```html

Keratitis (Infectious)

What is Keratitis (Infectious)?

Keratitis is an inflammation of the cornea, the clear front window of the eye. When the inflammation is caused by a microorganism—bacteria, viruses, fungi, or parasites—it is called infectious keratitis. The infection can damage corneal cells, leading to pain, blurred vision, and, if untreated, permanent scarring or vision loss.

In the United States, infectious keratitis accounts for about 2 % of all emergency eye‑clinic visits, and it is one of the leading causes of corneal blindness worldwide, especially in developing regions where contact lens hygiene may be poor or trauma is common (World Health Organization, 2022).

Common Causes

Infectious keratitis is not a single disease; it is a clinical syndrome that can arise from many different pathogens. The most frequent culprits are:

• Bacterial keratitis – usually Staphylococcus aureus, Pseudomonas aeruginosa, or Streptococcus pneumoniae. Common after contact‑lens wear or ocular trauma.
• Viral keratitis – most often due to herpes simplex virus (HSV) type 1; can also be caused by varicella‑zoster virus (VZV).
• Fungal keratitis – typically Fusarium or Aspergillus species; linked to plant trauma or contaminated water.
• Acanthamoeba keratitis – a rare but serious protozoal infection, strongly associated with poor contact‑lens hygiene.
• Trauma‑related infection – a scratch or foreign body that introduces bacteria or fungi from the environment.
• Contact‑lens wear – especially extended‑wear or overnight wear lenses; the most important modifiable risk factor.
• Eye surgery complications – post‑operative infections after LASIK, cataract extraction, or corneal grafts.
• Dry‑eye or ocular surface disease – reduces the protective tear film, allowing microbes to adhere and invade.
• Immunosuppression – patients on systemic steroids, chemotherapy, or with HIV have higher susceptibility.
• Exposure to contaminated water – swimming pools, hot tubs, or freshwater sources can harbor Pseudomonas and Acanthamoeba.

Associated Symptoms

Symptoms can develop quickly (within hours) for bacterial infections or more slowly (days‑weeks) for fungal or Acanthamoeba keratitis. Typical features include:

• Redness of the eye (hyperemia)
• Severe eye pain or a gritty, foreign‑body sensation
• Blurred or decreased vision
• Photophobia (sensitivity to light)
• Watery or purulent discharge
• Tearing
• Swelling of the eyelids
• White or gray infiltrates on the cornea seen on slit‑lamp exam
• Ring‑shaped ulcer (especially in Acanthamoeba infection)

When to See a Doctor

Because infectious keratitis can progress rapidly and threaten vision, you should seek professional care promptly if you notice:

• Any new or worsening eye pain, especially if it is sharp or throbbing.
• Redness that does not improve within 24 hours.
• Blurred vision or a noticeable drop in visual acuity.
• Significant discharge (yellow, green, or pus‑like).
• History of recent eye trauma, surgery, or contact‑lens wear.
• Persistent photophobia or a feeling that light is intolerable.
• Any white or gray spot on the cornea that you can see with a flashlight.

Diagnosis

Eye specialists (ophthalmologists or optometrists with cornea expertise) use a combination of history, visual‑acuity testing, and specialized examinations:

1. Slit‑lamp biomicroscopy – a high‑magnification microscope that reveals corneal infiltrates, ulcer size, depth, and the presence of hypopyon (pus in the anterior chamber).
2. Fluorescein staining – a dye that highlights epithelial defects; the pattern helps differentiate bacterial from viral or fungal ulcers.
3. Corneal scraping – a tiny sample taken from the ulcer edge for Gram stain, culture, and confocal microscopy. This is the gold standard for identifying the pathogen.
4. Polymerase chain reaction (PCR) – increasingly used for rapid detection of viral DNA (e.g., HSV) or Acanthamoeba.
5. Imaging – Anterior‑segment optical coherence tomography (AS‑OCT) can assess ulcer depth and stromal involvement.

Laboratory results guide targeted therapy, but treatment often begins empirically (before culture results) to prevent progression.

Treatment Options

Management is aimed at eradicating the pathogen, reducing inflammation, and preserving corneal integrity.

