What is the diagnosis for a patient with bilateral eye redness, itching, and irritation, accompanied by tearing and normal vision, without pain, photophobia, or purulent discharge?

Diagnosis: Allergic Conjunctivitis

The diagnosis is allergic conjunctivitis (option b), based on the bilateral presentation with prominent itching, tearing, conjunctival injection without ciliary flush, absence of pain or photophobia, and normal visual acuity. 1

Clinical Reasoning Algorithm

Key Diagnostic Features Present

• Bilateral involvement with itching as the predominant symptom - This is the hallmark of allergic conjunctivitis, where itching is usually the most prominent feature when both eyes are affected 1
• Conjunctival injection without ciliary flush - The absence of ciliary flush (limbal injection) effectively rules out anterior uveitis, keratitis, and scleritis, which all produce deeper inflammation 1
• Normal visual acuity and crisp corneal light reflex - This excludes keratitis, which would show corneal involvement with fluorescein staining and typically affects vision 1
• Absence of pain, photophobia, and purulent discharge - These negative findings are critical for excluding infectious, inflammatory, and vision-threatening conditions 1

Systematic Exclusion of Other Diagnoses

Anterior uveitis (option a) is excluded because:

• Uveitis presents with pain, photophobia, and ciliary flush (perilimbal injection) 1
• Visual acuity would typically be reduced 1
• Itching is not a prominent feature of uveitis 1

Keratitis (option c) is excluded because:

• Keratitis causes pain and photophobia as cardinal symptoms 1
• The crisp corneal light reflex indicates no corneal involvement 1
• Fluorescein staining would reveal corneal epithelial defects or infiltrates in keratitis 2
• Contact lens-related keratitis would show punctate epithelial keratopathy or corneal neovascularization 1

Scleritis (option d) is excluded because:

• Scleritis presents with severe, boring pain that may radiate to the face and awaken patients from sleep 1
• Pain with extraocular movements is characteristic of scleritis, which is absent here 1
• The patient reports no pain whatsoever 1

Supporting Evidence for Allergic Conjunctivitis

Classic presentation matches guideline criteria:

• Allergic conjunctivitis produces conjunctival injection and chemosis with itchy eyes and tearing 1
• Both eyes are typically affected, which is the case here 1
• The 2-week duration fits with perennial allergic conjunctivitis, which can be triggered by indoor allergens present year-round 1
• Blurring due to tearing (not true visual impairment) is consistent with allergic conjunctivitis 3

Contact lens consideration:

• While the patient wears contact lenses, she appropriately discontinued them when symptoms started 1
• Contact lens-related keratoconjunctivitis would show papillary hypertrophy of the superior tarsal conjunctiva and corneal changes, not just bilateral conjunctival injection 1
• Giant papillary conjunctivitis from contact lenses typically shows mucoid discharge and superior tarsal papillae, not described here 1

Clinical Pitfalls to Avoid

• Do not assume all bilateral red eyes in contact lens wearers are lens-related - The absence of pain, normal corneal examination, and prominent itching point away from contact lens complications 1
• Always examine the cornea with fluorescein - Though not mentioned in this case, this would definitively exclude keratitis 2
• Itching is the key discriminator - When itching dominates the symptom complex with bilateral involvement and no pain, allergic conjunctivitis is the most likely diagnosis 1, 3