In the last newsletter published by the College of Optometrists there is an article relating to evidence-based practice. As a practicing optometrist I agree with the sentiments that it is essential to use evidence-based methods when both assessing a patient and discussing their symptoms and my findings.

However, this immediately brings to the surface a question I am asked time and time again by patients that, to date I cannot find any reasonable evidence on which to base a coherent evidence-based response. That question is, why is two years cited as the normal time interval between sight tests? So many people, especially those between 60 and 70 years of age request a sight test at a more frequent interval, normally one year. Of course there is no reason why they cannot have a sight test every year if they choose to but if they make that choice they then remove themselves completely from the NHS system as the NHS will only pay for a test for them if it has been two years or more since their last sight test. As we all know this makes a complete mockery of the Department of Health’s assertion that NHS services are free at the point of need but that situation is for another day.

When I am confronted by a patient wanting to know why they are being denied an NHS sight test invariably the first question I am asked is who has decided it should be two years between tests and for what reasons? I have tried to find any clinical evidence that shows any coherent reasoning for this time interval but to date all I seem to come up with is that it seems like a good idea. The NHS website states ‘it’s recommended that most people should get their eyes tested every two years’. The College of Optometrists does not seem to specifically comment on sight test intervals and if they do I couldn’t find the comment even using their search engine. Specsavers, on their Ask The Expert page state, ‘for most people, it’s advisable to have an eye test every two years’. FODO seem to direct people to the official NHS documents while the Optical Confederation state, ‘while it is generally recommended that healthy adults have a sight test every two years, the regulations require that you should only carry out a GOS sight test, if you think it clinically necessary’.

The problem with all of these bits of advice is that nowhere is there any clinical evidence whatsoever that two years is the right interval for a sight test in an otherwise healthy person. I have heard a number of comments over the years along the lines of the only reason I am recalling them is to try and sell them something new, like new sunglasses, etc, or why should I pay for a sight test if there is nothing wrong? These are actually quite reasonable questions if we have no evidence.

Of a potentially more problematic nature is the contact lens wearer who the GOC say must have a sight test before I can carry out a contact lens after care if it has been over two years since their last sight test. If the person feels they have nothing wrong with their eyes and they do not want a sight test where does that leave me? I have to force them to have a test if they want to get new contact lenses in order to comply with the GOC regulations and yet if I then find nothing has changed I would find it difficult to argue with a patient who refuses to pay for the test as ‘they didn’t want it or feel they needed it in the first place’. To be frank the only reason I performed the test was to comply with GOC requirements with absolutely no clinical evidence behind why I carried out the test. I have to say I would sympathise with a patient at that point. Worse still such a position may well mean the patient may never return for a test and just access their lenses online through a rogue supplier who, evidence would show, will not be prosecuted by the GOC for supplying the lenses illegally. (Now there we do have evidence.)

It is all well and good to point out the importance of using evidence-based medicine and evidence-based scenarios when dealing with our patients but if we are going to be driven that way by our professional bodies, and may I say I do believe it is the right way to proceed, then maybe the time has come for those same institutions to rectify one of the longest running defects in our evidence base. That way we will at last have an answer to the question that our patients ask, ‘who decided that two years was the right interval for a sight test?’ I think we would all agree that evidence should be a vital base for what we do so now can we please have that most basic piece of evidence?