Anterior Segment and Adnexal Disease
Anterior segment items test pattern recognition and safe triage of the red eye. The examiner wants to know whether you can separate benign, self-limiting disease from sight-threatening or life-threatening disease.
Red eye triage
Differentiate by discharge (watery, mucoid, purulent), vessels (conjunctival movers vs ciliary flush), corneal involvement (fluorescein, Seidel), anterior chamber reaction (cells and flare), pupil, and intraocular pressure. Reduced acuity, ciliary flush, photophobia, and pain suggest corneal or intraocular disease, not simple conjunctivitis. Grade cells and flare; large greasy keratic precipitates indicate granulomatous uveitis.
Common and dangerous entities
Anterior blepharitis is staphylococcal and responds to lid hygiene; posterior blepharitis is meibomian gland dysfunction. Hordeolum is acute and tender; chalazion is chronic and granulomatous. Dacryocystitis presents below the medial canthus with tearing; dacryoadenitis above it with an S-shaped lid. Preseptal cellulitis spares eye movement; orbital cellulitis causes proptosis, pain on movement, and restricted motility and needs urgent imaging and IV antibiotics. Dendritic staining indicates herpes simplex; a contact lens wearer with a stromal infiltrate has bacterial keratitis until cultured otherwise.
Worked example
A 24-year-old soft lens wearer has a painful red right eye, photophobia, acuity 20/60, a 2 mm paracentral infiltrate with overlying epithelial defect, and a 1 mm hypopyon. Reasoning: microbial keratitis. Discontinue lens wear, obtain corneal scrapings for a central or large lesion, start topical fluoroquinolone hourly around the clock, and follow daily. Patching is contraindicated; adding steroid without antimicrobial coverage is unsafe.
Traps
Prescribing a steroid for an undiagnosed red eye; missing orbital signs in "cellulitis"; patching a corneal ulcer; and treating a dendritic ulcer with steroid alone.