Corneal Ulcer: Symptoms, Causes, Emergency Treatment and Prevention

Author: Dr Val Phua
Estimated reading time: 20 minutes

A corneal ulcer is an open sore on the cornea—the clear, dome-shaped surface at the front of the eye.

Corneal ulcers are commonly caused by infection and may progress rapidly. Without prompt diagnosis and appropriate treatment, an ulcer can cause:

Permanent corneal scarring
Irregular astigmatism
Severe loss of vision
Corneal thinning
A hole in the cornea
Infection inside the eye
The need for emergency corneal transplantation
Rarely, loss of the eye

A painful red eye with blurred vision or marked light sensitivity should therefore never be assumed to be ordinary conjunctivitis, dry eye or contact-lens irritation.

This is particularly important for contact-lens wearers. Contact-lens use is a major risk factor for microbial keratitis in developed countries, and sleeping, swimming or showering in lenses substantially increases the risk of serious infection.

A corneal ulcer is an ophthalmic emergency. Treatment may need to begin immediately, sometimes with antibiotic or antimicrobial eyedrops used every hour around the clock.

The Quick Answer

What Is a Corneal Ulcer?

A corneal ulcer is an area where the surface epithelium of the cornea has broken down, usually with inflammation or infection in the underlying corneal tissue.

The term is often used interchangeably with infectious keratitis or microbial keratitis, although not every corneal ulcer is infectious.

A typical infectious ulcer includes:

An epithelial defect or open sore
A white or grey inflammatory infiltrate in the cornea
Surrounding corneal swelling
Eye redness
Pain or irritation
Inflammation inside the front of the eye

Bacteria, fungi, Acanthamoeba and viruses can all cause infectious keratitis.

What Are the Main Symptoms?

Possible symptoms include:

Eye pain
Increasing redness
Blurred or reduced vision
Marked sensitivity to light
Watering
Discharge
A feeling that something is stuck in the eye
Difficulty opening the eye
Eyelid swelling
A visible white spot on the cornea
Contact-lens intolerance

The symptoms may worsen within hours, particularly with aggressive bacterial infections.

Is a Corneal Ulcer an Emergency?

Yes.

Arrange urgent same-day ophthalmic assessment for:

A painful red eye
Reduced vision
Significant light sensitivity
A white or cloudy corneal spot
Redness or pain in a contact-lens wearer
Symptoms that worsen after an eye injury
Failure of a presumed abrasion to improve
Increasing pain despite antibiotic treatment

Delayed diagnosis and inappropriate treatment can lead to permanent visual impairment, blindness or loss of the eye.

Should Contact Lenses Be Removed?

Yes.

Remove the contact lens immediately and do not reinsert it.

Keep the following items when possible because they may help with microbiological investigation:

The lens
The lens case
The cleaning solution
The solution bottle

Do not rinse them with tap water.

Can a Corneal Ulcer Heal Completely?

Some small, peripheral ulcers heal with little or no lasting visual effect.

Other ulcers leave:

A corneal scar
Irregular corneal shape
Reduced contrast
Glare
Astigmatism
Permanent visual loss

The outcome depends on:

The organism
Ulcer size and depth
Whether the visual axis is involved
How quickly treatment begins
Antimicrobial susceptibility
Ocular-surface health
Treatment adherence
Whether the cornea perforates

Understanding the Cornea

What Is the Cornea?

The cornea is the transparent front surface of the eye.

It lies in front of:

The iris
The pupil
The natural lens

The cornea provides much of the eye’s focusing power and must remain:

Clear
Smooth
Regularly shaped
Free from significant swelling or scarring

Even a small central corneal scar can have a major effect on vision.

The Main Corneal Layers

The cornea includes:

Epithelium
Bowman’s layer
Stroma
Descemet’s membrane
Endothelium

Most corneal ulcers begin with a break in the epithelium. Microorganisms can then enter the underlying stroma and trigger infection and inflammation.

Why Does Infection Progress Quickly?

The cornea is normally protected by:

An intact epithelium
Blinking
Tears
Antimicrobial tear components
Eyelid closure
Immune defences

When these defences are disrupted, organisms may multiply within corneal tissue.

Inflammatory enzymes released by microorganisms and immune cells can damage the corneal collagen, causing rapid thinning or perforation.

Corneal Ulcer, Keratitis and Corneal Abrasion

Corneal Abrasion

A corneal abrasion is a superficial scratch or loss of epithelium.

Possible causes include:

A fingernail
Paper
A tree branch
Dust
A foreign body
Contact-lens trauma

An uncomplicated abrasion does not initially contain a stromal infectious infiltrate.

However, infection can develop within a damaged area, particularly after:

Contact-lens wear
Soil or vegetative trauma
Delayed treatment
Steroid use
Exposure to contaminated water

Keratitis

Keratitis means inflammation of the cornea.

It may be:

Infectious
Immune-mediated
Exposure-related
Neurotrophic
Toxic
Associated with severe dry eye

Corneal Ulcer

A corneal ulcer usually refers to an epithelial defect with underlying stromal inflammation or tissue loss.

