Easy and natural stereopsis vision assessment

Why test for Stereovision?

Why Test for Stereovision?

Simple and Indicative
  • It is easy to test for stereopsis and it makes sense to do so as the function of Binoculor Single Vision (BSV) is stereoscopic vision. Hence it is to be preferred to indirect tests of BSV, such as fixation disparity.
  • BSV is an indication of no strabismus, at least some of the time. If a patient has BSV then its benefits are a good incentive to keep the eyes straight where possible. If a patient lacks BSV then there is potentially a case for referral, particularly if the patient reports headaches, blurred vision, etc.
  • BSV can be a clinical objective. If the eyes are not straight then the clinical aim for orthoptists and ophthalmologists might be to establish BSV if the patient has the potential for achieving it. Hence BSV can be a marker for success.
Parent reassurance

Parents sometimes ask “Could my child’s clumsiness be a visual problem?” If BSV is present then the reply can be: Probably not. Some parents also ask similar questions about sports, and again the presence of BSV allows reassurance, always of course subject to overall clinical judgement taking all patient data into account.

Why do some Optometrists not test for stereopsis routinely?

Perhaps one reason is that some optometrists have used stereogram tests requiring red/green or polaroid glasses. For some children wearing these can constitute a difficulty, and hence a problem for the practitioner who can be faced with an upset child and poor results. Such episodes can be distressing for all concerned and time-consuming to resolve. A better answer to this problem is not to give up testing for stereopsis but to give up using stereogram stereotests requiring glasses. This can readily be achieved by using the Frisby Stereotests.

All Frisby Stereotests present ‘real depth’ objects viewed with natural vision

That is, they do not use stereograms to create depth effects. This avoids the disadvantages that stereograms have for some patient groups, such as young children who refuse to wear them.  Some orthoptists believe that such spectacles can be dissociating and give misleading results if the patient has fragile BSV.