Bacterial Keratitis

Bacterial keratitis occurs when the corneal epithelium is compromised, allowing bacteria to enter the stroma. The most common causative organisms include Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae. Research published in The Lancet Infectious Diseases (2023) suggests that the rise of antibiotic-resistant strains, such as Methicillin-resistant Staphylococcus aureus (MRSA), is complicating the etiology of these infections.

Non-Modifiable Risk Factors

• Prior Ocular Surgery: Procedures like LASIK or cataract surgery can create pathways for infection.
• Chronic Ocular Surface Disease: Conditions like Stevens-Johnson syndrome or ocular cicatricial pemphigoid weaken the eye's natural defenses.
• Systemic Immunosuppression: Diabetes or HIV can impair the body's ability to fight off ocular pathogens.

Modifiable Risk Factors

• Contact Lens Wear: This is the leading risk factor in developed nations. Poor hygiene, sleeping in lenses, or using tap water for cleaning increases risk exponentially.
• Ocular Trauma: Scratches from fingernails, tree branches, or metallic foreign bodies introduce bacteria directly into the tissue.
• Contaminated Eye Medications: Using expired drops or touching the tip of a bottle to an infected surface.

According to the American Academy of Ophthalmology (AAO, 2024), contact lens wearers are 10 to 15 times more likely to develop ulcerative keratitis than non-wearers. Individuals working in agriculture or construction are also at higher risk due to the increased frequency of corneal abrasions and exposure to environmental pathogens.

Prevention is centered on maintaining the integrity of the corneal barrier. Evidence-based strategies include:

• Strict Contact Lens Hygiene: Following the "rub and rinse" method and replacing cases every three months.
• Protective Eyewear: Using safety goggles during high-risk activities (e.g., mowing, grinding metal).
• Managing Dry Eye: Keeping the ocular surface lubricated to prevent micro-tears in the epithelium.

The diagnostic journey begins with an urgent ophthalmic evaluation. Because bacterial keratitis can progress to permanent blindness within hours, clinicians prioritize rapid identification of the pathogen and the extent of the damage.

Your healthcare provider will perform a visual acuity test followed by a slit-lamp examination. This specialized microscope allows the doctor to see the cornea in high magnification. They will look for the presence of a corneal infiltrate (a collection of inflammatory cells) and assess the depth of any ulceration.

• Fluorescein Staining: A yellow dye is placed in the eye. Under a blue light, the dye highlights areas where the corneal epithelium is missing, revealing the size and shape of an ulcer.
• Corneal Scraping and Culture: This is the gold standard for diagnosis. The doctor gently scrapes the surface of the ulcer to collect a sample. This sample is sent to a lab to identify the specific bacteria and determine which antibiotics will be most effective (sensitivity testing).
• In Vivo Confocal Microscopy: In complex cases, this non-invasive imaging can provide high-resolution images of the corneal layers to rule out fungal or parasitic infections.

Diagnosis is primarily clinical, based on the presence of a corneal epithelial defect with an underlying stromal infiltrate. The American Academy of Ophthalmology (2024) guidelines suggest that any central or large ulcer must be cultured to guide therapy.

Several conditions can mimic bacterial keratitis, including:

• Fungal Keratitis: Often follows trauma with vegetable matter (e.g., a branch).
• Acanthamoeba Keratitis: A rare but severe infection often related to contaminated water and contact lenses.
• Herpes Simplex Keratitis: Usually presents with a characteristic "dendritic" (tree-like) pattern on the cornea.
• Sterile Infiltrates: Inflammatory reactions to contact lens overwear that are not actually infected.

The primary goals of treatment are to eliminate the causative bacteria, reduce inflammation to minimize scarring, and promote the re-epithelialization of the corneal surface.

According to the AAO Preferred Practice Pattern (2024), the standard initial approach involves the frequent application of topical antimicrobial drops. In many cases, "loading doses" are administered every 15 to 30 minutes for the first several hours, followed by hourly applications around the clock.