A clinician must determine whether the ulcer is:

Bacterial
Fungal
Acanthamoeba-related
Viral
Sterile or immune-mediated
A combination of more than one process

The treatments are very different, and an incorrect treatment—particularly unsupervised steroid use—can worsen infection.

Common Symptoms

Eye Pain

Pain may range from mild irritation to severe, disabling pain.

The severity does not always correspond to the ulcer’s size.

Acanthamoeba keratitis may cause pain that appears disproportionately severe compared with the initial clinical findings, although this classic feature is not present in every case.

Redness

The eye may appear diffusely red or intensely red around the cornea.

Increasing redness despite treatment may indicate progression.

Light Sensitivity

Photophobia may be caused by:

Corneal nerve stimulation
Inflammation inside the eye
Ciliary spasm
Corneal epithelial disruption

Marked light sensitivity is an important warning symptom.

Reduced Vision

Vision may be affected by:

A central ulcer
Corneal swelling
Inflammation
Irregular astigmatism
Discharge
Anterior-chamber reaction
Corneal scarring
Perforation

A peripheral ulcer may initially have less effect on central visual acuity.

Watering

Reflex tearing is common because the cornea contains many sensory nerves.

Discharge

Bacterial ulcers may produce:

Mucus
Pus
Sticky discharge
Eyelashes sticking together

However, the absence of discharge does not exclude infection.

Foreign-Body Sensation

Patients may feel that:

Sand is trapped in the eye
A contact lens remains inside
An eyelash is rubbing the cornea
Something is scratching with every blink

A White Spot

A white, grey or cream spot on the cornea may represent:

An inflammatory infiltrate
Infection
Necrotic tissue
A developing scar

A visible white corneal spot associated with pain, redness or reduced vision requires urgent examination.

Main Causes of Corneal Ulcers

Bacterial Keratitis

Bacterial infection is a common cause of acute microbial keratitis.

Common organisms include:

Pseudomonas aeruginosa
Staphylococcus species
Streptococcus species
Serratia species
Enteric gram-negative bacteria
Less common or resistant organisms

Contact-lens wear is a major risk factor, and Pseudomonas is especially important in contact-lens-related infection because it can progress rapidly.

Fungal Keratitis

Fungal ulcers may be caused by filamentous fungi such as:

Fusarium
Aspergillus

or yeast such as:

Candida

Fungal keratitis is particularly associated with:

Trauma involving plants or soil
Agricultural work
Tropical climates
Chronic ocular-surface disease
Steroid use
Immunosuppression
Contact-lens wear

Diagnosis and treatment may be difficult, and prolonged antifungal therapy or corneal surgery may be required.

Acanthamoeba Keratitis

Acanthamoeba is a microscopic free-living organism found in:

Tap water
Fresh water
Salt water
Soil
Dust
Swimming pools
Hot tubs
Water systems

Most cases in developed settings occur in contact-lens wearers, particularly when lenses are exposed to water or handled with poor hygiene.

Acanthamoeba infection can cause severe pain, prolonged inflammation, corneal ulceration and permanent visual loss. Early diagnosis is associated with better outcomes.

Herpes Simplex Keratitis

Herpes simplex virus can affect the corneal epithelium and cause a branching, dendritic ulcer.

The virus may remain dormant and reactivate later.

HSV may also affect deeper corneal layers, causing:

Stromal inflammation
Corneal thinning
Scarring
Reduced corneal sensation
Anterior uveitis

Treatment varies according to the corneal layer involved. Antivirals are central to management, while steroid use must be carefully supervised and is inappropriate for untreated active epithelial viral disease.

Herpes Zoster Keratitis

Shingles affecting the ophthalmic division of the trigeminal nerve may involve the:

Eyelids
Conjunctiva
Cornea
Iris
Retina
Optic nerve

Corneal complications may occur during the initial illness or later.

Sterile Corneal Ulceration

Not every corneal ulcer is caused by microorganisms.

Sterile inflammatory ulcers may occur with:

Severe dry eye
Rheumatoid arthritis
Peripheral ulcerative keratitis
Mooren ulcer
Contact-lens-related inflammatory infiltrates
Eyelid disease
Autoimmune vasculitis
Medication toxicity

Sterile and infectious ulcers can resemble one another and may coexist. Infectious causes should be excluded before immunosuppressive treatment is intensified.

Risk Factors

Contact-Lens Wear

Contact-lens wear is one of the most important risk factors for microbial keratitis.

Risk increases with:

Sleeping or napping in lenses
Extended wear
Swimming in lenses
Showering in lenses
Rinsing lenses with water
Storing lenses in water
Topping up old solution
Poor case hygiene
Delayed lens replacement
Wearing lenses beyond the recommended duration
Buying lenses without proper professional fitting
Continuing to wear lenses despite pain or redness

Sleeping in contact lenses increases the risk of contact-lens-related eye infection by approximately six- to eightfold.

Water Exposure

Tap water is safe to drink in many countries but is not sterile.

