Infective Keratitis

Infective keratitis is corneal inflammation due to microbial infection. It is a true ophthalmic emergency: delayed treatment can lead to corneal scarring, perforation, and permanent blindness. Contact lens wear, trauma, and ocular surface disease are major risk factors.

🔎 Etiology

• Bacterial: Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa (esp. in contact lens wearers).
• Viral: Herpes simplex virus (HSV), Varicella zoster virus (VZV).
• Fungal: Fusarium, Aspergillus, Candida (more common in agricultural trauma, immunosuppression).
• Protozoal: Acanthamoeba keratitis (linked with poor contact lens hygiene, swimming in lenses).

📋 Clinical Features

• Severe ocular pain, redness, photophobia, tearing.
• Decreased or blurred vision.
• Corneal ulcer/infiltrate visible with fluorescein staining.
• Hypopyon (layer of pus in anterior chamber) in severe bacterial/fungal keratitis.
• Ring infiltrate in Acanthamoeba.
• Dendritic ulcers with fluorescein uptake in HSV keratitis.

📊 Infective Keratitis – Key Differentials

🧪 Investigations

• Slit-lamp examination: Defines size, depth, and location of corneal lesion.
• Fluorescein staining: Highlights epithelial defects.
• Corneal scrape for Gram stain/culture: Guides antimicrobial therapy.
• PCR/viral swabs: For HSV/VZV when suspected.
• Contact lens case and solution culture if relevant.

💊 Management

• Urgent ophthalmology referral – do not delay.
• Bacterial: Intensive broad-spectrum topical antibiotics (e.g. fortified ceftazidime + vancomycin, or fluoroquinolone drops hourly).
• Viral (HSV): Topical aciclovir 3% ointment or ganciclovir gel; avoid topical steroids unless under specialist supervision.
• Fungal: Topical natamycin or voriconazole drops ± systemic antifungal in severe cases.
• Acanthamoeba: Biguanides (PHMB or chlorhexidine) + diamidines; prolonged therapy required.
• Protective eye shield; avoid contact lenses until complete healing.

⚠️ Complications

• Corneal scarring → visual impairment.
• Corneal perforation → endophthalmitis.
• Secondary glaucoma.
• Blindness or need for corneal transplant.

📝 Exam Pearls

• Contact lens wearer + painful red eye + corneal ulcer → Pseudomonas keratitis until proven otherwise.
• Branching dendritic ulcer on fluorescein → classic for HSV keratitis.
• Always culture before antibiotics if possible, but never delay treatment for severe cases.
• Do not give topical steroids in suspected HSV keratitis unless under specialist advice.

👁️ Case 1 — Bacterial Keratitis (Contact Lens-Associated)

A 26-year-old woman who wears soft contact lenses overnight presents with a painful red eye, photophobia, and reduced vision. Examination reveals a corneal ulcer with surrounding infiltrate. 💡 Bacterial keratitis is often due to Pseudomonas aeruginosa in contact lens users. It is an ophthalmic emergency, as rapid progression can lead to corneal perforation. Management includes immediate corneal scrape for culture and intensive topical fluoroquinolone antibiotics, with urgent ophthalmology involvement.

👁️ Case 2 — Fungal Keratitis

A 45-year-old agricultural worker presents with a red, painful eye and blurred vision following minor trauma with a tree branch. Slit-lamp exam shows a feathery corneal infiltrate with satellite lesions. 💡 Fungal keratitis, commonly due to Fusarium or Aspergillus, often follows trauma with plant material in tropical or rural settings. It progresses insidiously but is difficult to treat. Management involves corneal scraping, topical antifungals (natamycin or voriconazole), and close monitoring, with keratoplasty considered if severe.

👁️ Case 3 — Viral Keratitis (Herpes Simplex)

A 32-year-old man presents with recurrent episodes of a painful, watery red eye with blurred vision. Slit-lamp examination and fluorescein staining reveal a branching dendritic ulcer of the cornea. 💡 Herpes simplex keratitis is the most common cause of corneal blindness in developed countries. It results from reactivation of latent HSV in the trigeminal ganglion. M