Corneal infections (keratitis)

If you have a painful red eye, increasing light sensitivity, blurred vision, or think you may have an eye infection, this page will help you understand what infectious keratitis is, why it can become serious quickly, how it is diagnosed, and what treatment options may be needed.

Infectious keratitis is an infection of the cornea and is considered a vision-threatening eye emergency.

What it is

What is infections keratitis, and why it affects vision.

Symptoms

Common symptoms and how they often begin.

Why it happens?

Possible causes, risks, factors, behaviours.

Diagnosis

How doctors confirm the diagnosis.

Treatment paths

What treatment options are available?

Outcomes

What results can you expect after treatment.

Overview

What is a corneal infection?

Infectious keratitis occurs when microorganisms – such as bacteria, fungi, or viruses – invade the corneal tissue. The condition typically results in inflammation, ulceration (a loss of corneal tissue), and disruption of the eye’s natural protective barriers.

The risk is higher in people who wear contact lenses, have had prior eye surgery, have suffered trauma to the eye, or have pre-existing surface diseases that compromise the tear film or corneal epithelium.

An early stage of corneal infection

Symptoms

Common symptoms of corneal infection

Symptoms can escalate quickly. A corneal infection is not something to “watch for a few days.”

Blurred or distorted vision

Vision may become less sharp because the infection affects the normally clear cornea.

Light sensitivity

Many patients develop marked sensitivity to light.

Redness

The eye often becomes red and inflamed, sometimes very suddenly.

White spot on the cornea

In some cases, a pale or white spot can be seen on the clear surface of the eye.

Eye pain

Pain is one of the most important warning signs. Infectious keratitis is often much more painful than ordinary irritation or dryness.

Watering, discharge, or the feeling that something is in the eye

Patients often describe a foreign-body sensation, tearing, or discharge, especially as the surface becomes more inflamed.

Causes

Why does corneal infection happen?

A healthy cornea has natural protective barriers. Infection becomes more likely when those barriers are disrupted. Contact lens wear is one of the most common risk factors, especially if lenses are overworn, cleaned improperly, or exposed to water. Trauma, scratches, previous eye surgery, and pre-existing ocular surface disease can also make infection more likely.

Doctor's Advice

If you wear contact lenses and develop pain, redness, or blurred vision, remove the lens and seek urgent ophthalmic care.

The organism involved also depends on circumstances. Bacterial infections are common, particularly in contact lens wearers. Fungal keratitis is more often associated with trauma involving plant or organic material. Acanthamoeba keratitis is strongly associated with contact lens exposure to contaminated water. Viral keratitis, especially herpes simplex virus, follows a different pattern and may recur over time.

Types of Pathogens That Can Cause Keratitis

Infectious keratitis can be caused by several different types of microorganisms:

  • Bacterial keratitis is one of the most common forms, particularly in contact lens wearers. It can be caused by organisms such as Pseudomonas aeruginosaStaphylococcus aureus, and Streptococcus pneumoniae. These infections can progress rapidly and require immediate treatment.
  • Viral keratitis, most commonly due to herpes simplex virus (HSV), can cause recurrent infections that damage the corneal surface and nerves. Herpes zoster virus (the cause of shingles) can also involve the cornea in more severe cases.
  • Fungal keratitis tends to occur after trauma with organic material (e.g., plant matter) or in hot, humid climates. Common fungi include Fusarium and Aspergillus. These infections are often more difficult to diagnose and slower to respond to treatment.
  • Acanthamoeba keratitis is caused by a microscopic parasite, most often seen in contact lens users exposed to contaminated water. It is notoriously painful and difficult to treat.

Each type of pathogen may require a different treatment approach, and often, the exact cause isn’t immediately clear. This makes laboratory testing and clinical judgment critical in managing the condition.

Diagnosis

How is corneal infection diagnosed?

Diagnosis starts with urgent specialist examination. The doctor looks at the cornea with a slit lamp, assesses how deep and extensive the infection appears, asks about contact lenses, trauma, surgery, water exposure, and current symptoms, and determines how urgently treatment needs to begin. Because corneal ulcer management should not wait for culture results, treatment is often started immediately when infection is suspected. 

Eye history and symptoms

The doctor asks about pain, redness, blurred vision, contact lens use, trauma, recent surgery, and surface disease.

