Conditions · Ophthalmology and ENT
Keratitis and corneal ulcer !
Keratitis is inflammation or infection of the cornea; an ulcer is an open sore on it. Contact lenses are a major cause, and it can cost vision fast.
Updated 2026-11-01
Structures involved
Tap one to see what it is and open it in 3D.
Microorganisms that cause it
Why it happens
- Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer
- The eye wall: cornea, sclera, uvea and lens
What it is
Inflammation of the cornea, the clear front window of the eye, most often from infection. When the surface layer is lost and the stroma is infiltrated, it forms a corneal ulcer, an ophthalmic emergency.
Who gets it
Infectious keratitis is a leading cause of corneal blindness worldwide. In tropical regions, including Colombia, fungal keratitis after injuries with plant matter in agricultural workers is relatively common; in cities, contact-lens-related bacterial keratitis predominates.
Causes
- Bacteria: Staphylococcus, Streptococcus pneumoniae and Pseudomonas aeruginosa (typical in contact lens wearers)
- Viruses: herpes simplex (dendritic ulcer) and varicella-zoster
- Fungi: Fusarium and Aspergillus after plant trauma; Candida in diseased or immunosuppressed eyes
- Acanthamoeba: contact lenses rinsed or stored in tap water or homemade solutions, or worn while swimming
- Non-infectious: exposure (incomplete lid closure), severe dry eye, ultraviolet injury, autoimmune disease
Risk factors
- Contact lens use, especially overnight wear and poor lens hygiene (the main risk factor)
- Corneal trauma or a foreign body, particularly with vegetable matter
- Ocular surface disease: dry eye, lagophthalmos (e.g. facial palsy), eyelid malposition
- Topical corticosteroid use, diabetes and immunosuppression
- Previous herpetic eye disease or corneal surgery
Pathophysiology
A break in the corneal epithelium lets organisms attach and invade the stroma; some, such as Neisseria, can penetrate an intact surface. Bacterial and host enzymes destroy collagen, producing a white infiltrate, stromal thinning and inflammation in the anterior chamber (hypopyon). Without treatment the stroma melts and the cornea can perforate; healing leaves a scar that blurs vision.
Classification
- By cause: bacterial, viral (herpes simplex, zoster), fungal, protozoal (Acanthamoeba), non-infectious
- By depth: epithelial, stromal, endothelial
- Ulcerative vs non-ulcerative keratitis
Symptoms and signs
- Eye pain, often severe, with foreign-body sensation
- Red eye with redness concentrated around the cornea (ciliary flush)
- Photophobia and tearing or discharge
- Blurred vision
- White or grey spot on the cornea
Diagnosis
- Clinical
- Slit-lamp examination with fluorescein staining shows the epithelial defect and infiltrate; herpes simplex gives a branching dendritic pattern with reduced corneal sensation. Visual acuity is recorded.
- Tests
- Corneal scrapings for Gram and other stains and cultures (bacterial, fungal, Acanthamoeba media) for large, deep, central or atypical ulcers; PCR for herpes; culture of contact lenses and case.
- Imaging
- Usually not needed; confocal microscopy can show Acanthamoeba cysts or fungal hyphae; anterior-segment OCT measures thinning.
Differential diagnosis
- Conjunctivitis (no corneal infiltrate, little pain or photophobia)
- Corneal abrasion
- Anterior uveitis
- Acute angle-closure glaucoma
- Sterile marginal (immune) infiltrates
Goal of treatment
Eradicate the infection quickly to limit scarring and avoid perforation, then restore a clear cornea and useful vision.
Treatment
- Acute
- Stop contact lens wear and refer urgently to ophthalmology; do not patch an eye with suspected infection.
- Medical
- Intensive topical broad-spectrum antibiotics (fluoroquinolones, or fortified antibiotics for large ulcers) while cultures are pending; topical antivirals or oral antivirals for herpes; topical antifungals (natamycin, voriconazole) for fungi; biguanides for Acanthamoeba.
- Medical
- Cycloplegic drops for pain; topical corticosteroids only under specialist care once a bacterial infection is responding, and never in fungal, Acanthamoeba or epithelial herpetic disease.
- Surgical
- Corneal transplant (keratoplasty) for perforation, non-healing ulcers or dense scarring; tissue adhesive or amniotic membrane for small perforations.
- Follow-up
- Daily or frequent review of infiltrate size, epithelial defect and pain; nursing focus on drop schedules, hand hygiene and lens care education.
Complications
- Corneal scarring and irregular astigmatism
- Corneal thinning and perforation
- Endophthalmitis
- Secondary glaucoma and cataract
- Permanent vision loss or loss of the eye
Prognosis
Small peripheral bacterial ulcers usually heal with little effect on vision. Central, large or fungal and Acanthamoeba infections heal slowly and often scar, and some need a corneal transplant.
Prevention
- Hand washing and proper contact lens care; no sleeping or swimming in lenses; never tap water on lenses
- Protective eyewear in agriculture and industry
- Lubrication and lid protection in people who cannot close the eye
Test yourself
Think of the answer, then tap the question to see it.
Which organism classically causes keratitis in soft contact lens wearers?
Pseudomonas aeruginosa; Acanthamoeba is linked to lenses exposed to tap water or homemade solutions.
What corneal pattern on fluorescein suggests herpes simplex keratitis?
A branching dendritic ulcer, often with reduced corneal sensation.
Which keratitis is typical after corneal injury with plant material?
Fungal keratitis (e.g. Fusarium, Aspergillus).
Why must topical corticosteroids be avoided in undiagnosed keratitis?
They can worsen herpetic epithelial, fungal and Acanthamoeba infections and speed corneal melting.
Related conditions
- Conjunctivitis
- Corneal abrasion and ocular foreign body
- Genital herpes (herpes simplex infection)
- Herpes zoster ophthalmicus
- Endophthalmitis
- Dry eye disease
- Uveitis
- Bell palsy
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Corneal ulcers and infections: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2024); Bacterial Keratitis (EyeWiki (American Academy of Ophthalmology), 2025).
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