Water may contain microorganisms capable of contaminating:

Contact lenses
Lens cases
The corneal surface

Contact lenses should be removed before swimming, showering or using a hot tub. They should never be rinsed or stored in water.

Eye Trauma

Corneal injury creates an entry point for infection.

Trauma involving:

Soil
Plant material
Wood
Agricultural debris

should raise suspicion for fungal keratitis as well as bacterial infection.

Foreign Bodies

A retained corneal foreign body or contaminated material beneath the eyelid can damage the epithelium and introduce infection.

Severe Dry Eye

An unhealthy or poorly protected corneal surface is more vulnerable to:

Epithelial breakdown
Infection
Non-healing ulcers
Corneal melting

Eyelid Disease

Conditions such as:

Blepharitis
Entropion
Trichiasis
Incomplete eyelid closure
Facial-nerve weakness

may repeatedly traumatise or contaminate the cornea.

Reduced Corneal Sensation

Corneal sensation may be reduced by:

Herpes infection
Diabetes
Previous eye surgery
Trigeminal-nerve disease
Long-term topical medication
Neurotrophic keratopathy

A patient with reduced sensation may develop a severe ulcer with surprisingly little pain.

Previous Eye Surgery

Risk may be increased after:

Corneal transplantation
LASIK or PRK
Cataract surgery
Glaucoma surgery
Retinal surgery

especially when there is:

A loose or broken corneal suture
Persistent epithelial breakdown
Long-term steroid use
Ocular-surface disease

Steroid Eyedrops

Steroids suppress inflammation but may also reduce the eye’s ability to control infection.

Unsupervised steroid use can:

Worsen bacterial infection
Cause fungal or Acanthamoeba infection to progress
Enlarge a herpes epithelial ulcer
Mask clinical signs
Delay healing

Steroids should not be started for a suspected corneal ulcer without specialist guidance.

Diabetes and Immunosuppression

Risk and severity may be increased by:

Poorly controlled diabetes
Immunosuppressive medication
Cancer treatment
HIV-related immunosuppression
Severe systemic illness

Contaminated or Unregulated Eye Products

Potential risks include:

Non-sterile eyedrops
Traditional eye remedies
Saliva applied to the eye
Shared eye medication
Contaminated cosmetic products
Unregulated contact lenses

Contact-Lens-Related Corneal Ulcers

Why Can Contact Lenses Cause Infection?

A contact lens may:

Reduce oxygen reaching the cornea
Create microscopic epithelial trauma
Trap microorganisms against the surface
Alter blinking and tears
Develop deposits or biofilm
Transfer contamination from fingers, cases or water

The risk is much greater when recommended care and replacement practices are not followed.

Why Is Sleeping in Lenses Dangerous?

During sleep:

Oxygen delivery is reduced
Blinking stops
Tear exchange decreases
Microorganisms remain trapped
The epithelial barrier may become more vulnerable

Even lenses approved for extended wear do not eliminate infection risk.

Daily Disposable Lenses

Daily disposables remove the need for a storage case and daily disinfection.

However, they can still cause infection if the wearer:

Sleeps in them
Reuses them
Exposes them to water
Handles them with unwashed hands
Continues wearing them during symptoms

Orthokeratology Lenses

Overnight orthokeratology lenses are deliberately worn during sleep.

Strict fitting, cleaning, follow-up and water avoidance are essential. Both bacterial and Acanthamoeba infections have been reported with orthokeratology wear.

Bacterial Corneal Ulcers

Typical Appearance

A bacterial ulcer may show:

A dense white or yellow infiltrate
An overlying epithelial defect
Corneal swelling
Mucopurulent discharge
Anterior-chamber inflammation
A hypopyon

A hypopyon is a collection of inflammatory white cells visible in the lower part of the anterior chamber.

How Quickly Can It Progress?

Some bacterial ulcers progress over hours.

Pseudomonas infection may cause rapid stromal destruction, particularly in contact-lens wearers.

Initial Treatment

Treatment commonly begins immediately with intensive topical antibiotics.

Options may include:

A broad-spectrum fluoroquinolone
Fortified antibiotics combining coverage for gram-positive and gram-negative organisms
Treatment tailored to local resistance patterns and clinical severity

Drops may initially be required:

Every 30 to 60 minutes
Through the night
After a loading phase of very frequent administration

The exact regimen must be prescribed by the treating ophthalmologist.

Why Are Drops Given So Frequently?

Eyedrops remain on the ocular surface for a limited time.

Frequent treatment is needed to achieve effective antimicrobial concentrations within the infected cornea.

Can Oral Antibiotics Treat It?

Oral antibiotics alone generally do not provide adequate treatment for an ordinary bacterial corneal ulcer.

They may be added for:

Scleral extension
Risk of perforation
Gonococcal infection
Infection involving surrounding tissue
Specific systemic indications

Fungal Corneal Ulcers

When Should Fungal Infection Be Suspected?