Slit lamp
Slit Lamp Examination

This helps assess the size, location, depth, and appearance of the corneal ulcer or infiltrate.

Corneal sampling in selected cases

For some ulcers, especially more severe or atypical ones, the doctor may take a sample from the cornea for microscopy, culture, or other laboratory testing to identify the organism.

Treatment

What are the treatment options for corneal infection?

Treatment depends on the cause, severity, and speed of progression. In many cases, treatment begins immediately and may require very frequent medicated drops, sometimes even around the clock at first.

Antimicrobial eye drops

These are the mainstay of treatment for many infections. The exact drops depend on whether the suspected cause is bacterial, fungal, viral, or parasitic.

Pain control and surface support

Lubrication, protective measures, and careful follow-up may be needed to support healing and protect the cornea. This is a reasonable inference from hospital patient guidance and the structure of treatment pathways.

Surgery or emergency corneal procedures in advanced cases

If there is severe thinning, perforation risk, or uncontrolled infection, additional procedures may be required to save the eye or preserve structure.

Adjunctive Therapy: PACK-CXL

In selected cases where standard antimicrobial therapy is insufficient, PACK-CXL (Photoactivated Chromophore for Keratitis – Corneal Cross-Linking) may be used as an adjunctive treatment.

PACK-CXL involves applying riboflavin (vitamin B2) to the infected cornea and then activating it with UV-A light. This produces reactive oxygen species that can damage pathogens directly and increase the cornea’s resistance to enzymatic breakdown. While it does not replace antimicrobial eye drops, it may help control infections and stabilize the cornea when used as part of a broader treatment strategy.

Bacterial Corneal Ulcer

Why Infectious Keratitis Can Be Difficult to Treat

Treating infectious keratitis is complex for several reasons:

  • Delayed diagnosis is common, especially in early stages when symptoms may resemble non-infectious irritation.
  • Resistant organisms are becoming more frequent, especially in bacterial and fungal infections.
  • Slow response to therapy is typical for fungal and Acanthamoeba infections, which may require weeks or months of treatment.
  • Corneal melting, a condition where the infection triggers enzymatic breakdown of the cornea, can lead to rapid deterioration even under treatment.

Because the infection often compromises the structural integrity of the cornea, additional interventions may be required to support healing and prevent complications.

Outcomes

What outcomes can patients expect?

Outcomes depend on how quickly treatment begins, what organism is responsible, how deep the infection is, whether the visual axis is involved, and whether the cornea develops scarring or thinning. Even with proper treatment, some infections leave a scar, and severe cases can permanently affect vision. 

That said, urgent diagnosis and well-targeted treatment can make a major difference. For many patients, the main goals are to eliminate the infection, preserve the structure of the cornea, reduce the chance of scarring, and protect long-term vision as much as possible. This is an inference based on the treatment goals consistently described across patient and clinical guidance. 

Corneal infection treatment outcomes

Why us?

Why ELZA for corneal infection care?

At ELZA Instutute, we know that infectious keratitis is both urgent and complex. Treating it well means more than confirming that an infection is present. We assess how aggressive it is, which organism may be responsible, how quickly the cornea is changing, and whether standard antimicrobial therapy is likely to be enough.

Our advantage is that we combine specialist corneal expertise with advanced treatment options. We offer PACK-CXL for selected cases as an adjunctive therapy when standard treatment alone may not be sufficient.

ELZA has contributed significantly to the scientific understanding and clinical development of PACK-CXL. We also provide dedicated access for patients from abroad through our international-patient pathway and online consultations.

For our patients, that means care in a center that is used to managing difficult corneal disease, can act quickly, and can offer both established and advanced options to help preserve vision and support corneal healing.

FAQs

Frequently asked questions

Is a corneal infection an emergency?

Yes. Corneal ulcers and infectious keratitis are considered vision-threatening conditions that require urgent treatment.

They can increase the risk substantially, especially if hygiene is poor, lenses are overworn, or they come into contact with water. 

Can a corneal infection leave a scar?

Yes. Even when the infection is treated correctly, corneal scarring can remain and may affect vision depending on location and severity.

Not always. Some infections are viral, fungal, or parasitic, and even bacterial infections may require culture-guided changes if the first treatment is not enough.

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