Keratitis (Karititis)

"Karititis" appears to be an alternate spelling or phonetic transcription of keratitis - inflammation of the cornea, the clear dome-shaped tissue covering the front of the eye.

Definition

Keratitis is inflammation of the corneal stroma, epithelium, or both. It may be infectious (bacterial, viral, fungal, protozoal) or non-infectious (trauma, exposure, autoimmune, toxic).

Types and Causes

1. Bacterial Keratitis

The most common form in contact lens wearers. Key pathogens:

Pseudomonas aeruginosa - Gram-negative rod; ubiquitous in the environment; responsible for >60% of contact lens-related keratitis. Typically aggressive.
Staphylococcus aureus - Gram-positive commensal of skin/nares; presents as a focal, fairly well-defined white/yellow-white infiltrate.
Streptococci (S. pneumoniae, S. pyogenes) - often aggressive course.
Special organisms like Neisseria gonorrhoeae and Corynebacterium diphtheriae can penetrate an intact corneal epithelium - this is unusual.

Risk factors:

Contact lens wear (especially extended-wear soft lenses) - the single most important risk factor
Corneal trauma, including refractive surgery (LASIK)
Chronic ocular surface disease
Systemic immunosuppression

2. Viral Keratitis (Herpetic / HSV Keratitis)

The classic form is epithelial (dendritic) keratitis - caused by active HSV replication.

Clinical features (in chronological order):

Reduced visual acuity
Swollen opaque epithelial cells in a coarse punctate or stellate pattern
Central desquamation producing a linear-branching (dendritic) ulcer - the hallmark finding
Branches have characteristic terminal buds; bed stains with fluorescein
Virus-laden cells at the margin stain with rose Bengal
Corneal sensation is reduced
Mild subepithelial haze
Anterior chamber activity usually mild

Important warning: Topical steroids can promote progressive enlargement of the ulcer to a "geographic" or "amoeboid" configuration.

Classic fluorescein image of herpetic dendritic keratitis:

Dendritic (branching) ulcer of herpetic keratitis under fluorescein staining

Fluorescein staining showing the characteristic branching (dendritic) pattern of HSV epithelial keratitis - Kanski's Clinical Ophthalmology, 10th ed.

3. Fungal Keratitis

Rare in temperate climates but a major cause of visual loss in tropical/low-income regions.

Yeasts (Candida): most common in temperate climates; yellow-white densely suppurative infiltrate
Filamentous fungi (Fusarium, Aspergillus): dominant in tropical climates; associated with plant/agricultural trauma
- Grey or yellow-white stromal infiltrate with indistinct fluffy margins
- Satellite lesions; feathery branch-like extensions
- Can penetrate an intact Descemet membrane and cause endophthalmitis without perforation

Predisposing factors: Long-term topical steroids, chronic ocular surface disease, contact lens wear, systemic immunosuppression, diabetes.

4. Acanthamoeba Keratitis

Associated with contact lens wear and exposure to contaminated water (tap water, swimming pools)
Potentially devastating; often initially culture-negative for bacteria
Increasing in frequency
Pain classically out of proportion to clinical signs

Clinical Features (General)

Feature	Details
Symptoms	Eye pain, redness, photophobia, blurred vision, watering/discharge
Signs	Corneal infiltrate, epithelial defect, anterior uveitis, hypopyon (in severe cases)
Severe complications	Descemetocoele, corneal perforation, endophthalmitis, vision loss

In moderate-severe bacterial keratitis: stromal oedema, Descemet folds, anterior uveitis with hypopyon, chemosis, eyelid swelling. Severe Pseudomonas infections can perforate rapidly.

Investigations

Corneal scraping - recommended for ulcers that are: >2 mm, involve mid-to-deep stroma, are within the visual axis, chronic, or atypical in appearance
Gram stain, bacterial/fungal cultures, viral PCR
Use non-preserved topical anaesthetic (preservatives lower bacterial viability)
Scrape from the margins and base of the ulcer

Management Principles

Infectious Keratitis

Topical fluoroquinolones (e.g., ciprofloxacin) are first-line for bacterial keratitis - active against most common pathogens, though resistance exists
Culture before starting antibiotics when possible
For viral (HSV): topical antivirals (e.g., aciclovir, ganciclovir); avoid steroids in epithelial disease
For fungal: topical antifungals (natamycin for filamentous, amphotericin B for Candida)
Urgent ophthalmology referral - always; if not possible, phone guidance within 24 hours

Caution with Steroids

Topical corticosteroids can promote HSV and fungal replication and retard re-epithelialization. They must be used carefully and only under specialist supervision.

Promoting Epithelial Healing

Artificial tears, antibiotic ointment prophylaxis
Bandage soft contact lenses (with close supervision)
Corneal cross-linking with UV-A + riboflavin (PACK-CXL) for resistant infections with corneal melting
Amniotic membrane grafting for persistent epithelial defects
Tissue cyanoacrylate glue for small perforations
Tarsorrhaphy for exposure or neurotrophic cases

Key Differentials

Marginal keratitis (peripheral; often immune-mediated)
Sterile inflammatory infiltrates from contact lens wear
Peripheral ulcerative keratitis (autoimmune)
Toxic keratitis
Conjunctivitis / keratoconjunctivitis

Bottom line: Keratitis is an ophthalmologic emergency. Early slit-lamp examination, culture where indicated, and prompt antimicrobial therapy are the cornerstones of management. Any patient with eye pain, redness, and reduced vision should be seen by an ophthalmologist urgently to prevent permanent vision loss.

Sources: Kanski's Clinical Ophthalmology, 10th ed.; Roberts and Hedges' Clinical Procedures in Emergency Medicine; Goldman-Cecil Medicine

This is a shared conversation. Sign in to Orris to start your own chat.