Keratitis is inflammation of the cornea, and like inflammation anywhere can have multiple causes. We are going to consider only a few.
Contact Lens Associated Keratitis (CLAK) is common, but the challenge is to differentiate relatively benign immune-mediated CLAK from a bacterial keratitis which is also commoner in contact lens wearers. Fortunately, the two entities usually look quite different, and an experienced corneal sub-specialist can usually differentiate the two with a careful examination.
Bacterial keratitis is often called microbial keratitis but this is rather vague. This is a very serious condition indeed, and without prompt treatment there is a real risk of losing vision and even the eye! After sampling for laboratory investigation, intensive antibiotic treatment is required day and night, and this is usually very time-consuming and prevents normal daily activities. One particular microbe, acanthamoeba, is even more serious as it is very difficult to diagnose. In many cases, a corneal graft will be required to treat the scarring that occurs with healing but which degrades vision.
Keratoconjunctivitis sicca means inflammation of the cornea and conjunctiva due to dry eye syndrome. This can be mild, but occasionally can progress to serious corneal involvement with the potential for loss of vision. As such, cornel involvement in dry eye syndrome should always be taken seriously.
Viral keratitis depends on the virus. Two common causes are the shingles virus and herpes simplex. Varicella-Zoster Virus causes chicken-pox in children but reactivates from latency (“sleep”) in adults and causes shingles. A vaccine exists and is advised from the age of 60. If the shingles involves the eye, the keratitis can drag on for years and even decades, and treatment needs to be promptly started. Any eye involvement with shingles needs ophthalmic management as a matter of urgency. Herpes Simplex Virus is the cause of cold sores, usually around the mouth. However, if the virus comes into the eye, a serious keratitis results. If you get cold sores and develop a red eye, you need an ophthalmic examination as some eye drops (steroids) can make the disease dramatically worse. The treatment of both these types of keratitis may involve antiviral drugs and anti-inflammatories, but in many cases surgery will be required to restore vision.