highly prevalent in patients with a history of atopic triad. Seasonal exacerbations correlate with pollen counts and environmental exposure. It is a type I hypersensitivity reaction.
Pertinent Anatomy
The conjunctiva is a thin, vascularized mucous membrane covering the sclera and inner eyelids. The tarsal conjunctiva is the primary site for inflammatory changes like cobblestoning.
Pathophysiology
Allergen exposure triggers IgE-mediated mast cell degranulation. This releases histamine and inflammatory mediators, causing rapid vasodilation and vascular permeability. Chronic inflammation leads to the recruitment of eosinophils and lymphocytes.
Clinical Manifestations
Patients present with intense bilateral pruritus, tearing, and redness. Physical exam reveals cobblestoning (papillary hypertrophy) of the upper tarsal conjunctiva and chemosis (conjunctival swelling). Red flags include vision loss, photophobia, or severe pain, which suggest corneal involvement or alternative diagnoses.
Diagnosis
Diagnosis is clinical based on history of atopy and classic symptoms. No gold standard diagnostic test is required. If symptoms are atypical, referral for conjunctival scrapings may reveal eosinophils.
Treatment
First-line therapy includes topical antihistamine/mast cell stabilizer combinations like olopatadine. Cold compresses and artificial tears provide symptomatic relief. Topical corticosteroids should be avoided due to risks of glaucoma and cataracts.
Prognosis
Condition is benign and self-limiting. 100% of patients should be counseled on allergen avoidance. Monitor for secondary bacterial infection if the patient exhibits excessive rubbing.
Differential Diagnosis
Viral Conjunctivitis: Preauricular lymphadenopathy and watery discharge
Bacterial Conjunctivitis: Purulent discharge and matted eyelids
Dry Eye Syndrome: Gritty, sandy sensation without significant pruritus
Blepharitis: Crusting at the eyelid margins
Keratitis: Significant photophobia and decreased visual acuity