Suspicion is higher after:

Plant or soil trauma
Agricultural injury
Chronic steroid use
Infection that responds poorly to antibiotics
Contact-lens contamination
Immunosuppression

Typical Clinical Features

Possible features include:

A dry or raised infiltrate
Feathery margins
Satellite infiltrates
An immune ring
Endothelial plaque
Hypopyon

These features are suggestive but are not reliable enough to replace laboratory testing.

Antifungal Treatment

Topical antifungals are the mainstay of treatment.

For filamentous fungal keratitis, topical natamycin is commonly used first-line. The MUTT I randomised trial found better clinical and microbiological outcomes with natamycin than topical voriconazole for smear-positive filamentous fungal ulcers, particularly those caused by Fusarium.

Additional treatment may include:

Other topical antifungals
Oral antifungal medication
Intrastromal medication
Intracameral medication
Repeated corneal scraping
Therapeutic corneal transplantation

Treatment is often prolonged because fungal organisms may extend deeply into corneal tissue.

Why Are Steroids Dangerous?

Steroids can allow fungal organisms to proliferate and may worsen thinning or delay diagnosis.

They should not be used unless specifically directed by a corneal specialist after the infection is controlled and the diagnosis is secure.

Acanthamoeba Corneal Ulcers

Who Is at Risk?

Risk is strongly associated with:

Contact-lens wear
Water exposure while wearing lenses
Rinsing or storing lenses in water
Poor lens-case hygiene
Homemade saline
Swimming, hot tubs or showering in lenses
Corneal trauma involving contaminated water or soil

Why Is Diagnosis Often Delayed?

Acanthamoeba keratitis may resemble:

Herpes keratitis
Bacterial keratitis
Fungal keratitis
Contact-lens inflammation

Misdiagnosis and treatment delay remain common and are associated with poorer outcomes.

Possible Signs

Clinical findings may include:

Severe pain
Small epithelial abnormalities
Pseudodendrites
Perineural infiltrates
Multifocal stromal infiltrates
A ring infiltrate
Persistent inflammation

A ring infiltrate is often a later finding and should not be awaited before considering the diagnosis.

Treatment

Treatment commonly uses anti-amoebic agents such as:

Polyhexamethylene biguanide
Chlorhexidine
A diamidine in selected regimens

Treatment may continue for many months.

Acanthamoeba can form resistant cysts within the cornea, making eradication difficult and allowing relapse.

Surgery

Advanced cases may require:

Epithelial debridement
Amniotic-membrane treatment
Therapeutic corneal transplantation
Other reconstructive procedures

Early diagnosis—within approximately two weeks of symptoms in one recent series—was associated with better final visual outcomes.

Herpes Corneal Ulcers

Epithelial Herpes Keratitis

HSV epithelial keratitis may produce a dendritic ulcer with branching lines and terminal bulbs.

Treatment may include:

Topical antiviral medication
Oral antiviral medication
Gentle epithelial debridement in selected cases

Stromal Herpes Keratitis

Deeper herpetic disease may involve:

Stromal inflammation
Corneal swelling
Ulceration
Blood-vessel growth
Scarring
Anterior uveitis

Treatment often requires antiviral cover and carefully monitored anti-inflammatory treatment.

Why Should Steroid Use Be Supervised?

Steroids may be beneficial in selected stromal disease but can dramatically worsen active untreated epithelial herpes.

A steroid-antibiotic combination drop should never be self-started for an undiagnosed painful red eye.

How Is a Corneal Ulcer Diagnosed?

Symptom and Risk-Factor History

The ophthalmologist will ask about:

Contact-lens wear
Overnight lens use
Water exposure
Eye injury
Plant or soil trauma
Previous herpes infection
Eyedrop use
Steroid use
Eye surgery
Dry eye
Diabetes
Immune suppression
Previous treatment

Bring all eyedrops and contact-lens products to the appointment when possible.

Visual-Acuity Testing

Vision is measured before treatment when possible.

This provides:

A baseline
An indication of severity
Information about central involvement

Slit-Lamp Examination

The slit lamp is used to assess:

Ulcer location
Epithelial-defect size
Infiltrate size and depth
Corneal thinning
Surrounding oedema
Anterior-chamber inflammation
Hypopyon
Eyelid and tear-film disease

The lesion may be measured and documented with drawings or photographs.

Fluorescein Dye

Fluorescein highlights areas where the corneal epithelium is missing.

It may reveal:

The shape of the ulcer
A dendritic herpes pattern
A larger epithelial defect than is visible without dye
Leakage through a corneal perforation

Corneal Scraping

A sample may be taken from the ulcer using a sterile blade, needle or other instrument.

Testing may include:

Gram stain
Fungal stain
Bacterial culture
Fungal culture
Acanthamoeba culture
Antimicrobial susceptibility testing

Corneal scraping is especially important for ulcers that are:

Large
Central
Deep
Rapidly progressive
Atypical
Associated with significant thinning
Unresponsive to initial treatment
Suspected to be fungal or Acanthamoeba-related

Culture of corneal scrapings remains the preferred initial laboratory test for identifying the causative organism.

