12.3 Infectious Keratitis, Infiltrative Events & Acute Triage Protocols

12.3 Microbial Keratitis, Infiltrative Events & Acute Triage

A painful red eye in a contact-lens wearer must be treated as potentially infectious until an appropriately licensed clinician evaluates it. Delay can cost vision, while premature reassurance or steroid use can worsen infection.

Recognize High-Risk Features

Urgent features include:

• moderate or severe pain, photophobia, or reduced vision;
• focal epithelial defect over or near a stromal infiltrate;
• rapid progression, stromal thinning, suppuration, or purulent discharge;
• anterior-chamber cells, flare, fibrin, or hypopyon;
• recent overnight wear, water exposure, trauma, poor hygiene, or immunosuppression;
• a graft, neurotrophic cornea, or recent surgery;
• symptoms that persist or worsen after lens removal.

The size, location, and relationship between epithelial defect and infiltrate help risk assessment, but no single ratio proves infection or sterility. Small peripheral events can be infectious, and sterile inflammatory events can have epithelial loss.

Sterile Infiltrative Events

Contact Lens Peripheral Ulcer and Contact Lens Acute Red Eye are inflammatory syndromes often associated with bacterial toxins, hypoxia, or overnight wear. They may be smaller, more peripheral, less painful, and accompanied by a quieter anterior chamber than microbial keratitis. These patterns are useful, but overlap exists. When doubt remains, urgent medical evaluation is the correct exam choice.

Important Organisms

Pseudomonas aeruginosa can progress rapidly and cause stromal necrosis. Acanthamoeba is associated with tap water, swimming, hot tubs, homemade saline, and contaminated cases. Early Acanthamoeba disease may produce severe pain out of proportion to visible signs, pseudodendrites, or radial perineural infiltrates. Radial keratoneuritis is highly suggestive but not pathognomonic; it can occur in other infections and is absent in many Acanthamoeba cases.

Fungal keratitis should be considered after vegetative trauma or in relevant environments. Clinical appearance suggests possibilities but laboratory testing and medical judgment establish treatment.

Immediate Triage

For a suspected microbial keratitis:

1. instruct the patient to stop contact-lens wear immediately;
2. arrange same-day urgent evaluation by an optometrist or ophthalmologist authorized to diagnose and treat, with corneal-specialist or emergency referral when indicated;
3. do not patch the eye;
4. do not advise leftover antibiotic, anesthetic, or steroid use;
5. ask the patient to bring the lenses, case, and solutions; retain them for culture only as directed and without contaminating them;
6. document onset, symptoms, visual acuity if within scope, lens type, wear schedule, water exposure, solutions, and referral communication;
7. give explicit escalation instructions if the patient cannot reach the receiving clinician.

Corneal scraping, culture, antimicrobial selection, cycloplegia, and steroid timing are medical decisions. A technician should not delay referral in order to perform tests outside scope.

Why Steroids and Patching Are Unsafe Before Evaluation

A patch creates a warm closed environment and prevents monitoring. Topical corticosteroids can suppress host response and worsen untreated bacterial, fungal, or Acanthamoeba infection. Steroids may have a role later in selected infections under specialist supervision, but they are not a first-aid treatment for an undiagnosed contact-lens red eye.

Emergency Communication

A useful referral message includes:

• affected eye and symptom onset;
• pain, photophobia, discharge, and change in acuity;
• infiltrate and epithelial-defect location and approximate size;
• anterior-chamber reaction or corneal thinning if observed;
• lens type, overnight wear, trauma, and water exposure;
• all drops already used;
• whether the lens and case are available.

Confirm that the receiving office accepted the patient and document the time. “Return if worse” without arranging evaluation is not adequate when microbial keratitis is suspected.

Prevention Review After Resolution

Once the treating clinician permits lens wear, review hand hygiene, replacement, labeled disinfection, case care, no-water behavior, and overnight-wear restrictions. Inspect the fit and ocular surface and coordinate any redesign. Prevention counseling does not replace treatment of the acute episode.

Comparison

The table guides suspicion, not a definitive diagnosis.

Exam Traps

• “Peripheral” does not mean sterile.
• Radial keratoneuritis suggests Acanthamoeba but is not pathognomonic.
• Do not patch or start steroids before infectious evaluation.
• Retaining a lens and case is useful only if handled for possible culture as directed.
• Same-day referral is the priority when infection cannot be excluded.