Eye Health Central

What Is Acanthamoeba Keratitis

Acanthamoeba Keratitis, Causes, Prevention and Treatment

Acanthamoeba keratitis (AK) is an infection of the cornea, fortunately, it's rare, but serious, it is caused by microscopic organisms infecting the cornea of the eye

Acanthamoeba keratitis is an infection within the eye caused by the microscopic single-celled organism acanthamoeba. These amoebas are quite common and can be found almost anywhere that fresh water exists. This includes natural sources, like rivers, lakes, ponds, and even damp soil, but also other sources, like spas, swimming pools, and even the water that comes from the tap on the kitchen sink.

How Can I Avoid An Acanthamoeba Keratitis Infection?

Fortunately, AK is an incredibly rare infection, according to Moorfields Eye Hospital 85% of acanthamoeba keratitis infections occur in contact lens wearers, the biggest risk factor is exposing your contact lenses to water and not correctly cleaning and disinfecting them.

Poor hygiene and unsafe practices of contact lens use, like swimming while wearing contacts, increase the risk of acanthamoeba being transferred from any one of its many sources onto the surface of a contact lens. Once the lens is placed on the eye, the acanthamoeba not only survive, but thrive and multiply. As their numbers increase, the infection takes hold, symptoms will begin to show. Various studies have shown that this infection can arise from using tap water to soak lenses in, rather than using an approved contact lens soaking solution.

The best way to avoid acanthamoeba keratitis is to follow the advice of your contact lens practitioner and never wear contact lenses whilst, swimming, in the hot tub or, in the shower, and never clean or soak your lenses in tap water.

What Are The Symptoms Of Acanthamoeba Keratitis?

The signs of acanthamoeba keratitis aren't that dissimilar to many other types of eye infections and diseases. The eyes will likely become red, watery, and painful, especially after removing the contact lenses. 

There may also be sensitivity to light and even blurred vision, along with the sensation of a foreign body in your eye.

These signs and symptoms can often be confused with conjunctivitis.

An infection of acanthamoeba keratitis begins when the organism gets into the eye and begins secreting proteins. This secretion causes the cornea to dissolve and the amoeba begins to eat the healthy bacteria that normally live inside the eye, as well as corneal tissue. Those who suffer from this disease usually show symptoms including 

  • Acute pain,
  • Inflammation and 
  • Redness in the cornea. 
  • Circular ulceration(In severe cases,) may also be found. 

Acanthamoeba infection advanced ring infiltrate

If detected early, the infection can be treated quickly and effectively, however, if left untreated for too long, significant damage can occur to the eye, and those suffering from the illness could lose their sight.

What To Do If You Think You Have Acanthamoeba Keratitis

Remove your lenses and, seek professional medical attention as soon as possible. Let your Optometrist, doctor, or hospital know you are a contact lens wearer and your lenses may have come into contact with water.

Any delay in medical treatment will allow the acanthamoeba to multiply, worsening the infection.

How Is Acanthamoeba Keratitis Diagnosed

Under ideal laboratory situations, acanthamoeba can be detected by placing suspected samples on agar saline plates along with specific types of bacteria, such as E. coli, which will promote the reproduction and growth of the amoeba.

The culture is then viewed under a microscope, where a trained professional will be able to identify them by their blob-like, single-cellular appearance. While acanthamoeba are impossible to see with the naked eye, they are rather large in comparison to bacteria and far larger than the human cells that comprise the eye.

Acanthamoeba keratitis remains one of the more challenging clinical entities in corneal disease and most cases of acanthamoeba keratitis are diagnosed once the treatment for the first (and inaccurate) diagnosis of conjunctivitis proves to be ineffective. Usually, around the same time that it's clear that antibiotics aren't working, the infection has progressed to the point that a circular, ring shaped ulcer has begun to develop around the eye's cornea.

How Is Acanthamoeba Keratitis Treated

The treatment method used is largely dependent on how far the infection has progressed. If caught early enough, the disease can be treated with one of a number of available drugs. The most commonly prescribed medications are polyhexamethylene biguanide (PHMB), Propamidine isethionate, and chlorhexidine.

In severe cases, simply killing the acanthamoeba won't be enough, as the infection has caused serious and irreparable damage to the eye tissue. In order to restore the visual impairment caused by this damage, a keratoplasty, also known as a corneal transplant, may be necessary, which is a complete or partial removal and replacement of the eye's cornea.

The more severe the infection becomes, the more likely there will be permanent visual acuity loss. Vision may become blurry or clouded, and while partial visual restoration may occur once the infection has been eliminated, it may not return to the level of clarity that existed prior to infection.

The disease is very easy to prevent, but very difficult to treat. Even with proper medical care, there is a serious risk of severe visual impairment or blindness. In some cases, complete corneal transplants may be required, which can be complicated and challenging to recover from.

How Can Acanthamoeba Keratitis Be Prevented

The best method of prevention is to practice safe contact lens hygiene, and not take any unnecessary risks that may contaminate either the contact lenses themselves, or the eyes.
First and foremost, follow any instructions given by the contact lens practitioner at the time of fitting. Check out our helpful contact lens aftercare periodically to refresh your knowledge of best practices for contact lens wear, and care.

Only use safe and approved contact lens cleaning and storage solutions. Never use regular tap water, it's not sterile and is likely to result in an infection. Swimming, bathing, and spa usage are all best after contact lenses have been safely removed. Partaking in water-based activities while wearing contact lenses creates an opportunity for infecting bodies to find their way onto the lenses, and eventually the eye. 

  • Always wash and dry your hands before putting in or removing your contact lenses, and use a fresh cleaning and storage solution every time.
  • Never reuse or top up cleaning and soaking solutions as this can increase the risk of infections including acanthamoeba keratitis. 

Author: John Dreyer Optometrist Bsc(Hons), MCOPTOM, DipCLP
Created: 19 Feb 2024, Last modified: 20 May 2024