Polymerase Chain Reaction

PCR may help detect:

Herpes viruses
Acanthamoeba
Bacteria
Fungi

It is particularly useful when:

Prior treatment has reduced culture yield
The clinical appearance is atypical
A difficult-to-culture organism is suspected

In Vivo Confocal Microscopy

Confocal microscopy provides high-resolution imaging within the living cornea.

It may help identify:

Acanthamoeba cysts
Fungal filaments
Corneal nerve changes

It is a useful complementary investigation but is not available in every centre.

Contact-Lens and Case Cultures

The treating team may culture:

The lens
The lens case
The solution

These results may support the diagnosis, although organisms found in the case do not always prove which organism is causing the corneal infection.

Treatment Principles

Treatment Should Begin Promptly

For a sight-threatening ulcer, treatment may begin immediately after diagnostic samples are taken.

Waiting several days for culture results before starting therapy can allow irreversible damage.

Intensive Eyedrops

The first phase may require treatment:

Every hour
Day and night
With more than one medication

The frequency is gradually reduced as the ulcer responds.

Treatment Is Adjusted Over Time

The ophthalmologist assesses:

Pain
Visual acuity
Epithelial-defect size
Infiltrate size
Infiltrate density
Corneal thinning
Anterior-chamber inflammation
Culture results

Treatment may be changed when:

The organism is identified
Resistance is found
The ulcer worsens
Medication toxicity develops
Another diagnosis becomes more likely

Follow-Up May Be Daily

Severe ulcers may require:

Daily examination
Review more than once daily
Hospital admission
Close nursing support

Missing early follow-up can be dangerous even when the eye initially feels slightly better.

Steroids in Bacterial Corneal Ulcers

Are Steroids Always Avoided?

No.

In selected culture-confirmed bacterial ulcers, a corneal specialist may add topical corticosteroids after effective antibiotics have been started.

The purpose is to reduce:

Harmful inflammation
Scarring
Visual-axis damage

What Does the Evidence Show?

The Steroids for Corneal Ulcers Trial found no overall improvement in three-month best-corrected vision when adjunctive topical corticosteroids were added to antibiotic treatment, although subgroup and timing analyses suggest that selected patients may benefit.

When Are Steroids Dangerous?

Steroids should generally be avoided or used with extreme caution when:

Fungal keratitis is possible
Acanthamoeba is possible
Active epithelial herpes is present
The infection is uncontrolled
Corneal thinning is progressing
The organism is uncertain

Do not use steroid drops unless the ophthalmologist treating the ulcer has specifically prescribed them.

Pain Control

Cycloplegic Drops

A cycloplegic drop may be prescribed to:

Relax the iris and ciliary body
Reduce painful spasm
Reduce inflammation-related discomfort
Prevent or reduce iris adhesions

These drops may temporarily cause:

Blurred near vision
Light sensitivity
A larger pupil

Oral Pain Relief

Oral pain medication may be used when appropriate.

Numbing Drops

Topical anaesthetic drops are useful during clinical examination.

They should not generally be supplied for repeated home use because frequent use may:

Delay epithelial healing
Mask deterioration
Cause corneal toxicity
Lead to severe corneal damage

When Is Hospital Admission Needed?

Admission may be considered when:

The ulcer is large or central
The infection is rapidly progressing
The patient cannot administer hourly drops
There is only one functioning eye
The cornea is significantly thinned
Perforation is threatened
Follow-up reliability is uncertain
A child is affected
Severe pain or disability prevents self-treatment
Social support is inadequate
Systemic or intravenous treatment is required

Corneal Thinning and Perforation

What Is Corneal Melting?

Corneal melting refers to progressive destruction and thinning of stromal tissue.

It can occur because of:

Severe infection
Microbial enzymes
Intense immune inflammation
Autoimmune disease
Medication toxicity

What Is a Corneal Perforation?

A perforation is a full-thickness hole in the cornea.

Fluid may leak from inside the eye, and internal structures may move towards or through the opening.

This is an emergency.

Treatment Options

Depending on the size and cause, treatment may include:

Tissue adhesive or corneal glue
A protective contact lens
Amniotic membrane
Conjunctival flap
Patch graft
Therapeutic corneal transplantation

Corneal Transplantation

When Is an Emergency Transplant Needed?

Therapeutic keratoplasty may be required when:

Infection progresses despite appropriate medication
The cornea is perforated
Perforation is imminent
Infection extends deeply
A large area of tissue is destroyed
The infected cornea cannot be sterilised medically

Fungal and Acanthamoeba infections are among the conditions that may require therapeutic transplantation when medical treatment fails.

Does the Transplant Restore Normal Vision Immediately?

