What is Keratitis?
Keratitis is an infection of the cornea - the thin, clear covering at the front of the eye, causing irritation and pain.
Keratitis can be divided into two main categories Fungal Keratitis and Bacterial Keratitis and these can be further subdivided into infectious Keratitis and Non-infectious Keratitis
Fungal Keratitis, sometimes referred to as keratomycosis, is an eye infection caused by a fungus that results in an inflammation of the eye's cornea, - the thin, clear covering at the front of the eye.
Fungal Keratitis and Bacterial Keratitis have very similar presenting symptoms making it difficult to differentiate in the early stages, when seeking medical advice for possible Keratitis it is important to give your Optometrist, GP or Ophthalmologist a full and detailed explanation of events leading up to the infection.
What Are the Symptoms of Fungal Keratitis?
Fungal keratitis symptoms include blurry vision, redness, sensitivity to light, excessive tearing or discharge,
- Blurred Vision
- Photophobia (Sensitivity to light)
- Excessive tearing
- Discharge from the eye
Antibiotics will have no effect and if you are a contact lens wearer they will persist even after removing your lenses.
While similar to bacterial keratitis, the symptoms are typically much less severe. You should always get eye infections checked by an eye care professional as there may also be
- Ulcers in the surrounding tissue, such as the eyelid and conjunctiva.
In very rare cases the infection may spread to the rear of the eye, which can cause endophthalmitis, and total loss of the eye.
What Causes Fungal Keratitis?
There are five types of fungi that can lead to fungal keratitis.
- Filamentous fungi
- Aspergillus flavus
- Aspergillus fumigatus
The means by which these fungi infect the eye is usually through contact with plants, dirt, or some other type of organic matter. A thorn injury, for example, could both penetrate the surface of the eye, as well as transfer the fungi from the plant onto the cornea, where it then begins to grow and multiply. Symptoms will begin to present several days later. Another common cause of fungal keratitis is improper cleaning of contact lenses.
How is Fungal Keratitis Diagnosed?
An Ophthalmologist or Optometrist will assess the visible symptoms, and discuss recent events with the patient. Fungal keratitis can fairly easily be mistaken for bacterial keratitis, so it's common for a corneal culture to be taken, this is a quick simple procedure whereby a few corneal cells are taken by a small swab and sent for analysis to enable an accurate diagnosis.
How is Fungal Keratitis Treated?
Medicated eye drops are the likely course of treatment. Filamentous fungi are treated with natamycin ophthalmic solution, while candida yeast is treated with fluconazole ophthalmic solution. In situations where the infection does not respond to the appropriate medication, a third option is available, amphotericin B, but it can be quite toxic on its own and is only used when absolutely necessary. The time needed for a full recovery can be as little as a few weeks, or can take several months in some cases.
What is Bacterial Keratitis?
Bacterial keratitis is much more common than Fungal keratitis, this is why fungal Keratitis can often be treated for Bacterial in the first option. Bacterial Keratitis is one of the most important causes of corneal opacifications, which is the second most common cause of legal blindness worldwide after cataracts
What are the symptoms of Bacterial Keratitis?
Bacterial keratitis usually comes on rapidly and you can experience:
- Decreased vision
Any eye disorders causing, pain, redness and an altering of your vision should be checked out by an eye professional immediately
Causes of Bacterial Keratitis
Bacterial keratitis as you would expect is caused by a bacterial infection, according to the Centre for Disease Control (CDC) the most common types of bacteria are Pseudomonas aeruginosa and Staphylococcus aureus. There are many ways that these bacteria can enter the eyes and lead to bacterial Keratitis including the following
- Recent eye injury
- Eye disease
- Weakened immune system
- Infections of the eyelids
- Problems with tears
- Contact lens wear
Normal contact lens wear should not result in bacterial keratitis however poor contact lens practice or poor hygiene can lead to eye infections including
- Sleeping in contact lenses overnight - unless wearing continuous wear lenses
- Not disinfecting monthly lenses daily
- Not cleaning contact lens cases regularly
- Storing or rinsing contact lenses in tap water
- Topping up lens solution
- Sharing contact lenses
If you are a contact lens wearer and notice any eye pain, redness, decreased vision, photophobia etc, then remove your lenses and seek advice from your Optometrist or GP.
How is Bacterial Keratitis Treated?
The most common treatment for bacterial keratitis is a cause of antibiotics, which are normally in the form of a cream or eye drops, you should see improvement in symptoms within 48 hours and significant improvement within a week, if you see no change in your condition, you should return to you eye care professional as they may need to check for fungal Keratitis.
The differences Between Fungal and Bacterial Keratitis
|Symptoms||Fungal Keratitis||Bacterial Keratitis|
|Interference with Vision||✔️||✔️|
|Excessive discharge from eye||✔️||❌|
|Reacts well to Antibiotics||❌||✔️|
This table should not be used as a diagnostic tool and should not replace the advice of a qualified eye care professional.
Is Keratitis Infectious?
Whether your Keratitis is infectious or not will depend on what type of keratitis you have, this will need to be determined by an optometrist, and Ophthalmologist or a GP following a history of symptoms and causes and possibly tests.
Causes of Non-infectious keratitis include
- Dry eyes
- Foreign object in the eye
- Injury to the eye
- Snow blindness
- Vitamin A deficiency
- Sleeping in or overwearing contact lenses
Causes of infectious Keratitis
- Bacterial Infection - possibly from unclean contact lens cases
- Fungal infection - often introduced by an injury to the eye
- Viral infection - normally due to other infections such as Herpes simplex or zoster
- Parasitic infection - normally parasites found in rivers or lakes
Any infection or eye injury should always be checked out by an eye care professional.
Image credit: Eddie314, Wikipedia CC-BY-SA-3.0 via
Author: John Dreyer Optometrist Bsc(Hons), MCOPTOM, DipCLP
Created: 5 May 2016, Last modified: 3 Jan 2023