Keratitis: Types, Symptoms, Causes, and Treatment Explained

A red, painful eye or sudden blurring of vision can quickly turn from a minor worry into real concern. Many people initially assume these symptoms are due to simple irritation, digital eye strain, or dryness. However, in some cases, they may be early signs of keratitis, an inflammation of the cornea, the clear front window of the eye that plays a vital role in vision.

When keratitis, or a related eye infection or disease, is not assessed and correctly recognised on time, it may lead to complications that affect vision. Understanding keratitis and associated eye conditions, their symptoms, causes, and treatment options can help patients recognise when to seek timely professional care.

In this blog, you will learn about what keratitis is, different types of keratitis, common keratitis symptoms, how microbial keratitis is diagnosed and how keratitis treatment is generally approached by eye care professionals.

Please note that this content serves educational purposes only and does not replace professional medical advice. For sudden, severe or persistent eye symptoms, we recommend booking an urgent eye examination. You can schedule this with the team at AccuVision.

Experiencing Redness or Eye Pain?

Persistent discomfort, redness or sudden blurred vision should be assessed promptly. A comprehensive eye examination at AccuVision can help identify the cause and guide appropriate care.

What Is Keratitis?

Keratitis is inflammation of the cornea, the transparent front surface of the eye that helps focus light onto the retina. When the cornea becomes inflamed or infected, it can affect vision and cause discomfort or pain.

Keratitis can be:

• Infectious (e.g., microbial keratitis): keratitis caused by bacteria, fungi, viruses, or parasites.
• Non‑infectious: may be related to dry eye disease, minor trauma, contact lens irritation, exposure to chemicals, or immune reactions.

Some forms of keratitis may be mild and cause irritation, while others can progress more quickly and may require urgent professional intervention to protect vision.

Prevalence of Infective Keratitis: Causative Organisms by Region

The organisms responsible for infective keratitis vary considerably by region, largely reflecting differences in climate and environmental exposure.

In the UK, bacterial infection dominates, with fungal and Acanthamoeba keratitis remaining rare. In Ladan, Nepal, fungal keratitis accounts for over a third of cases, reflecting a broader global pattern where fungal keratitis is more common in tropical, agricultural regions, while bacterial keratitis predominates in higher-income settings, often linked to contact lens wear.

Common Risk Factors for All Types of Keratitis

• Contact lens use: Can disrupt the corneal surface and trap contaminants, especially if the fitting is poor or hygiene is inadequate.
• Corneal surface damage or irritation: Allows infection or inflammation to develop more easily.
• Dry eye or reduced tear production and protection: Weakens the eye’s natural cleansing, lubricating and defence mechanisms.
• Weakened immune response: Reduces the eye’s ability to control inflammation or infection.
• Poor eyelid hygiene or chronic eyelid inflammation: Increases irritation near the corneal surface as well as risk of infection.

6 Types of Keratitis

1. Bacterial Keratitis

Bacterial keratitis is an infectious condition in which bacteria invade the cornea, often progressing quickly if there is no timely treatment.

Common Risk Factors

• Contact lens use: Increases exposure to surface contamination.
• Corneal surface damage: Creates entry points for infection.
• Reduced or poor tear film and ocular surface quality: Limits natural surface cleansing.

Causes

• Poor contact lens hygiene: Allows harmful organisms to reach the cornea.
• Sleeping in contact lenses: Reduces oxygen supply and weakens surface defence.
• Minor eye injuries: Create small breaks in the cornea’s surface that allow infection.

Symptoms to Watch Out For

• Sudden eye redness
• Eye pain or discomfort
• Discharge
• Blurred vision

2. Fungal Keratitis

Fungal keratitis is a corneal infection that may be overlooked or mistaken for other types of infection in the early stages.

Common Risk Factors

• Corneal trauma: Disrupts the protective surface of the eye.
• Steroid eye drop use: Lowers local immune defence.
• Reduced immunity: Slows infection control and healing.

Causes

• Eye injury involving plant material or soil: Increases exposure to environmental organisms.
• Systemic health conditions: Reduce the body’s ability to fight infection.

Symptoms to Watch Out For

• Gradual eye redness (can also be sudden)
• Persistent discomfort or pain
• Blurred vision
• Light sensitivity

3. Acanthamoeba Keratitis

Acanthamoeba keratitis is a rare but serious corneal infection most commonly linked to contact lens wear and water exposure.

Common Risk Factors

• Contact lens wear: Increases surface exposure risk, especially if in contact with water.
• Poor lens hygiene: Raises the chance of contamination.
• Corneal irritation: Makes the surface more vulnerable.

Causes

• Exposure of lenses to water: Water sources may carry harmful organisms.
• Swimming or showering with lenses: Allows contamination to adhere to lenses.
• Use of non-sterile solutions: Reduces lens safety and cleanliness.

Symptoms to Watch Out For

• Severe eye pain
• Redness
• Blurred vision
• Marked light sensitivity

4. Microbial Keratitis

Microbial keratitis is a general term for corneal infections caused by different types of microorganisms.

Common Risk Factors

• Contact lens misuse: Increases exposure and surface damage.
• Eye trauma: Compromises corneal integrity.
• Reduced immune defence: Limits infection control.

Causes

• Breakdown of corneal surface protection: Allows organisms to initiate infection.
• Previous eye surgery or surface disease: Alters normal healing and defence.

Symptoms to Watch Out For

• Increasing redness
• Eye pain
• Discharge
• Worsening vision, sudden or gradual

5. Marginal Keratitis

Marginal keratitis is an inflammatory condition affecting the outer edge of the cornea and is usually “sterile” rather than a direct or active infection. It may be referred to as a “sterile ulcer”.

