Viral keratitis

Conjunctivitis is inflammation of the conjunctiva from viral, bacterial, or allergic causes presenting with red eye, discharge, and preserved vision, diagnosed clinically by discharge character and managed with supportive care, targeted topical antibiotics, or topical antihistamine/mast-cell-stabilizer therapy.

Herpes simplex keratitis is reactivation of latent HSV along the trigeminal nerve causing a corneal dendritic ulcer with pain, photophobia, and decreased corneal sensation. Diagnosis is clinical on slit lamp with fluorescein staining; treatment is a topical or oral antiviral, and topical corticosteroids are contraindicated in active epithelial disease.

Bacterial keratitis is a corneal epithelial and stromal infection, most often Pseudomonas or Staphylococcus in soft contact lens wearers, that is a sight-threatening emergency treated with same-day corneal culture followed by hourly topical moxifloxacin 0.5% (small ulcer) or alternating fortified vancomycin and tobramycin (large or central ulcer). Delay or misdiagnosis as a benign red eye risks stromal melt, perforation, and permanent vision loss.

Acanthamoeba keratitis is a corneal infection by a free-living amoeba, strongly linked to soft contact lens wear combined with freshwater exposure, diagnosed by microscopic examination of corneal scrapings and treated with prolonged topical antiamoebic/antifungal therapy that often fails to prevent progressive corneal destruction. Any contact lens wearer with a painful, non-healing keratitis that is not responding to antibacterial therapy needs this diagnosis considered and an urgent corneal scraping sent.

Microbial keratitis (infectious corneal ulcer) is the unifying vision-threatening syndrome of a painful red eye with a corneal infiltrate, produced by bacterial, viral, fungal, or amebic invasion of a breached corneal epithelium, managed by the same urgent pathway regardless of organism: emergent scraping for smear and culture before any drug is given, then broad empiric coverage narrowed once results return. Delay, misdiagnosis as simple conjunctivitis, or premature corticosteroid use converts a treatable ulcer into stromal melt, perforation, and permanent vision loss.

A corneal abrasion is a traumatic or foreign-body-related defect of the corneal epithelium diagnosed by fluorescein uptake under cobalt-blue light. Uncomplicated cases heal in days with lubrication and pain control, but contact-lens wear mandates antipseudomonal coverage and any red flag (rust ring, infiltrate, Seidel sign, hypopyon) demands same-day ophthalmology referral.

Endophthalmitis is a vision-threatening suppurative infection of the aqueous and vitreous humors, most often exogenous after cataract or other intraocular surgery and less often endogenous from hematogenous seeding during bacteremia or candidemia. Diagnosis is clinical, confirmed by vitreous/aqueous tap, and treatment is emergent intravitreal antibiotics or antifungals with vitrectomy for severe cases.

Ophthalmia neonatorum is conjunctivitis presenting in the first month of life, caused by chemical irritation, Neisseria gonorrhoeae, Chlamydia trachomatis, or herpes simplex virus acquired at delivery. Age of onset and discharge character point to the organism, and treatment is organism-specific because gonococcal and herpetic disease can destroy the eye within days.

Herpes zoster ophthalmicus is reactivation of latent varicella-zoster virus in the ophthalmic (V1) division of the trigeminal ganglion, producing a dermatomal vesicular rash that can involve the cornea, uvea, and optic nerve. Diagnosis is clinical, and first-line treatment is oral valacyclovir or famciclovir started within 72 hours of rash onset, with intravenous acyclovir for severe or immunocompromised disease.