Monthly Archive for: ‘August, 2012’

Acanthamoeba Keratitis

Acanthamoeba Keratitis.

Acanthamoeba Keratitis is a serious corneal infection caused by a free living parasitic protozoan (amoeba), which is commonly found in water and soil. The Center for Disease Control in the USA recently had a look at the risk factors for this serious corneal infection. Unsurprisingly contact lens wear is a significant (the biggest) risk factor, but still contact lenses ARE SAFE, as long as you follow all the guidelines.

Contact Lens hygiene is the most significant way to reduce the risk of infection, and although mostly we are concerned about bacterial corneal infections, improper lens care also increases the risk of Acanthamoeba Keratitis (AK).

Minimise your risk by following the lens care instructions properly. Even if your care solutions claim to be “No Rub”, we would always suggest a 10 second rub and rinse of the lenses- on removal a lens is covered in a biofilm- mucus, protein, bacteria, molds, cosmetics, and anything else which may have drifted into your eye during lens wear. This biofilm is a food source to acanthamoeba, so clean contact lenses mean less risk. Also, because the solutions can get straight to the lens surface, they can begin disinfection immediately, and a simple rub and rinse will reduce the bacterial contamination on the lens 100000 fold, which means there are less for the solution to deal with.

Never EVER reuse contact lens solutions- people who admitted that they “topped off” their solutions are hugely greater risk (4x) -they were just adding to the solution left over in their case from the previous days (or weeks)- there is no way to guarantee the efficacy of used solutions! Every day the solution should be discarded and the storage case left to air dry.

Other stated risk factors are people who wear lenses less than 12 hours per day, the under 26s and over 55s, and wearers who have worn lenses for less than 5 years. The CDC attempted no explanations of the findings at this time, only the statistics. This author cannot see any reason why longer contact lens wear, longer than 12 hours would reduce the risk.

Acanthamoeba is particularly a problem where water is stored in tanks before use- in some countries, modern houses have mains water to every tap, but in Ireland this would be very rare. All contact lens wearers should attempt to minimise their exposure to water when wearing lenses- shower before putting them in, don’t swim in them (or if you must, discard them afterwards and put a new pair in). Hot tubs are a particular worry, as they are at a perfect temperature to breed all kinds of bacteria which can cause eye infection and again act as a food source. Tap water may be safe to drink and wash hands, but it should not be used on lenses or their case- the case should be regularly cleaned and rinsed with the care solution paying attention especially to the threads. The CDC recommended at least 3 monthly case replacement to prevent a risk increase.

We would expect that all of the above is not news to our own contact lens patients- we believe that the risks and “do’s and dont’s” should be clearly explained to all our patients when they are fitted with lenses and taught application and removal.

If you are taking chances- if any of the risk factors above apply to you, it would be best to change your ways before problems occur!

Contact Lenses are safe if used correctly.

Back to School

A child wearing a pair of Harry Potter style spectacles

A child wearing a pair of Harry Potter style spectaclesAn estimated 1 in 4* of school age children have some sort of visual problem, yet approximately only 1 in 3* children have had an eye test prior to starting school. A recent study* found that 11.5 % of teenagers have undetected or untreated visual problems.

School screening is a worthwhile exercise, but a failure at a screening does not mean the child has a problem, and importantly, passing the screening does not mean the child doesn’t have a problem -Screenings are designed to attempt to maximise sensitivity (catch the problems) and minimise over referrals- failures (Specificity). There is a trade off in screening- the only way to ensure 100% sensitivity would be to fail every child, but that makes it useless. Errors are a fact of screening, and only a full eye examination can determine which children are OK and which are not.

All children should be tested by either their local optometrist or at the local community children’s clinic, even if there is no suspicion of a problem- many childhood visual problems can last a lifetime if not detected early enough. We would recommend a first test aged 3, but at the very latest before starting school in all children who appear to be without problems. Obviously any child with a suspected problem should be seen as soon as possible.

* References are available on request.

More information on children’s eyecare here.

Statins increase the risk of Cataract

An eye with a cataract

A recent Canadian study has reported that people prescribed Statins- drugs used to reduce cholesterol, have a 50%  increase in the likelihood of developing age related cataract. The report also found that Type II (mature onset) Diabetics (who already have an increased risk) are at an even greater risk.

Because raised cholesterol does not co-exist well with Diabetes, many (perhaps most) Diabetics are on cholesterol lowering medicines.

The increase in cataract has been explained by the crystalline lens membrane’s need for a high cholesterol  level to ensure proper cell development and therefore normal clarity.

This was a large study (about 6400 people), so the results are pretty clear, but commentators would agree that the impact of a cataract (which is fixable) on as person’s quality of life is much less, compared to a stroke or a heart attack, and many people in this age group would have likely have developed cataract anyway.

The full article can be seen here (you may be required to register and login).

Local eyecare for all the family

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