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Corneal Infections - Signs, Symptoms, and Treatments

Corneal infections Almost any organism can invade the corneal stroma if the normal corneal defense mechanisms, i.e., lids, tear film and corneal epithelium are compromised. Therefore, based on the causative organism, corneal infections can be mainly divided into the following types:

Types of corneal infection
On the basis of the causative agent, corneal infection can be of the following types:

Bacterial corneal infection (bacterial / Suppurative keratitis)
This is the most common type of corneal infection and is caused by a variety of bacteria with "pseudomonas" being the commonest.

Fungal corneal infection
Fungal keratitis is a serious and painful corneal disease caused by a fungal organism. Statistics show that as much as 44% of all central corneal ulcers are caused by fungi.

Parasitic corneal infection
Various organisms producing keratitis include Acanthamoeba (most common), Microsporidia, Onchocerca, Leishmania Trypanosoma bruci and Echinococcus granulosus. Acanthamoeba keratitis is a serious eye infection that most commonly occurs in individuals who wear contact lenses.

Viral corneal infection
A corneal infection caused by virus can be of the following types (s):

Herpes Keratitis: The type 1 herpes simplex virus causes herpes keratitis, which is a viral corneal infection and the most common form of eye herpes. Herpes keratitis generally affects only the top layer of the cornea and usually heals with no scarring.

Stromal Keratitis: The type 1 herpes simplex virus also causes stromal keratitis, a rare infection that goes deep into the layers of the cornea. Stromal keratitis can cause scarring, loss of vision and blindness.

Similarities of corneal infections
Corneal infections can be caused by bacteria, fungi, parasites or viruses. However, at times, there are certain common causes of infection such as severe dry eyes, an abrasion, and a foreign object in the eye, severe allergies and an inflammatory disorder. As for similarities in treatment, Cycloplegic agents such as atropine sulphate 1%, homatropine 1% or cyclopentolate 1% instilled three times a day reduce ciliary spasm and produce mydriasis, thereby relieving pain and preventing synechiae formation, irrespective of the infection type. Anti-glaucomaagents are used when intraocular pressure is high. If required, oral analgesics for pain may be used.

Symptoms of corneal infections
Common or similar symptoms of a corneal infection (regardless of its type) may include eye pain, redness, burning, itching, watery eyes, discharge, sensitivity to light, a white patch on the cornea and impaired vision.

Differences among corneal infections
Corneal infections can be well-distinguished from each other on the basis of the following criteria:

  • Causative agent (bacterial, vitral, fungal or parasitic)
  • Certain specific symptoms
  • Mode / type of treatment (antibacterial, anti-viral, anti-fungal etc..,)
There are also other differences in terms of severity and complications. For example, herpes simplex virus infection is an important cause of corneal scarring and visual impairment.

How are corneal infections diagnosed?
Although clinical signs may be insufficient to confirm infection, a break in the continuity of the epithelium associated with underlying stromal infiltrate should be considered infectious. For further confirmation, depending on the type, your doctor can diagnose your corneal infection by running tests such as a visual acuity test, a tear test, a refraction test, a slit-lamp exam and by measuring and examining the cornea. Your doctor may also run blood tests to check for an underlying disorder.

How are corneal infections treated?
Corneal infections are often treated with antibiotics. Depending on the specific type of infection, your doctor may also prescribe anti-viral or anti-fungal eye drops, as well as corticosteroid eye drops. In rare cases, if the damage is severe, you may need a corneal transplant. Almost all types of bacterial corneal infections are sensitive to broad spectrum antibiotics.

Treatment of bacterial keratitis
The antibiotics consist of an empirical therapy (based on previous clinical experience) with one or more commercially available broad spectrum antimicrobial agents. Treatment with a commercially available antibiotic that has a broad spectrum of activity against gram-negative and gram-positive organisms, such as ciprofloxacin or ofloxacin, seems to be the least expensive first approach.

Treatment for viral keratitis
As for "viral" corneal infection such as herpes", early treatment of herpes keratitis can be effective in stopping the spread of the virus deeper into the cornea. Antiviral eye drops or oral pills are prescribed by an eye doctor. It must be, however, remembered that there is no cure for ocular herpes. It may resolve on its own after few days.

Treatment for fungal keratitis
Initial treatment in fungal keratitis is usually started with natamycin (5%)

Treatment for parasitic keratitis
For Acanthamoeba keratitis, treatment is usually started with polyhexamethylene biguanide (PHMB) 0.02% or chlorhexidine 0.02%.

What happens if I let it heal on its own?
Almost all of the corneal infection will require prompt treatment for the full recommended course (duration). It is, therefore, essential to consult your doctor as soon as you notice any significant symptoms. If left untreated, any corneal infection may lead to serious complications including complete vision loss (blindness).

Are there any treatment risks? As is the case with all other medical treatments, medicines (especially antibiotics) used to treat various types of corneal infections can cause a number of side effects, depending on the type of antibiotic or medicine used. Similarly, prolong and unnecessary use of antibiotics or self-medication can also lead to drug resistance and a high risk of recurring infections.

Possible complications

  • Bacterial corneal infection: Because of its high incidence and potential complications, bacterial keratitis, is one of the most visually threatening ocular infectious pathologies. Elderly patients, in particular, tend to present with severe, central corneal ulcers with a significant risk of having a poor visual outcome Viral corneal infection: The leading cause of corneal blindness in the United States is ocular herpes. Other complications include corneal scarring and ulceration.
  • Fungal corneal infection: Fungal keratitis is a major blinding eye disease especially in Asia. If left, it may lead to the development of corneal ulcers.
  • Parasitic keratitis: As the condition progresses, a ring-shaped ulceration may be visible around the cornea. In most cases, some vision may be lost. The only way to restore lost vision is with a corneal transplant.

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