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Keratitis
Keratitis
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.[1]
Types
Superficial keratitis involves the superficial layers of the cornea. After healing, this form
of keratitis does not generally leave a scar.
Deep keratitis involves deeper layers of the cornea, 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.
Causes
Keratitis has multiple causes, one of which is an infection of a present or previous herpes
simplex virus secondary to an upper respiratory infection, involving cold sores.
Pathogens
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Amoebic keratitis. Amoebic infection of the cornea is the most serious corneal
infection, usually affecting contact lens wearers.[2] 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.[3]
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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.[4]
Fungal keratitis (cf. Fusarium, causing recent incidences of keratitis through the
possible vector of Bausch & Lomb ReNu with MoistureLoc contact lens solution)
Viral keratitis
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Herpes simplex keratitis (dendritic keratitis). Viral infection of the cornea is
often caused by the herpes simplex virus which frequently leaves what is
called a 'dendritic ulcer'.
Herpes zoster 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".[5]
Other
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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).[6]
Feline eosinophilic keratitis — affecting cats and horses; possibly initiated by
feline herpesvirus 1 or other viral infection.[7]
Diagnosis
Effective diagnosis is important in detecting this condition and subsequent treatment
as keratitis is sometimes mistaken for an allergic conjunctivitis.
Treatment
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 Quixinex (levofloxacin), Zymar (gatifloxacin),
Vigamox (moxifloxacin), Ocuflox (ofloxacin — available generically). 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 — available
generically), as well as other steroid medications.. One should consult an
ophthalmologist or optometrist for treatment of an eye condition.
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.