The eye is the most delicate exposed tissue in the body, protected mainly by the eyelids which in itself are thin skin folds. It is exposed to a range of mechanical, chemical and electromagnetic factors in the course of a day and can be easily injured or infected. The cornea is the outer transparent layer through which light passes into the eyeball. Not only does in protect the inner tissue of the eye but it also helps with bending light for clearer vision.
What is keratitis?
Keratitis is the medical term for inflammation of the cornea. It may be due to infectious or non-infectious causes. Since the cornea is the clear dome-shaped layer over the iris and pupil, it can lead to visual disturbances when inflamed apart from the redness and pain that is common in keratitis. Some cases can be very severe and even lead to loss of sight which can only be restored with a corneal transplant.
Normally the eye has mechanisms to prevent keratitis. The eyelids shut to prevent physical trauma to the cornea and the rest of the eye as far as possible. The epithelium lining the eye can also help to prevent infections in conjunction with the film of tears that coats the eye surface. However, these mechanisms can fail at times especially if the insult is too great. As a result keratitis may develop.
Causes of Keratitis
The causes of keratitis can be broadly divided as non-infectious or infectious. Differentiating between non-infectious and infectious keratitis is important because certain infectious types like bacterial keratitis need to be treated immediately. Failure to do so can lead to complications such as blindness.
Non-infectious keratitis simply means that the inflammation of the cornea is not due to an infection. It is mainly due to trauma to the cornea in these cases. Scratching of the cornea by the fingernails, airborne projectiles, prolonged use of contact lenses, torn lenses and other forms of trauma to the eye. People who work in industrial settings where there is abrasive dust in the air may also be at risk without protective eye wear.
Infectious keratitis is an infection of the cornea caused by viruses, bacteria, fungi and other parasites.
- Viral keratitis often causes acute cases that resolves spontaneously but some types like herpes simplex keratitis can be severe and lead to blindness.
- Bacterial keratitis is usually serious and progresses rapidly cause significant corneal damage within short period of time (24 to 48 hours).
- Fungal keratitis is uncommon and can persist for long periods of time. It often affects people with weakened immune systems like in HIV/AIDS.
- Acanthamoeba keratitis is also an uncommon form of infectious keratitis caused by a parasitic amoeba. It is more frequently seen in contact lens wearers.
Non-infectious and infectious keratitis can affect any person. However, those groups that are more likely to develop it include:
- People with weakened immune systems like in poorly controlled diabetes or HIV/AIDS patients.
- Contact lens users.
- Long term use of corticosteroid eye drops.
- Living in a warm climate.
- Swimming or bathing in contaminated water.
Signs and Symptoms
Keratitis does not appear significantly different from other eye conditions like conjunctivitis. The signs and symptoms of keratitis include:
- Redness of the eye.
- Eye pain and tenderness.
- Excessive tearing.
- Discharge from the eye (mucus and/or pus).
- Excessive blinking or difficulty opening the eye.
- Sensitivity to light.
- Decreased or blurred vision.
- Grittiness in the eye.
Treatment of Keratitis
The choice of treatment for keratitis depends on the underlying cause. Severe cases or delayed treatment can lead to complications which may eventually culminate in blindness. It is therefore important that keratitis is assessed by a medical professional as soon as possible and the appropriate treatment is commenced immediately. Keratitis remains one of the leading causes of blindness in all age groups.
For non-infectious causes treatment involves removing any offending agent and then using an eye patch to cover the eye. The cornea can heal very quickly if the injury is not severe or deep. In addition topical corticosteroids may be applied to the eye to reduce inflammation. The eye patch needs to be used throughout the day and night.
For infectious causes, the appropriate antimicrobial agent needs to be used like antiviral medication, antibiotics or antifungal agents. These cases need to be monitored very closely because some types like bacterial keratitis can progress very fast while other types like acanthamoeba keratitis are difficult to treat.
Complications of Keratitis
Depending on the type of keratitis, inflammation of the cornea can become chronic. With certain viral infections, like herpes simplex virus, there may be recurrent bouts of inflammation. Over time both acute and chronic inflammation can lead to ulcers forming in the cornea and even scarring. At this point the only treatment option is a surgical replacement of the cornea.
The cornea is the main structure of the eye that is responsible for bending light (refraction) which is necessary fr clear vision. The lens also bends light but to a lesser degree. Once the structure and opacity of the cornea is compromised it can affect vision to varying levels. These visual disturbances may be temporary in acute cases that are appropriately treated. However, severe and long standing cases can eventually lead to permanent blindness.
Prevention of Keratitis
As far as possible, it is best to avoid keratitis altogether and people who are considered high risk should be aware of measures that can be implemented to prevent it
- Contact lens wearers should always:
– Wash their hands before inserting and removing lenses.
– Store it in an appropriate contact lens solution.
– Regularly change lenses, especially disposable lenses, as directed.
– Ensure that the storage container is cleaned and regularly replaced.
- Industrial workers should always wear protective eye wear, not rub the eyes excessively and rinse it thoroughly with clean water in the event of any foreign body in the eye.
- Avoid swimming in water that is possibly contaminated and using protective eye wear (goggles) for frequent swimmers.
- Minimize hand contact with the eye, especially among people with weakened immune systems.
- Use artificial tears (eye drops) for dry eyes.