The immediate purpose of a therapeutic transplant is often to:

Remove infection
Preserve the eye
Restore structural integrity

Final visual rehabilitation may require:

Glasses
Rigid or scleral contact lenses
Suture adjustment
Further surgery
Cataract treatment
A later optical graft

Signs That Treatment Is Working

Improvement may include:

Less pain
Reduced redness
Smaller epithelial defect
Less dense infiltrate
Sharper ulcer margins
Reduced anterior-chamber inflammation
Less discharge
Improved vision

Vision may remain blurred while the ulcer heals because of:

Swelling
Medication
Dilated pupil
Scar formation
Irregular surface

Signs That the Ulcer Is Worsening

Warning signs include:

Increasing pain
Increasing redness
Falling vision
Enlargement of the white infiltrate
Increasing corneal thinning
New satellite lesions
Larger hypopyon
Increasing discharge
New eyelid swelling
Failure to improve despite intensive treatment

Contact the treating clinic immediately rather than waiting for the next scheduled visit.

Possible Complications

Corneal Scarring

A scar may cause:

Blurred vision
Glare
Reduced contrast
Ghosting
Irregular astigmatism

Central scars are usually more visually significant than peripheral scars.

Corneal Vascularisation

Blood vessels may grow into the normally transparent cornea after severe or prolonged inflammation.

This can:

Reduce clarity
Increase future transplant-rejection risk
Cause lipid deposition

Irregular Astigmatism

Uneven healing can distort the corneal surface.

Ordinary spectacles may not fully correct irregular astigmatism.

Corneal Perforation

Severe thinning may create a full-thickness hole.

Endophthalmitis

Infection may rarely spread inside the eye, causing endophthalmitis.

This may require:

Intraocular antibiotics
Vitrectomy
Emergency surgery

Secondary Glaucoma

Eye pressure may rise because of:

Inflammation
Steroid treatment
Damage to drainage structures
Forward movement of internal eye structures

Cataract

Severe inflammation or prolonged steroid therapy may accelerate cataract formation.

Permanent Visual Loss

Visual loss may remain despite elimination of the infection because of:

Central scarring
Irregular corneal shape
Perforation
Glaucoma
Retinal or intraocular complications

Vision Rehabilitation After Healing

Glasses

Glasses may correct residual:

Short-sightedness
Long-sightedness
Regular astigmatism

Rigid or Scleral Contact Lenses

A rigid gas-permeable or scleral lens can create a smooth optical surface over an irregular scar.

This may substantially improve vision when spectacles cannot fully correct the distortion.

Contact-lens use should resume only after:

Infection is fully resolved
The cornea is stable
The treating ophthalmologist approves
A specialist fitting has been performed

Corneal Laser Treatment

Selected superficial scars or irregularities may occasionally be treated with:

Phototherapeutic keratectomy
Other customised corneal procedures

Optical Corneal Transplantation

A later transplant may be considered when:

The eye is quiet
Infection has been eradicated
The scar is visually significant
Contact lenses do not provide adequate vision

Preventing Contact-Lens-Related Ulcers

Wash and Dry Your Hands

Use soap and water before touching contact lenses.

Dry the hands completely with a clean, lint-free towel.

Never Sleep in Lenses Unless Specifically Directed

Avoid naps and overnight wear unless the prescribing professional has explicitly advised it.

Even approved extended-wear lenses carry infection risk.

Keep Lenses Away From Water

Remove contact lenses before:

Showering
Swimming
Using a hot tub
Participating in water sports

Never rinse or store lenses in:

Tap water
Bottled water
Distilled water
Homemade saline

CDC guidance recommends keeping all water away from contact lenses.

Use Fresh Contact-Lens Solution

Never:

Top up yesterday’s solution
Reuse old solution
Transfer solution into a non-sterile container
Use expired solution

Rub and Rinse Reusable Lenses

Follow the care-system instructions and the advice of the fitting professional.

Care for the Lens Case

Clean the case with fresh disinfecting solution rather than water.

Allow it to air-dry upside down with the caps off.

Replace the case at least every three months or as advised.

Replace Lenses on Schedule

Do not extend a:

Daily disposable lens into a second day
Two-week lens for a month
Monthly lens beyond the recommended period

Keep Backup Glasses

Carry an up-to-date pair of spectacles so lenses can be removed immediately if the eyes become uncomfortable.

Attend Regular Reviews

Contact lenses are medical devices and should be fitted and monitored professionally.

What to Do When a Contact-Lens Eye Becomes Red

Remove the Lens Immediately

Do not wait to see whether the redness settles while continuing to wear it.

Do Not Reinsert Another Lens

Use glasses until the eye has been examined and cleared.

Seek Same-Day Assessment for Warning Symptoms

Urgent examination is required for:

Pain
Light sensitivity
Blurred vision
Discharge
Increasing redness
A white corneal spot
Symptoms persisting after the lens is removed

Keep the Lens and Case

Store them without adding tap water and bring them to the clinic if requested.

What Not to Do

Do Not Patch a Suspected Infectious Ulcer

An eye patch can create a warm, closed environment and may delay recognition of deterioration.

Do Not Use Leftover Eyedrops

An old antibiotic may:

Be expired
Be contaminated
Provide inadequate coverage
Reduce culture yield
Delay correct diagnosis

Do Not Use Steroid-Containing Drops Without Examination

Combination antibiotic-steroid drops can be particularly dangerous in:

Fungal keratitis
Acanthamoeba keratitis
Active herpes epithelial disease

Do Not Use Saliva or Traditional Remedies

Saliva and non-sterile products can introduce additional organisms.

