The College of Optometrists

If no phoria is found on cover test, and there are no symptoms, do you still have to do fixation disparity in the routine?

- if you think you need to.

But, in the exam I think it is best to do it, on everyone. After all - it does not take a moment and you don't know what it may show. DO IT for the exams. Besides, there is plenty of evidence that says you may get a FD unexpectedly. Look in Pickwell Bin V.

The answer to this question lies in the accuracy of the cover test.

The cover test (unless it is a subjective cover test where you ask the patient if they see the image move) simply is not accurate enough to pick up small phorias (eg 2 prism dioptre vertical phoria) which may be significant to the patient.

The ideal is to do FD plus cover test, distance and near, with the final Rx. Remember that all tests are not always appropriate on all patients - there is no point in doing FD (depending on the chart being used), for example, on a patient where VAs in either eye are less than, say, 6/18 as they may not see the markers.

The other thing to remember in the routine exam is that you will not see the patient's glasses. So the patient may be asymptomatic because of prisms in their own glasses that you will be unaware of!

The simple answer is no, if you are happy with your cover test result and the patient has no symptoms all you are doing is gathering additional baseline data. However if you have the time it would certainly do no harm in an exam setting to demonstrate that skill.

Sorry but I would have to agree with jeremyriches.

The candidate must have a good reason for doing a test in this exam and I would not advocate the use of any test to merely 'demonstrate the skill'. The test must be 'indicated.'

What is important to remember is that small vertical phorias are not easily picked up and these are the ones which tend to have most symptoms. One of the major reasons for newly qualifieds to have non-tolerances bouncing back in practice is due to removing a prism which was correcting a vetical phoria.

The patient may indeed have no symtoms in the exam but as jeremy points out, we dont have their glasses to focimiter to find out whether the reason that they dont have symptoms is due to the fact that they already had a small primatic correction in the spectacles. (However, if you ask the patient if they have prism in their specs then they may actually know as they may have had to pay extra for it).

You could argue both ways here untill the cows come home, but due to these reasons, I would expect to see it done. However, I am unlikely to fail a candidate unless they have missed something that is glaringly obvious. What I am not comfortable with is candidates who do tests for the sake of them.

I agree with Jane that in the real world you should not do a test unless it was indicated, however the exams are not the real world they are an artificial environment where you are demonstrating your ability to conduct a routine (much like the artificial environment of a driving test) to an examiner's satisfaction. I think a lot of examiners would expect you to do fixation disparity (see above) as part of that routine and it would be sensible to do it.

I would however suggest that in that case you incorporate fixation disparity into your eye examinations in practice so it really is routine, it is never a good idea to do a test that you have not done very often or even for the first time since leaving University in an exam setting.

Just to repeat myself again - you stand a chance to fail if you don't do FD testing. It is good practice and routine and it doesnot take a second. Thanks for agreeing with me Jane.