Ophthalmology · Infectious Keratitis
The facts most likely to be tested
Contact lens wear is the most significant risk factor for Pseudomonas aeruginosa-associated corneal ulcers.
Fluorescein staining reveals a corneal epithelial defect that pools dye, confirming the diagnosis of a corneal ulcer.
Herpes simplex keratitis presents with a pathognomonic dendritic ulcer visible under slit-lamp examination with fluorescein.
Bacterial keratitis typically presents with a white, hazy infiltrate and associated purulent discharge.
Fungal keratitis is strongly associated with vegetative trauma and presents with feathery, irregular borders on the cornea.
Acanthamoeba keratitis should be suspected in contact lens wearers who report severe, disproportionate pain and have a history of swimming or using tap water to clean lenses.
Topical corticosteroids are strictly contraindicated in the initial management of suspected infectious corneal ulcers as they can worsen the infection and lead to corneal perforation.
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A 24-year-old graduate student presents to the urgent care clinic complaining of severe left eye pain, photophobia, and blurred vision for the past 2 days. She admits to wearing her soft contact lenses overnight for the past week. On physical examination, there is conjunctival injection and a white, opaque infiltrate noted on the central cornea. Fluorescein staining demonstrates a focal epithelial defect with surrounding stromal edema.
What is the most likely diagnosis and the most appropriate initial management?
Bacterial corneal ulcer (infectious keratitis); discontinue contact lens use and initiate topical fluoroquinolone antibiotics.
The patient's history of contact lens use combined with the classic finding of a corneal infiltrate and epithelial defect is diagnostic for a bacterial corneal ulcer, which requires immediate cessation of contact lens wear and empiric antibiotic coverage.
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High yield triage
Etiology / Epidemiology
Primary risk factor is contact lens wear (especially overnight). Bacterial pathogens include Pseudomonas (lens wearers) and Staph aureus.
Clinical Manifestations
Presents with pain, photophobia, and decreased visual acuity. Exam shows ciliary injection and a white corneal infiltrate.
Diagnosis
Fluorescein staining reveals a corneal epithelial defect. Slit-lamp examination is the gold standard for visualization.
Treatment
Immediate topical fluoroquinolones (e.g., moxifloxacin). Do not patch the eye as this promotes bacterial growth.
Prognosis
Risk of corneal scarring and permanent vision loss. Requires urgent ophthalmology referral to prevent perforation.
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Epidemiology & Etiology
Most cases are infectious, with contact lens wear being the leading risk factor. Other causes include ocular trauma, dry eye, and exposure keratopathy. Pseudomonas aeruginosa is the most feared pathogen in lens wearers due to rapid progression.
Pertinent Anatomy
The cornea is an avascular structure, making it highly susceptible to infection once the epithelial barrier is breached. The limbus serves as the vascular border; inflammation here, known as ciliary flush, indicates deep ocular involvement.
Pathophysiology
Epithelial disruption allows microbial invasion into the corneal stroma. The host inflammatory response leads to the formation of a corneal infiltrate and subsequent tissue necrosis. If untreated, the ulcer can progress to corneal perforation and endophthalmitis.
Clinical Manifestations
Patients report severe ocular pain, foreign body sensation, and photophobia. Physical exam reveals ciliary injection (limbal redness) and a white, hazy corneal opacity. Red flags include hypopyon (pus in the anterior chamber) and significant vision loss.
Diagnosis
Fluorescein staining is the diagnostic test of choice, showing a corneal epithelial defect that pools the dye. Slit-lamp examination is required to assess the depth of the ulcer and check for an associated hypopyon.
Treatment
Initiate topical fluoroquinolones (e.g., moxifloxacin or ciprofloxacin) immediately. Never patch the eye, as this creates a warm, dark environment that accelerates bacterial replication. Patients must discontinue contact lens use and receive urgent ophthalmology follow-up.
Prognosis
Prompt treatment is essential to prevent corneal scarring and permanent visual impairment. Complications include corneal perforation and secondary glaucoma. Patients require daily monitoring until the corneal infiltrate begins to resolve.
Differential Diagnosis
Herpes Simplex Keratitis: dendritic ulcer on fluorescein staining
Corneal Abrasion: absence of a white infiltrate
Acute Angle-Closure Glaucoma: mid-dilated fixed pupil and steamy cornea
Uveitis: cells and flare in the anterior chamber
Dacryocystitis: inflammation localized to the lacrimal sac