Do Not Continue Contact-Lens Wear

A lens should not be used as a bandage unless specifically prescribed and monitored by an eye-care professional.

Do Not Stop Treatment When the Eye Feels Better

Symptoms may improve before the organism has been fully eradicated.

Antimicrobial treatment should be reduced only according to the treating ophthalmologist’s instructions.

Corneal Ulcers in Children

Possible Causes

Children may develop corneal ulcers because of:

Eye injury
Foreign bodies
Contact lenses
Orthokeratology
Eyelid abnormalities
Severe allergy and eye rubbing
Herpes infection
Vitamin deficiency in selected settings
Ocular-surface disease

Why Is Assessment More Difficult?

Young children may not clearly report:

Pain
Light sensitivity
Reduced vision
Contact-lens habits
Trauma

Possible signs include:

Refusing to open the eye
Persistent watering
Redness
Eye rubbing
Avoiding light
A visible white spot
Reduced visual behaviour

Prompt specialist examination is important because central scarring can interfere with visual development and cause amblyopia.

Frequently Asked Questions

Is a Corneal Ulcer the Same as Conjunctivitis?

No.

Conjunctivitis primarily affects the conjunctiva, while a corneal ulcer involves the transparent cornea and can threaten sight.

Pain, reduced vision, marked light sensitivity or a white corneal spot are not typical features of uncomplicated conjunctivitis.

Can a Corneal Ulcer Heal Without Treatment?

A small non-infectious defect may occasionally heal, but a suspected infectious ulcer should never be left untreated.

The infection may worsen rapidly even when symptoms initially appear mild.

How Fast Can a Corneal Ulcer Worsen?

Aggressive bacterial ulcers may progress within hours.

Fungal and Acanthamoeba infections may progress more slowly but remain extremely difficult to treat if diagnosis is delayed.

Can a Corneal Ulcer Cause Blindness?

Yes.

Severe infection may cause central scarring, perforation, endophthalmitis or loss of the eye.

Will I Need to Use Eyedrops Overnight?

Possibly.

Severe ulcers commonly require hourly treatment around the clock during the initial phase.

Why Must the Cornea Be Scraped?

Scraping helps identify the causative organism and determine which medication is most likely to work.

Does Scraping Hurt?

The eye is numbed before the procedure.

Patients may feel pressure or mild irritation rather than sharp pain.

Why Are My Culture Results Negative?

Possible reasons include:

Prior antibiotic treatment
A small sample
Low organism numbers
An organism that is difficult to culture
A non-infectious ulcer

A negative culture does not automatically exclude infection.

Can Antibiotics Treat a Fungal Ulcer?

No.

Fungal infections require antifungal medication.

Using only antibacterial drops may delay appropriate treatment.

Can a Steroid Help the Pain and Redness?

Steroids can reduce inflammation but may worsen uncontrolled infection.

They should be used only under specialist supervision.

How Long Does Treatment Take?

Treatment may last:

Days to weeks for selected bacterial ulcers
Several weeks for severe bacterial infection
Weeks to months for fungal keratitis
Several months for Acanthamoeba keratitis

The duration depends on clinical response rather than a fixed schedule.

Can I Return to Contact Lenses After Healing?

Possibly, after the infection has completely resolved and the cornea is stable.

The lens type, fit, hygiene routine and previous risk behaviours should be reviewed carefully.

Do I Need to Throw Away My Contact Lenses?

The affected lens, case and opened solution should generally not be reused.

Follow the treating professional’s instructions regarding replacement of supplies.

Can Swimming Cause a Corneal Ulcer?

Swimming while wearing contact lenses increases exposure to waterborne microorganisms and should be avoided.

Can Tap Water Cause Acanthamoeba Keratitis?

Acanthamoeba may be present in tap water and other environmental water sources.

The greatest concern arises when contaminated water contacts a vulnerable cornea or contact lens.

Can a Corneal Ulcer Return?

Yes.

Recurrence may occur because of:

Continued unsafe contact-lens habits
Herpes reactivation
Persistent eyelid disease
Severe dry eye
Neurotrophic cornea
Incomplete eradication
A resistant organism
Ongoing steroid or immunosuppressive exposure

Will a Corneal Scar Fade?

Some scars become thinner and less dense over months.

A deep central scar may remain permanently.

Can a Corneal Transplant Restore Vision?

A transplant may preserve the eye or improve vision, but it does not guarantee normal sight.

Visual outcome depends on:

Retinal and optic-nerve health
Graft clarity
Astigmatism
Rejection risk
Recurrence of infection
Need for further procedures

When to Seek Emergency Eye Care

Seek same-day or emergency ophthalmic care for:

A painful red eye
Reduced or blurred vision
Severe light sensitivity
A white spot on the cornea
Increasing discharge
Eyelid swelling with eye pain
Contact-lens-related redness or pain
Symptoms after soil or plant injury
Worsening symptoms despite antibiotic drops
A presumed abrasion that is not improving
Recent steroid use with increasing redness
Sudden fluid leakage or change in the shape of the eye

Do not drive yourself when vision is significantly reduced.

