What is binocular vision, orthoptics and vision therapy?

Binocular vision is the vision obtained when the two eyes work properly together to provide a high quality single vision with steropsis (3-D vision). It is important that a high level of binocular vision is obtained effortlessly.

Orthoptics is the discipline of assessing how the eyes work together and the level of binocularity. An hospital orthoptist is a highly trained practitioner who specializes in this discipline. Optometrists also practise orthoptics but will refer complex cases to the ophthalmologist & orthoptist team.

Vision therapy is a term sometimes used interchangeably with orthoptics, especially by optometrists.

Behavioural optometry is considered by some as possibly a controversial method of vision therapy. This is because there is currently little evidence that the specific therapies employed as “behavioural optometry” are effective. For example some optometrists may link poor "tracking" as a cause reading underachievement despite little or no evidence. However, behavioural optometrists usually also use evidence-based orthoptic treatment for conditions such a convergence problems.

Binocular vision & binocular vision anomalies

When the two eyes and the vision of each eye are coordinating perfectly well together, this is called normal binocular vision. Your eye examination may reveal that your symptoms are caused by your eyes not working together, a binocular vision anomaly. This may be due to poor eye co-ordination and muscle strength (motor), that the vision of each eye does not syncronise fully within the brain (sensory) or a combination of both of these..

If this is the case, a more in depth examination may then required and it will be suggested a further appointment is made to carry out specialist examination, called an orthoptic (or binocular vision) assessment. Having investigated fully and diagnosed the binocular vision anomaly, a treatment and management plan will be discussed with you.

Generally, binocular vision problems are treated or managed using spectacles, prisms, orthoptic eye exercises, surgery or botulinin injections. Rarely, in the case of intractable double vision, an eye patch has to be worn or a course of hypnotherapy is recommended.

Orthoptic or binocular vision assessment

Some of the tests will have been included in your eye examination and, if your child is having a Visual Assessment, an orthoptic assessment is included.

The orthoptic assessment covers detailed tests of motor and sensory binocular vision. These tests include cover test, dissociation tests, tests for fixation disparity or associated phoria  (including Mallett and Zeiss Polatest),  voluntary and reflex ocular motility, voluntary and reflex convergence, binocularity tests to assess suppression; stereopsis, measures of fusional vergence reserves, and accommodation amplitudes, facility & lag. In the presence of squint (strabismus) other tests include investigation of sensory status – tests for harmonious abnormal retinal correspondence (HARC) suppression tests - and eccentric fixation.  


Although the practice has an infra-red eye movement recording system - Dr Barnard’s PhD research was in the field of eye movements – this is no longer used in the practice to assess “tracking” because the scientific evidence-base suggests that so-called tracking problems are not the cause of common complaints such as reading underachievement.

Treatment of the binocular vision problem or amblyopia (“lazy eye”)

This may involve changing the prescription of the spectacle lenses, orthoptic eye exercises (sometimes called vision therapy), the prescribing prisms in the spectacles or a combination of these. When indicated your optometrist advise referral to specialist ophthalmologist for further investigation, squint surgery or botulin treatment..

When the vision of one eye has failed to develop the eye has a condition called amblyopia, a so called “lazy eye”, The commonest causes for this are a previously untreated difference in prescription between the two eyes (anisometropia) or due to squint (strabismus. Strabismus and amblyopia occurs in about 3 to 4% of the population even in the developed world. This is because it is usually detected too late to successfully treat, often after a child has started school.

Dr Barnard is the inventor of a new screening device called IRISS Eye Check that quickly and effectively detects strabismus in babies and children. 

 How do I do the orthoptic eye exercises ?

Some patients are provided with a regime of exercises to carry out purely at home. Other patients need or prefer to attend the practice on a regular basis to have the exercises carried out by an optometrist specialising in this field. This will be discussed with you once we know what the problem is and the treatment strategies we will recommend. Some off the eye exercises are web based and you will be provided with a password to access them from the Barnard Levit website.

For those patients for whom it is applicable we provide in-house orthoptic exercise session using the  G-Labs computerised eye exercise