Amoebic Keratitis - Symptoms, Diagnosis, and Treatment

Introduction

Amoebic keratitis, also called acanthamoeba keratitis, infects the cornea, which is a clear dome covering the colored part of the eyes. It was described in 1973 as a parasitic infection seen in contact lens wearers. Acanthamoeba is a free-living amoeba, and it is found in pools, hot tubs, tap water, shower water, sewage systems, and contact lens solution. It is caused by a tiny amoeba called acanthamoeba. It can lead to permanent vision loss or blindness. Initially, symptoms are mild, and if left unnoticed, then the situation gets worse. The infection can occur in both eyes, and it is not contagious. However, diagnosis of the disease is challenging, and available treatments are lengthy and complex against all the strains.

What Are the Risk Factors Associated With Amoebic Keratitis?

• It can occur and be seen in individuals wearing contact lenses.

• Exposure to organisms mainly through contaminated water can predispose them to this condition.

• Low tear levels of anti-acanthamoeba IgA lead to infection.

• Corneal trauma can be a risk factor.

• Improperly storing and handling lenses can lead to this condition.

• Disinfecting lenses using tap water or a homemade solution can cause amoebic keratitis.

• Swimming and the use of hot water while wearing lenses can cause this condition.

• The use of polluted water to wash eyes can also lead to the condition.

• If there is a history of damage to the cornea.

What Are the Forms of Amoebic Keratitis?

Acanthamoeba exists in two forms: trophozoites and cysts.

1. The trophozoites are mobile, consume bacteria, and help diagnose E. coli.

2. The trophozoites from double-walled cysts are resistant to methods of killing such as freezing, heating, and irradiation.

Both forms can enter the eyes and nasal mucus membrane. Amoeba is attached to the cells on the outer surface of the cornea through corneal abrasions. The penetration further moves into the cornea with the spread of infection.

What Are the Symptoms Associated With Amoebic Keratitis?

• The sensation of something (discomfort) in the eyes.

• Pain and itching in the eyes.

• Redness or inflammation in the eyes.

• The blurring of vision initially.

• Sensitivity to light is called photophobia. The patient feels afraid to go in bright lights.

• Excessive tearing of eyes.

• Cloudy cornea or cornea may look dirty.

• Whitish rings are formed on the surface of the eye.

What Are the Complications Associated With Amoebic Keratitis?

• Uveitis is defined as inflammation in the eyes. It is one of the common complications of amoebic keratitis.

• Iris atrophy is a rare progressive disorder of displaced pupils and degeneration of the iris. In severe cases, complete degeneration of the iris occurs.

• A cataract is defined as the clouding of the lens of the eyes and is seen as a complication of amoebic keratitis.

• Scleritis is inflammation of the sclera or white part of the eye.

• Glaucoma causes vision loss and blindness by damaging the optic nerve. It is seen in complicated cases of amoebic keratitis.

How to Diagnose Amoebic Keratitis?

• Examining the Eyes: Ophthalmologists can diagnose amoebic keratitis by examining the eyes. It reviews the symptoms associated with amoebic keratitis and the hygiene associated with using contact lenses.

• Stains: This diagnoses amoebic keratitis, especially for detecting cysts in fresh clinical material or lens-case solutions. Examples include lactophenol-cotton blue or Giemsa, calcofluor white, and acridine orange usually give excellent results.

• Plate Culture Technique: The plate culture technique is the gold standard in the diagnosis of amoebic keratitis.

• Corneal Scraping: It is performed in which cells are removed from the surface of the cornea with the help of a small blade or brush. Then the cells are studied under a microscope, or lab tests are performed to check for infection.

• Confocal Microscopy: It is also used to diagnose amoebic keratitis. In this examination, laser light creates detailed images of your cornea's layers.

• Biopsy: A biopsy is done if the condition worsens and helps diagnose the situation and cause.

What Is the Treatment Associated With Amoebic Keratitis?

• Topical Antiseptic: This can be used in the treatment of amoebic keratitis. Antiseptic may fight the bacteria, which is applied in the undersurface of the eyes. The duration of treatment can range from six months to one year.

• Topical Antibacterial: Topical Chlorhexidine 0.02% or Topical Polyhexamethylene biguanide 0.02% are used to treat amoebic keratitis.

• Antifungals and Antibiotics: The ophthalmologist also prescribes antibiotics or antifungal medications.

• Steroids: Steroids are given to treat the pain and inflammation associated with amoebic keratitis.

• Surgery: If the condition does not improve with the help of medicinal treatment, then surgery is carried out to treat the disease. Penetrating keratoplasty is done. In this surgery, full-thickness corneal transplantation is done. Trephine of relevant diameter is the choice to make full-thickness resection of a patient's cornea, followed by the placement of a full-thickness corneal graft. The outcome of the surgery is good for the patients.

How to Prevent Amoebic Keratitis?

• Maintaining hygiene and washing your hands before handling and wearing contact lenses helps in reducing the occurrence rate of contact lenses wearing persons.

• Rubbing and rinsing the surface of the lenses before storing them.

• Avoid rubbing the eye with contact lenses.

• Use only sterile products to clean and disinfect your lenses to maintain proper hygiene.

• Avoid tap water to store contact lenses. It may contaminate the contact lenses and can cause infection.

• Use a new solution to keep the contact lenses in the case.

• Replace lenses as per the schedule of the ophthalmologist or the consultant.

• Do not sleep with contact lenses, and never wear contact lenses while swimming.

• Never swap lenses with someone else. It could lead to infection in healthy individuals.

• Consult an ophthalmologist immediately if you experience redness, secretions, visual blurring, or pain.

Conclusion

Acanthamoeba is the most common free-living amoebae present in the environment and is considered an opportunistic (seen in individuals with lowered immunity) infection in humans. Amoebic keratitis is a severe consequence mainly caused because of wearing contact lenses. Therefore, contact lenses should be cleaned and stored according to the manufacturer's recommendations. Earlier diagnosis and treatment are associated with a better prognosis; otherwise, complications may arise, and it becomes difficult to manage the disease. Early diagnosis and accurate treatment are a must to prevent progressive damage.