When Is a Red Eye a Corneal Infection?

Prof Donald Tan Tiang Hwee

MBBS(S'pore), FRCS(Glas), FRCS(Edin), FRCOphth(UK), FAMS

Ophthalmologist

Partner and Senior Consultant

Dr Chan Wing Kwong

MBBS(S'pore), MMed(Ophth), FRCS(Edin), FRCOphth, FAMS

Ophthalmologist

Partner and Senior Consultant

Dr Anna Tan Wee Tien

MBBS (S'pore), MMed (Ophth), MRCSEd, FAMS

Ophthalmologist

Partner and Senior Consultant

Have you ever woken up with a painful red eye and wondered whether it would settle on its own? While many cases of red eyes are caused by relatively minor conditions such as allergies or irritation, some may be a sign of a corneal infection that requires prompt specialist care.

Because corneal infections can progress rapidly and threaten vision if left untreated, recognising when symptoms may be more serious is important. Knowing when to seek specialist assessment can help prevent complications and preserve your long-term eye health.

What Is a Corneal Infection?

A corneal infection, also known as infectious keratitis, occurs when bacteria, viruses, fungi or parasites infect the cornea, the clear front surface of the eye. The infection causes inflammation that can damage the normally transparent cornea and, in severe cases, lead to permanent scarring or vision loss.

Although some infections develop after an eye injury, many occur in people who wear contact lenses. Prompt diagnosis allows appropriate treatment to begin before the infection becomes more extensive.

What Causes Corneal Infections?

Different microorganisms can cause corneal infections, and identifying the underlying cause helps determine the most appropriate treatment.

Contact Lens-Related Infections

Contact lens wear is one of the most common risk factors. Sleeping in contact lenses, poor lens hygiene, using expired solutions or exposing lenses to tap water or swimming pools can increase the risk of infection.

Eye Injuries

A scratch from a fingernail, tree branch or other foreign object can create an opening that allows microorganisms to enter the cornea. Even seemingly minor injuries should be monitored if symptoms worsen.

Existing Eye Conditions or Reduced Immunity

People with dry eye disease, previous corneal disease or conditions that affect the immune system may be more susceptible to developing corneal infections. Long-term use of steroid eye drops may also increase the risk in certain situations.

Symptoms That Should Not Be Ignored

Not every red eye is an emergency, but certain symptoms suggest that specialist assessment should not be delayed.

These include:

• Moderate to severe eye pain
• Increasing redness that does not improve
• Blurred or reduced vision
• Sensitivity to light
• Excessive tearing or discharge
• A visible white or grey spot on the cornea
• Difficulty keeping the affected eye open

These symptoms may develop over hours or days. Because they can overlap with other eye conditions, an examination by an ophthalmologist is needed to establish the underlying cause.

How Corneal Infections Are Diagnosed

A specialist examination helps determine whether a corneal infection is present and identify the organism responsible where possible.

Detailed Eye Examination

Your ophthalmologist examines the cornea using a slit lamp microscope to assess the size, depth and location of the infection. This also helps identify whether complications have developed.

Corneal Sampling

For larger, more severe or unusual infections, a small sample may be taken from the affected area for laboratory testing. This allows treatment to be targeted towards the specific microorganism causing the infection.

Ongoing Monitoring

Because corneal infections can change rapidly, follow-up appointments are often scheduled over the following days to monitor healing and assess whether treatment should be adjusted.

How Are Corneal Infections Treated?

Treatment depends on the underlying cause and severity of the infection. Once a diagnosis has been made, your ophthalmologist will recommend a treatment plan tailored to the specific microorganism involved and the extent of corneal damage.

Medications to Control the Infection

Depending on the cause, treatment may include antibiotic, antiviral, antifungal or antiparasitic eye drops. In some cases, oral medication may also be prescribed. During treatment, patients are usually advised to stop wearing contact lenses until the infection has completely resolved.

Close follow-up appointments are often required, particularly during the early stages of treatment, so your ophthalmologist can monitor healing and adjust medication if necessary.

When Might Surgery Be Needed?

Most corneal infections respond well to medication when diagnosed and treated promptly. However, severe infections may occasionally cause significant corneal thinning, perforation or permanent scarring that affects vision.

In these situations, cornea surgery may be recommended. Depending on the extent of the damage, this may involve a corneal transplant, where damaged corneal tissue is replaced with healthy donor tissue to restore the integrity of the eye or improve vision.

Early Specialist Care Can Help Protect Your Vision

Although many cases of red eye are not serious, some require prompt specialist attention to prevent avoidable damage to the cornea. Recognising the warning signs and seeking assessment without delay can make a significant difference to both treatment outcomes and long-term vision.

At the Eye & Cornea Surgeons in Singapore, care is provided by Prof Donald Tan Tiang Hwee, Dr Chan Wing Kwong and Dr Anna Tan Wee Tien, who have extensive experience in diagnosing and treating corneal infections and other complex corneal conditions. If your symptoms are persistent or worsening, contact the clinic to arrange a specialist consultation.