• Fluoroquinolone Antibiotics: These are often the first choice due to their broad-spectrum activity and excellent corneal penetration. They work by inhibiting bacterial DNA synthesis.
• Aminoglycoside Antibiotics: Often used in combination with other drops for severe infections, particularly those suspected to be caused by Gram-negative bacteria like Pseudomonas.
• Cephalosporin Antibiotics: In severe or resistant cases, pharmacists may prepare "fortified" versions of these drugs at much higher concentrations than standard commercial drops.
• Cycloplegics: These drops dilate the pupil and paralyze the ciliary muscle. While they don't treat the infection, they significantly reduce pain by stopping internal eye spasms.

If the infection does not respond to initial treatment, healthcare providers may adjust therapy based on culture results. Topical corticosteroids may be introduced only after the infection is under control to reduce scarring, though their use remains a subject of clinical debate.

• Corneal Collagen Cross-Linking (CXL): Emerging research suggests that CXL, which uses UV light and riboflavin to strengthen the cornea, may also help kill bacteria and stop corneal "melting."
• Tectonic Keratoplasty: In cases of imminent perforation, an emergency corneal transplant may be required to save the structural integrity of the eye.

Patients are typically monitored daily until the infection shows clear signs of stabilization. Treatment often lasts several weeks, with a slow tapering of drops to prevent recurrence.

> Important: Talk to your healthcare provider about which approach is right for you.

While diet does not cure an active infection, supporting the immune system is vital for healing. Research published in the British Journal of Ophthalmology suggests that Vitamin A deficiency can compromise corneal integrity. A diet rich in leafy greens, carrots, and omega-3 fatty acids may support overall ocular surface health.

During an active infection, vigorous exercise should be avoided. Increased blood pressure and sweating can irritate the eye. Furthermore, the risk of accidental trauma to the weakened cornea is high. Patients should avoid swimming in pools, lakes, or hot tubs until the doctor confirms the corneal surface has fully healed.

Rest is critical, but the treatment schedule for bacterial keratitis often requires waking up every hour for eye drops. To manage this, patients may need assistance from family members to ensure no doses are missed. Using a cool-mist humidifier in the bedroom may help prevent the eye from drying out during the short intervals of sleep.

The threat of vision loss is highly stressful. Evidence-based techniques such as mindful breathing or guided imagery can help patients manage the anxiety associated with frequent clinical procedures and the pain of the infection.

There is no evidence that herbal remedies or supplements can treat bacterial keratitis. Some patients find relief using cool (not cold) compresses over the closed eyelid to reduce swelling, but this should only be done with a doctor's approval to avoid contamination.

Caregivers play a vital role in the "round-the-clock" dosing schedule. It is helpful to keep a log of every drop administered. Always wash hands thoroughly before and after touching the patient's face to prevent spreading the bacteria or introducing new pathogens.

The prognosis for bacterial keratitis depends heavily on the speed of diagnosis, the location of the ulcer, and the virulence of the bacteria. According to a study in Clinical Ophthalmology (2023), over 80% of patients achieve infection resolution with prompt antibiotic therapy. However, if the ulcer is central, some degree of permanent vision loss due to scarring is common.

• Corneal Scarring: The most frequent long-term complication, which can cause irregular astigmatism or opacification.
• Glaucoma: Secondary inflammation can block fluid drainage in the eye, leading to high intraocular pressure.
• Endophthalmitis: A catastrophic complication where the infection spreads to the interior of the eyeball.
• Corneal Perforation: The "melting" of the cornea until it develops a hole, requiring emergency surgery.

After the infection clears, patients may require specialized contact lenses (scleral lenses) to see through a scarred cornea. Regular follow-ups are necessary to monitor for recurrence or chronic dry eye.

If vision is permanently affected, low-vision rehabilitation can help patients adapt. Most importantly, survivors of bacterial keratitis must be extremely vigilant about future eye health, often choosing to cease contact lens wear entirely to prevent a second occurrence.

Contact your ophthalmologist immediately if you notice a return of redness, a sudden change in vision, or if the eye begins to feel increasingly painful after initial improvement.