How to diagnose Acanthamoeba Keratitis

Source: Muhammad Hamza – Corneal Fellow at University Hospital Southampton NHS FT – UK

Acanthamoeba Keratitis early diagnosis is a key factor and how, is for many, a dilemma.

Acanthamoeba Keratitis, a nasty parasitic infection is one of the most dreadful infection followed by Pseudomonas which is bacterial infection. Early diagnosis is the key but the most important and significant problem is its diagnostic dilemma, which sometimes in experienced hand can be missed or may get disregard if not have taken proper history.

After seeing most Acanthamoeba cases in the last 3 years, I consider myself lucky to have picked them at an early stage of infection, therefore all my patients have achieved vision of 6/7.5 or better. I am very happy to share with you few tips / rules, as how to pick or diagnose AK at early stage or have minimum chance of missing… of course, not 100% but at least less chances of misdiagnosing it.

Rule no.1 Is History

One thing which I have come across and convinced about AK related infections is that, these do not occurs in day or two, instead the parasites actually have been cooking for at least more than 2 weeks or so, so it’s very important to ask the history of the last 1 month or even 2 months back of the patient with their contact lenses.

You should pay attention to this type of history or suspect AK if you hear light sensitivity/ blurry vision / foreign body sensation, especially more when using Contact Lenses (here after referred as CLs), and feeling for 1 or 2 months uncomfortable with CLs,

Please ask these questions:

  1. Does the affected individual, swims with CLs, shower, or even have visited any new pool in last 2 months or shared anyone’s private swimming pool?
  2. Did the person shower with CLs, if so, was it always or occasionally or somewhere else apart from home?
  3. Does the person wash their hands before putting the CLs in the eye and before taking them out of the eyes?
  4. Did the person dry their hands with dry cloth or tissue paper before touching their CLs; or they did not dry them at all?
  5. Does the person clean their CLs regularly, have you ever rinsed CLs itself?
  6. Have they touched inside their eyes while wearing CLs?

These are some of the most important questions and does not take long for a doctor to ask. Always suspect AK in CLs patients until proven otherwise

Rule no. 2 is Examination

Main thing to look for is Corneal epithelial disruption, you may not necessarily see clear epithelial defect but you can see superficial punctuate Keratitis or some Sub Epithelial lines or Ridges , or if you are lucky enough you will see clear Pseudo dendritic pattern , but remember early pattern of AK, will not stain with Fluorescein so carefully look for any suspicious pattern in Cornea.

Rule no. 3 Do an imaging OCT and Confocal microscopy

OCT (Optical Coherence Tomography), as patients are usually photophobic, examination can sometimes get difficult, please do OCT if you have the possibility or have it down at another location, by doing this, you can see epithelial changes and most importantly Radial keratoneuritis representing white ridges in Stroma or Sub epithelium.

Confocal microscopy, If you doubt and have facility to have Confocal microscopy, or can get it done from somewhere else, please do before corneal scrapes.. Personally I have picked more cases with Confocal then Corneal scrapes, although not 100% accurate but it can pick AK cysts even at early stage of disease. Corneal Scrapes and Epithelial PCR Scrape epithelium and send for PCR, Lesion should always be scraped, even if Confocal positive. Results may take up to 10 days but at least if positive, one can act accordingly,

Remember, not always but usually outcome are better if picked within 6 weeks of onset of infection.

Do not start steroid drops on the eye until you have ruled out possibility of AK (wait till AK corneal scrape result with can take 10 days or PCR that can take 3 days). 10 % of cases can be Poly microbial, so keep the patient on Antibiotics even if get positive results of AK with Confocal or Scrapes . Always act promptly with keeping a track of days of infection, CLs related infection are not easy to treat especially now with fungal infections are more and more getting diagnosed.

Always suspect of AK if corneal ulcer is not responding or is responding to conventional antibiotics slow.

In the end, I would say:

  • to the patients. Please give detailed history to your doctor to have better understanding and outcome.
  • to clinicians, please carefully look for signs and pay attention to the symptoms, if you are not trained then please refer to someone who you think may know better or have more experience in treating AK, time is of essence when diagnosing and treating AK.

How do you treat Acanthamoeba Keratitis

Regarding treatments for Acanthamoeba Keratitis, what we have experienced till now – based on a non standard protocol –  that each doctor/country does have their own protocol. It is important that the sooner you are diagnosed the better! The first weeks are very intense but vitally important to adhere to. Look for professionals with experience in Acanthamoeba Keratitis. 

Usually once AK is confirmed, you will be given drops and/or pills (depends on each doctor) and you will have to take these eye drops every hour for several days 24/7, then moving to every hour (except the night) and depending on how the treatment is working they will adjust accordingly.

Important, do not underestimate the pain and ask for painkillers if needed, each person deals with pain in a different way and it is important you get some rest throughout the first weeks.