Common Risk Factors

• Chronic eyelid inflammation: Chronic blepharitis, often staphylococcal, triggers immune responses.
• Poor eyelid hygiene: Other bacteria on the eye lid margin can trigger the inflammation.
• Certain skin conditions: Rosacea can have eyelid and eye inflammatory associations.

Causes

• Chronic eyelid and lid margin disease: The peripheral cornea is involved in a hypersensitivity reaction to triggers from lid margin inflammation or bacterial load.

Symptoms to Watch Out For

• Redness near the corneal edge
• Mild discomfort
• Light sensitivity
• Eye irritation

6. Superficial Punctate Keratitis

Superficial punctate keratitis involves tiny surface defects of the cornea caused by dryness or irritation.

Common Risk Factors

• Dry eye disease: Reduces surface lubrication and protection.
• Reduced blinking: Limits tear distribution across the cornea.
• Environmental exposure: Accelerates tear evaporation.

Causes

• Prolonged screen use: Decreases blink rate and tear spread.
• Contact lens irritation: Causes surface micro-damage.
• Wind or air conditioning: Dries the eye surface.

Symptoms to Watch Out For

• Burning or stinging
• Gritty or foreign body sensation
• Light sensitivity
• Intermittent blurred vision

7. Viral Keratitis

Viral keratitis is corneal infection or inflammation caused by a virus, most commonly adenovirus, herpes simplex, herpes zoster, or cytomegalovirus.

Common Risk Factors

• Prior herpes infection: Latent HSV or VZV can reactivate and travel to the cornea.
• Weakened immune system: Limits the body’s ability to control viral activity.
• Stress, illness, or UV exposure: Known triggers for herpetic reactivation.

Causes

• Reactivation of latent HSV or VZV: The virus travels along nerve tissue to the eye during a flare-up.
• Adenoviral spread: Highly contagious, typically spread through contaminated hands or surfaces.
• Immunosuppression: Strongly linked to cytomegalovirus keratitis in particular.

Symptoms to Watch Out For

• Eye redness and irritation
• Watery discharge
• Light sensitivity
• Blurred vision, sometimes with a dendritic (branching) ulcer pattern

How Keratitis Is Diagnosed

Keratitis is diagnosed by an eye care professional through a comprehensive eye examination, which may include the following tests:

• Visual Acuity Test: Assesses how clearly you can see and whether vision has been affected.
• Slit-Lamp Examination: Uses a specialised microscope to examine the cornea in high detail.
• Fluorescein Staining Test: A dye test that highlights corneal surface damage or ulcers.
• Corneal Scraping or Swab Test: In suspected infectious keratitis, a small sample is taken to help identify the underlying cause and organism and guide treatment.

Accurate diagnosis helps guide appropriate keratitis treatment and can reduce the risk of complications such as corneal scarring or vision loss.

Keratitis Treatment Options

*Treatment approaches vary based on individual assessment and should always be guided by a qualified eye care professional.

When to See an Eye Specialist

Consult an eye care professional promptly if you experience:

• Sudden, persistent or worsening eye redness or pain
• Sudden or worsening blurred vision
• Sensitivity to light
• Discharge from the eye
• A feeling that something is in the eye that does not improve
• Symptoms that appear or worsen while wearing or on removal of contact lenses

Contact lens wearers should be particularly cautious, as some forms of microbial keratitis can progress and may cause lasting damage if not treated appropriately.

If you suspect a serious eye problem, or if symptoms are severe or sudden in onset, seek urgent eye care or visit an emergency service as advised in your region.

Conclusion

Keratitis is an inflammatory condition of the cornea that can range from mild irritation to serious infection, making early recognition and professional evaluation essential. Understanding the different types of keratitis, common symptoms, possible causes, and general treatment approaches helps patients seek timely care and reduce the risk of complications. With prompt diagnosis and appropriate management guided by an eye care professional, most cases of keratitis can be treated effectively while protecting long-term vision.

Concerned About Possible Keratitis?

Early evaluation helps protect long-term vision. Schedule a detailed eye examination at AccuVision for accurate diagnosis and personalised guidance.

FAQs

1. Is keratitis the same as a corneal ulcer?
Not always. Keratitis refers to inflammation of the cornea, while a corneal ulcer is an open sore that can develop in more severe cases of keratitis, such as advanced bacterial or fungal infections. Marginal keratitis can sometimes be called a sterile ulcer. All types of red eye require professional evaluation.

2. Can keratitis go away on its own?
Mild, non-infectious keratitis related to dryness or minor irritation may improve with lubrication. However, infectious keratitis, including bacterial, fungal, or Acanthamoeba keratitis, usually does not resolve on its own and requires professional treatment.

3. Can I shower in my contact lenses?
It’s best avoided. Water contains microorganisms, including Acanthamoeba, that can adhere to lenses and lead to serious infection.

4. Can I swim with my contact lenses?
No, this isn’t recommended, as it significantly increases the risk of Acanthamoeba keratitis and other infections. If swimming is unavoidable, wearing tightly sealed goggles and discarding or thoroughly disinfecting lenses afterwards is advised.

5. Can I sleep in my contact lenses?
Sleeping in lenses reduces oxygen supply to the cornea and weakens its natural defences, raising the risk of bacterial keratitis. Only sleep in lenses specifically approved for overnight wear, and only as directed by your eye care professional.

Reference

Stapleton, F. (2023) ‘The epidemiology of infectious keratitis’, The Ocular Surface, 28, pp. 351–363.