Binocular assessment

The assessment of binocular function is often one of the weaker areas of a routine, if observation of candidates in the PQE is any guide.Tests are done for no clearly logical reason, often because they always have been, and in an order that defeats the object of the testing. Binocular vision seems to be one of those areas that practitioners shy away from, and students often take an instant dislike to. Many retests and subsequent remakes of spectacles are the result of a practitioner overlooking the effects of a change of prescription on the binocular status of the patient.It would be useful to define what it is we are trying to find out:

• Does the patient have a squint or a phoria?
• If they have a phoria, is it compensated?
• If they have a binocular problem, is it going to need referral or management?

 Tests of motor function can be divided into those “binocular” tests that maintain fusion (e.g. fixation disparity) and those that dissociate the eyes (e.g. cover test, Maddox rod). As a general principle, binocular tests should always precede dissociation tests.In practice, this is often reversed and frequently patients are tested for fixation disparity having been thoroughly dissociated before, and in some cases during, the test.The odd false-positive
might be expected in these cases.