Medical Treatments

• Topical antibiotics – First‑line for bacterial keratitis. Common regimens include fortified cefazolin (50 mg/mL) plus tobramycin (14 mg/mL) or fluoroquinolone drops (e.g., moxifloxacin 0.5 %). Dosing is intensive (every 1‑2 hours) initially.
• Topical antivirals – For HSV keratitis, 5 % topical acyclovir ointment or 0.15 % ganciclovir gel is used, often combined with oral antivirals (e.g., acyclovir 400 mg five times daily) for dendritic lesions.
• Topical antifungals – Natamycin 5 % suspension is the drug of choice for filamentous fungi; voriconazole 1 % drops may be used for resistant cases.
• Topical anti‑Acanthamoeba agents – A combination of polyhexamethylene biguanide (PHMB 0.02 %) or chlorhexidine 0.02 % with propamidine isethionate (Brolene) is standard. Treatment may last weeks to months.
• Corticosteroids – Used cautiously after the infection is controlled (usually 48–72 h) to reduce stromal inflammation and scarring, especially in bacterial and HSV keratitis. Not indicated in fungal or Acanthamoeba infections.
• Pain control – Oral NSAIDs, cycloplegic drops (e.g., cyclopentolate) to relieve ciliary spasm, and, in severe pain, short‑acting opioids under medical supervision.

Adjunctive & Surgical Therapies

• Therapeutic contact lens – Bandage lenses protect the cornea, promote epithelial healing, and improve drug delivery.
• Corneal debridement – Mechanical removal of necrotic tissue can enhance penetration of topical medication.
• Amniotic membrane transplantation – Provides a biologic scaffold and anti‑inflammatory factors for deep or non‑healing ulcers.
• Penetrating keratoplasty (corneal transplant) – Reserved for perforation or scarring that threatens vision.

Home Care & Self‑Management

• Apply prescribed eye drops exactly as directed; missing doses can allow the organism to rebound.
• Avoid rubbing the eye—a risk for additional trauma and spread of infection.
• Use a clean, preservative‑free artificial tear regimen if recommended to keep the ocular surface moist.
• Do not wear contact lenses until the eye is completely cleared and your doctor gives written clearance.
• Maintain a balanced diet rich in vitamins A, C, and omega‑3 fatty acids, which support ocular surface health.

Prevention Tips

Many cases of infectious keratitis are preventable with simple hygiene measures and awareness:

• Hand hygiene – Wash hands with soap and water before touching eyes or handling lenses.
• Contact‑lens care –
  • Never sleep in lenses unless they are explicitly labeled for overnight wear.
  • Replace lenses and storage cases according to the manufacturer’s schedule (often every 2‑4 weeks).
  • Use only the recommended disinfecting solution; never top‑up old solution.
  • Avoid water exposure (swimming, showering) while lenses are in place.
• Protective eyewear – Wear goggles during high‑risk activities (gardening, woodworking, sports) to prevent corneal abrasions.
• Prompt treatment of ocular trauma – Clean any scratches with sterile saline and seek care if the wound is >2 mm or if a foreign body remains.
• Regular eye examinations – Especially for contact‑lens wearers, diabetics, or individuals with chronic dry‑eye disease.
• Avoid sharing eye cosmetics or drops – Bacterial contamination spreads easily.
• Stay up‑to‑date on vaccinations – For example, varicella vaccination reduces the risk of VZV keratitis later in life.

Emergency Warning Signs

Key Take‑aways

• Infectious keratitis is an urgent eye condition that can lead to permanent vision loss if not treated promptly.
• Bacterial, viral, fungal, and protozoal pathogens each require different topical or systemic medications; early empiric therapy saves sight.
• Contact‑lens hygiene, eye‑protective gear, and prompt attention to eye injuries are the most effective preventive measures.
• Red‑flag symptoms—rapid vision loss, severe pain, white corneal infiltrates, or systemic illness—warrant immediate emergency evaluation.

For the most current guidelines, see the American Academy of Ophthalmology (AAO) Preferred Practice Pattern for Infectious Keratitis (2023) and the CDC recommendations for contact‑lens safety (2022). If you suspect keratitis, do not delay—early professional care dramatically improves outcomes.

```