Microbial keratitis

Microbial Keratitis is an infection on the cornea – the clear window on the front of the eye. It is often related to contact lens wear or, less commonly, due to a scratch on the surface of the eye or a pre-existing eye condition.

Microbial keratitis infection is more likely with incorrect contact lens cleaning or storage, incorrect use of disposable lenses or wearing lenses overnight. Microbial keratitis can be a serious condition if not treated and can sometimes affect your vision and may leave a scar, even with the correct treatment.

What are the symptoms of Microbial Keratitis?

Microbial Keratitis causes a painful red eye and sometimes blurred vision. At first, it feels as though there is something in your eye. Your eye becomes increasingly painful due to the development of an ulcer on the surface of the cornea. Sometimes, you can see this ulcer, which looks like a small white spot on the cornea over the coloured part of your eye.

What tests are required?

In some cases, after using local anaesthetic drops to numb your eye, we take a sample from the corneal ulcer to allow us to find out which bacteria are causing the infection and plan appropriate treatment. Results can sometimes take several days to come back depending on the bacteria we are testing for.

What is the treatment?

Antibiotic drops are usually used. You are likely to need to put the drops in very frequently in the first instance.

This can be up to every hour and sometimes you will need to continue through the night if the infection is severe. The frequency of the drops is then reduced once the ulcer is seen to be reducing in size. Sometimes, your antibiotics may be changed if there is no sign of improvement after several days, or if the corneal sample results show another drop would be more appropriate. It is very important that you put your drops in regularly as these types of infections can get much worse if not treated properly.

Please do not wear contact lenses while the infection is present and for a few weeks after the infection clears, as this can lead to a serious deterioration in your condition. After the infection is fully recovered, please return to your contact lens practitioner to check your contact lens fit and use.

Further check-ups

In some cases, you will be asked to return in a few days to see if the infection is improving with the treatment. However, if the infection is mild, then you may be asked to return only if your symptoms get worse.

When to seek advice

If your eyesight becomes more blurred, if your eye becomes more red or painful rather than improving, or if you can see a white spot getting bigger on the cornea you should telephone Moorfields Eye Hospital Direct for advice attend your local A&E department. 

video transcript

Before putting in your eyedrops, first check that the drops are still in date.

If you were using a new bottle of eyedrops also check that the seal is not broken make sure you're putting the correct drops into the correct eye.

Let the correct time to instill your drops. Place a clean tissue on a flat surface wash your hands thoroughly with soap and water invert the bottle two or three times to ensure the contents are evenly mixed together.

Remove the lid and place it on the tissue tilt your head back, pull down your lower lid and form a small pocket. Make sure that the tip of the bottle does not come into contact with your skin or eyelashes as it might contaminate the drops.

Look up and gently squeeze the bottle so that a single drop falls into the pocket made by your lower lid.

Blink the drops in press lightly on the inner corner of your eye this enables more of the drop to be absorbed and not run away down your tear duct.

Wipe any excess fluid from your closed eyelids with a clean tissue.

Recap your drop bottle if you have more than one drop to instill. Wait at least 5 minutes before putting in another drop.

Wash your hands with soap and water to remove any traces of medication.

If you have any problems please contact our nurse led helpline service Moorfields Direct on 0207 566 2345

Review date: June 2026