THOUSANDS of Scots are being exposed to the risk of CJD infection through a simple eye test that was identified as potentially dangerous four years ago.
Eye patients can contract the human form of mad cow disease as a result of a common test used to measure pressure within the eyeball, according to new research.
A machine called a tonometer, which is used to check tens of thousands of Scots annua
lly for conditions such as glaucoma, makes direct contact with the eyeball. Scientists have found it is possible for CJD-contaminated cells to be passed from one patient to another, even after the device has been cleaned.
Patients groups reacted with anger and concern to the research and said it was even more scandalous because government experts on CJD advised hospitals to discontinue use of the machine where possible in 1999.
Although disposable parts can be bought for the instruments, hospitals tend to use reusable equipment because it is cheaper and more accurate.
In the latest issue of the British Journal of Ophthalmology, researchers say they have evidence that cells from the cornea stay on tonometers even after the standard method of cleaning, which involves washing and wiping. The researchers believe it is possible, in theory, for corneal cells from a person infected with CJD to contain the prion protein that causes the disease. The researchers concluded in the that the transfer of cells "may represent potential prion infectivity".
The research team included Professor James Ironside, director of the national CJD surveillance unit in Edinburgh, and consultant eye surgeon Bal Dhillon, of Edinburgh’s Princess Alexandra Eye Pavilion.
Their report states that despite the fact that the equipment involved is cleaned before being used on the next patient, "no current cleaning and disinfection strategy is fully effective".
One problem is that equipment used many times develops tiny bumps and cracks, which can trap tiny objects such as cells. It points out that although it is unclear how infective corneal tissue may be, similar cells in animals have been found to be "highly infectious" in terms of transmitting brain disease similar to CJD.
In the absence of a foolproof decontamination system, the researchers say carefully cleaning the equipment by hand "is the single most important step in reducing the CJD risk".
Dhillon said last night: "Most units [in Scotland] are using re-usable instruments [for tonometry]. Although there are disposable ones they are not quite as good at measuring pressure for people who might have glaucoma. Everyone’s concerned about cross-infection: it’s very important not just for vCJD but for viruses as well.
"But with all interventions there is a risk-benefit attached. You have to weigh up the consequences of having glaucoma, and not following that up with the best possible measurements, against the small theoretical risk of transmission of cells [from patient to patient]."
The research recommends that hospital staff are educated in risk factors for CJD, and that careful cleaning of equipment, followed by disinfection, was vital to minimise the number of eye cells which could be transferred to another patient.
The Princess Alexandra, one of four specialist eye units in Scotland, said about 80,000 outpatients and inpatients were likely to have a contact tonometry check there each year and that many of those procedures involved the reusable form of the equipment.
Similar numbers pass through the eye units at Glasgow’s Gartnavel Hospital, Aberdeen Royal Infirmary and Ninewells Hospital in Dundee.
Margaret Davidson, chief executive of the Scotland Patients’ Association, said: "They must stop using this equipment if there is the slightest chance of getting CJD. Either a cleaning process where everything is eliminated must be found or better disposable equipment must be developed. People going for a glaucoma test cannot be put at risk."
David Wright, chief executive of the International Glaucoma Association (UK), said: "It goes without saying that we would look for the safest effective way of managing glaucoma and we would like to see disposable instruments used if that is the safest method."
Tory health spokesman David Davidson, who has a yearly tonometer check because he is diabetic, said: "I’ve never given this a second thought before. But if there is a suggestion at all that there is a major risk we need to have research done immediately to work out exactly what that risk is. The other side to this is the question can science not produce disposable equipment which is of high enough quality to eliminate this problem? That should be looked at as a matter of urgency."
Aberdeen Royal Infirmary confirmed it used the tonometers involved but said they carried an "unproven and minimal risk" of CJD which was outweighed by the benefits to people with eye disease.
Ninewells Hospital said it was "aware" of the research and was "looking into the use" of disposable parts. It said eight out of 10 of its patients are checked with a different instrument, which is guaranteed sterile.
A spokeswoman for Gartnavel Hospital said tonometers were disinfected between each patient, and that it was "not aware" of any advice about disposable instruments.
A spokeswoman for the Scottish Executive said the advice given four years ago was that optical instruments should be disposable "wherever practicable and where this does not compromise outcome".