A Corneal-Ulcer Emergency Checklist

Remove

Contact lenses
Eye makeup
Any non-prescribed eye product

Keep

The contact lens
Lens case
Cleaning solution
Medication bottles
Details of previous treatment

Avoid

Steroid drops
Eye patching
Tap-water rinsing
Saliva
Contact-lens reinsertion
Delaying care until the next day

Report

Tell the ophthalmologist about:

Overnight lens wear
Swimming or showering in lenses
Soil or plant trauma
Previous herpes infection
Steroid use
Diabetes or immunosuppression
Recent eye surgery
All medications already used

The Bottom Line

A corneal ulcer is an open sore in the cornea and is frequently caused by infection.

Possible causes include:

Bacteria
Fungi
Acanthamoeba
Herpes viruses
Severe inflammatory or ocular-surface disease

The most important symptoms are:

Eye pain
Redness
Reduced vision
Light sensitivity
Discharge
A visible white corneal spot

Contact-lens wear is a major risk factor, particularly when lenses are:

Worn overnight
Exposed to water
Reused improperly
Stored in contaminated cases
Worn beyond the replacement schedule

A corneal ulcer requires urgent ophthalmic assessment because delayed treatment can lead to:

Scarring
Irregular astigmatism
Perforation
Endophthalmitis
Emergency transplantation
Permanent visual loss

Treatment may involve:

Hourly antibiotic drops
Antifungal drops
Anti-Acanthamoeba medication
Antiviral treatment
Cycloplegic drops
Hospital admission
Corneal surgery

Do not self-treat a painful red eye with leftover antibiotic or steroid drops.

The safest rule is:

A contact-lens wearer with eye pain, redness, light sensitivity or blurred vision should remove the lens and arrange urgent same-day eye assessment.

References

Rhee MK, et al. Bacterial Keratitis Preferred Practice Pattern®. Ophthalmology. 2024. American Academy of Ophthalmology.
Cabrera-Aguas M, Khoo P, Watson SL. Infectious keratitis: a review. Clin Exp Ophthalmol. 2022;50(5):543–562. doi:10.1111/ceo.14113. PMID: 35610943.
Bourcier T, Sauer A, Dory A, et al. Bacterial keratitis: retrospective and prospective 2024. J Fr Ophtalmol. 2024. PMID: 39454484.
Awad R, Abdelbaky SH. Fungal keratitis: diagnosis, management and recent advances. Clin Ophthalmol. 2024. PMID: 38223815.
Prajna NV, Krishnan T, Mascarenhas J, et al. The Mycotic Ulcer Treatment Trial: a randomized trial comparing natamycin versus voriconazole. JAMA Ophthalmol. 2013;131(4):422–429. doi:10.1001/jamaophthalmol.2013.1497. PMID: 23710492.
Garg D, Halder S, Bhardwaj G, et al. A comprehensive review on Acanthamoeba keratitis: an overview of epidemiology, risk factors and therapeutic strategies. Cureus. 2024;16. PMID: 39328676.
Kanda T, Miyazaki D, Sasaki SI, et al. Clinical outcomes and prognostic factors in Acanthamoeba keratitis. Ocul Surf. 2024. PMID: 38220498.
Srinivasan M, Mascarenhas J, Rajaraman R, et al. Corticosteroids for bacterial keratitis: the Steroids for Corneal Ulcers Trial. Arch Ophthalmol. 2012;130(2):143–150. doi:10.1001/archophthalmol.2011.315. PMID: 21987582.
Srinivasan M, Mascarenhas J, Rajaraman R, et al. The Steroids for Corneal Ulcers Trial: long-term clinical outcomes. JAMA Ophthalmol. 2014;132(1):34–40. PMID: 24315294.
Suresh L, Ting DSJ, Said DG, et al. Clinical features, risk factors and outcomes of contact-lens-related bacterial keratitis. Eye. 2024.
Xu C, Lim CHL, Mehta JS. Update in management of microbial keratitis associated with contact-lens wear. Curr Opin Ophthalmol. 2025. PMID: 40277198.
Cope JR, Konne NM, Jacobs DS, et al. Corneal infections associated with sleeping in contact lenses—six cases, United States, 2016–2018. MMWR Morb Mortal Wkly Rep. 2018;67:877–881.
Centers for Disease Control and Prevention. Preventing eye infections when wearing contacts. Updated May 27, 2025.
Pusnik A, Petrovski G, Lumi X. Dysphotopsias or unwanted visual phenomena after cataract surgery. Life. 2023;13:53. PMID: 36676002.
Maycock NJR, Jayaswal R. Update on Acanthamoeba keratitis: diagnosis, treatment and outcomes. Cornea. 2016;35(5):713–720. PMID: 26989955.