|Classification and external resources|
An eye with non-ulcerative sterile keratitis.
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight. It may cause feelings of itchiness each time the individual blinks.
Superficial keratitis involves the superficial layers (i.e. the epithelium) of the cornea. After healing, this form of keratitis does not generally leave a scar.
Deep keratitis involves deeper layers of the cornea (i.e. The epithelium, Bowman's Membrane and often stroma), and the natural course leaves a scar upon healing that impairs vision if on or near the visual axis. This can be reduced or avoided with the use of topical corticosteroid eyedrops.
- Amoebic keratitis. Amoebic infection of the cornea is the most serious corneal infection, usually affecting contact lens wearers. It is usually caused by Acanthamoeba. On May 25, 2007, the CDC issued a health advisory due to increased risk of Acanthamoeba keratitis (AK) associated with use of Advanced Medical Optics (AMO) Complete Moisture Plus Multi-Purpose eye solution.
- Bacterial keratitis. Bacterial infection of the cornea can follow from an injury or from wearing contact lenses. The bacteria involved are Staphylococcus aureus and for contact lens wearers, Pseudomonas aeruginosa. Pseudomonas aeruginosa contains enzymes that can digest the cornea.
- Fungal keratitis (cf. Fusarium, causing recent incidences of keratitis through the possible vector of Bausch & Lomb ReNu with MoistureLoc contact lens solution)
- Viral keratitis
- Onchocercal keratitis, which follows O. volvulus infection by infected blackfly bite. These blackfly usually dwell near fast-flowing African streams, so the disease is also called "river blindness".
- Exposure keratitis — due to dryness of the cornea caused by incomplete or inadequate eye-lid closure.
- Photokeratitis — keratitis due to intense ultraviolet radiation exposure (e.g. snow blindness or welder's arc eye.)
- Ulcerative keratitis
- Contact lens acute red eye (CLARE) — a non-ulcerative sterile keratitis associated with colonization of Gram-negative bacteria on contact lenses.
- Severe allergic response may lead to corneal inflammation and ulceration (i.e. vernal keratoconjunctivitis).
- Feline eosinophilic keratitis — affecting cats and horses; possibly initiated by feline herpesvirus 1 or other viral infection.
Effective diagnosis is important in detecting this condition and subsequent treatment as keratitis is sometimes mistaken for an allergic conjunctivitis.
Treatment depends on the cause of the keratitis. Infectious keratitis can progress rapidly, and generally requires urgent antibacterial, antifungal, or antiviral therapy to eliminate the pathogen. Treatment is usually carried out by an ophthalmologist and can involve prescription eye medications, systemic medication, or even intravenous therapy. It is inadvisable to use over-the-counter eye drops as they are typically not helpful in treating infections, also using them could delay correct treatment, increasing the likelihood of sight threatening complications. In addition, contact lens wearers are typically advised to discontinue contact lens wear and replace contaminated contact lenses and contact lens cases. (Contaminated lenses and cases should not be discarded as cultures from these can be used to identify the pathogen).
Antibacterial solutions include levofloxacin, gatifloxacin, moxifloxacin, ofloxacin. Steroid containing medications should not be used for bacterial infections, as they may exacerbate the disease and lead to severe corneal ulceration and corneal perforation. These include Maxitrol (neomycin+polymyxin+dexamethasone), as well as other steroid medications. Aciclovir is the mainstay of treatment for HSV keratitis and steroids should be avoided at all costs in this condition. Application of steroids to a dendritic ulcer caused by HSV will result in rapid and significant worsening of the ulcer to form an 'amoeboid' or 'geographic' ulcer, so named because of the ulcer's map like shape.
Some infections may scar the cornea to limit vision. Others may result in perforation of the cornea, (an infection inside the eye), or even loss of the eye. With proper medical attention, infections can usually be successfully treated without long-term visual loss.
- Chronic superficial keratitis, or pannus, for the disease in dogs
- Thygeson's superficial punctate keratopathy
- Martín-Navarro, M.; Lorenzo-Morales, J.; Cabrera-Serra, G.; Rancel, F.; Coronado-Alvarez, M.; Piñero, E.; Valladares, B. (Nov 2008). "The potential pathogenicity of chlorhexidine-sensitive Acanthamoeba strains isolated from contact lens cases from asymptomatic individuals in Tenerife, Canary Islands, Spain". Journal of medical microbiology 57 (Pt 11): 1399–1404. doi:10.1099/jmm.0.2008/003459-0. ISSN 0022-2615. PMID 18927419.
- CDC Advisory
- Tang A, Marquart ME, Fratkin JD, McCormick CC, Caballero AR, Gatlin HP, O'Callaghan RJ (2009). "Properties of PASP: A Pseudomonas Protease Capable of Mediating Corneal Erosions". Invest Ophthalmol Vis Sci 50 (8): 3794–801. doi:10.1167/iovs.08-3107. PMC 2874894. PMID 19255155.
- "What is onchocerciasis?". CDC. Retrieved 2010-06-28. "transmission is most intense in remote African rural agricultural villages, located near rapidly flowing streams...(WHO) expert committee on onchocerciasis estimates the global prevalence is 17.7 million, of whom about 270,000 are blind."