Overview

Keratoconjunctivitis is a contagious eye infection that causes inflammation on the surface of the eye. The term combines two conditions: keratitis and conjunctivitis.¹ Keratitis is the inflammation of the cornea, which is the clear, curved layer at the front of the eye that covers the iris and pupil.² Conjunctivitis refers to  irritation of the conjunctiva, which is the transparent membrane that covers the sclera (the white part of the eye).

This combined condition can lead to red eyes, itching, discomfort, blurred vision, and sensitivity to light.¹

It is often caused by bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa.^3,4 Early diagnosis and treatment are crucial to minimise further complications. Slit lamp exam, tear test and microbial cultures are some of the diagnostic tests used by doctors. Treating the condition early not only helps relieve symptoms but also helps prevent spreading the infection to others.

Clinical presentation

A patient with keratoconjunctivitis usually presents with:

• Eyes redness 
• Eyes itching 
• Watery discharge 
• Blurred vision 
• Light sensitive, called photophobia 
• Difficult opening of the eyelids, because of pain and irritation

Diagnosis

Slit-lamp test

What is a slit-lamp test?

A slit lamp test is a simple, rapid, non-invasive eye exam that uses a bright light and a special microscope to look closely at the front and inside parts of your eyes.⁵ During the test, your eye care specialist will examine different parts of your eyes, including the conjunctiva, cornea, iris, pupil, sclera, retina, and lens. Unlike some other medical tests, this one does not give results in numbers or scores. Instead, your eye specialist uses it to look for eye problems and, based on that, be able to further guide you to the appropriate treatment.⁶ 

 How is the test done? 

You will sit in a chair and rest your chin and forehead on a support to keep your head steady. The doctor will move the slit lamp—basically a strong light attached to a microscope—so it can shine into your eye. You will be asked to look in different directions while the doctor checks various parts of your eye.⁷

In some cases, your doctor might use a special dye called fluorescein. It is either placed in your eye as a drop or applied using a small piece of paper. The dye helps highlight any scratches, dry spots, or damage on the surface of the eye. A blue light is used to make the dye glow, making it easier to spot problems.⁵

A physician can detect numerous conditions using a slit lamp examination. Among other things, they may notice irregularities such as:⁶

• Cataracts (cloudiness or opacity in the lens)
• Injury or disease of the cornea
• Harm to the sclera
• A separation of the retina
• Damage to the retina or the blood vessels  
• Macular degeneration (a common cause of vision loss in older adults)
• Inflammation or disease affecting the eye's middle layer  
• Disorders impacting the optic nerve, such as glaucoma  
• Haemorrhaging within the eye
• The existence of an external object in the eye

Tear test: Doctors use tear tests to check if your eyes are making enough tears and whether your tears are staying on the surface of your eye long enough to keep it moist and healthy. Two common tests are the Schirmer test and the tear breakup time (TBUT) test.

Schirmer test

What is the schirmer test?

The Schirmer test is commonly utilised to assess the quantity of tears produced by the eyes.

How is the test done?

During the test, small paper strips are placed inside your lower eyelids. To do this, you will be asked to look upward while the examiner carefully lowers your eyelid and the folded part of the test strip into the eye. This procedure is then replicated for the opposite eye. Once both strips are inserted, you will be asked to keep your eyes gently closed, avoiding any squeezing, for a period of five minutes. After this time, you will be asked to open youreyes and look upward to facilitate the removal of the test strips.⁸ Once the strips are removed, the doctor checks how much of the paper has become wet from your tears.⁹

A score greater than 15mm is considered normal. However, a score below 5 mm signifies a tear deficiency.

Tear breakup test (TBUT)

What is the TBUT test?

This test is performed to measure the tear film stability.¹⁰

How is this test done?

This test checks how long your tears stay on the surface of your eye before they start to dry out. To do this, your doctor places a fluorescence dye into your eyes and asks you to keep your eyes open without blinking. Using a special microscope with a blue light, they watch how long it takes for dry spots to appear on your eye’s surface.

Typically, a TBUT measurement of 10-35 seconds is regarded as normal. If the value is less than 5, then it suggests your tear film is unstable and may not be protecting your eyes properly.¹⁰

Culture test

What is a culture test?

A culture test helps your doctor find out if any bacteria, viruses, or fungi in your eye could be causing an infection. This test is especially helpful if you have symptoms like redness, swelling, or discharge, and the cause is not clear.

How is the sample collected?

There are two common ways to collect a sample from the eye

1. Conjunctivitis swab

The doctor uses a soft, sterile swab (like a Q-tip) to gently wipe the inside surface of your lower eyelid, without touching the cornea (the clear part at the front of your eye). This swab is then placed in a special tube and sent to the lab. If it can not be sent right away, it is stored in a fridge to keep it fresh.¹¹

2. Corneal scraping 

If you have a more serious infection affecting the cornea, your doctor may need to gently scrape a small sample from the infected area using a fine tool. This is done very carefully to avoid touching the eyelashes or other parts of the eye. The samples are placed directly on special plates to help grow any germs that might be present .

What happens in the lab?

The samples are put on different types of growth plates (called culture media), depending on what kind of infection is suspected. Some common ones include:

• Blood agar
• Chocolate agar 
• Saboround agar
• Viral culture or PCR

What do the results mean?

• A positive culture means that a germ (like a bacteria, virus, or fungus) was found and could be causing the infection
• A negative culture means no harmful microbes were detected, but your doctor might still look at other signs to guide treatment

Conclusion

Keratoconjunctivitis is an inflammation of the outer layer of the eyeball. It includes two types of irritation: keratitis, which means the inflammation of the cornea, and conjunctivitis, which means inflammation of the conjunctiva. Early detection is necessary for the prevention of further complications. Eye care providers can easily diagnose based on symptoms like eye redness, irritation, watery discharge, and blurred vision. Test such as the slit lamp exam, tear tests, and cultures, help confirm the diagnosis and guide treatment