The binocular vision assessment follows either vision screening or a regular eye examination to investigate Binocular Vision Disorder (BVD) further.
Binocular vision disorder occurs due to weak eye muscles, which affect the coordination between the two eyes and the brain.
The binocular vision examination involves a series of tests to examine the two eyes’ teaming ability in all aspects, along with the visual perception and processing skills to diagnose binocular vision disorder. The best part of a binocular vision disorder is that it can be managed efficiently and effectively if diagnosed correctly.
Is binocular vision examination required even if the vision is normal, say 6/6 or 20/20?
A person with binocular vision disorder or anomaly could appear to have normal vision and may not be identified during a regular eye examination. This is because the eyes come under stress when used together, and symptoms like eyestrain or headache occur while doing visual tasks for long periods like reading, writing, working on the computer etc.
Binocular vision disorders in children
Binocular Vision Disorder (BVD) affects all age groups. It is primarily seen in school going children and young adults involved in a lot of near vision activities like using computers or desk job, as their visual system comes under a lot of strain during these activities.
Binocular vision disorder presents with multiple symptoms in children. It is often misdiagnosed and attributed to other conditions like behavioral and developmental issues that share similar symptoms.
Children with binocular vision disorders are often misdiagnosed with Attention Deficit Hyper Disorder (ADHD) or dyslexia. They show poor academic performance and are mostly branded as slow learners or weak students. Children with binocular vision disorder have visual efficiency problems and or visual processing ability.
Children with BVD due to visual efficiency have problems in one or more areas such as vision (visual acuity), using two eyes together (binocularity), focusing for long periods or for different distances (accommodation) and control of eye movements (oculomotor skills).
Due to visual processing problems, children with BVD will have difficulty at the cognition level. They will have issues with spatial skills, visual memory, visual perception and visual-auditory coordination.
It should be noted that children with BVDs may be asymptomatic as they tend to avoid all near vision activities. Parents and teachers play a vital role in observing children during the near vision activities to diagnose the condition properly so that proper treatment may be offered.
Further complicating the situation could be that regular school screening and eye examinations fail to detect BVD. A child with BVD can present with one or more of the following signs and symptoms, which manifest due to problems in visual efficiency and visual processing.
- Discomfort with reading
- Closes one eye while reading
- Avoids reading and writing as much as possible
- Feels sleepy while reading
- Lack of concentration
- Moves head while reading
- Has abnormal head posture
- Irritable and easily distracted
- Balance issues
- Watery eyes while reading
- Skips lines and words while reading
- Complains of blurred vision and words moving or floating on the page
- Reverses letters and numbers while writing
- Holds a finger against the text while reading
- Complains of headache while doing near activities
- Struggles to remember or recognize words
- Reads at a very slow pace than normal
- Poor levels of comprehension
- Poor academic performance
Binocular vision disorders in adults
Binocular vision disorders in adults are more muscular in origin than vision-related. The use of a wide variety of digital gadgets has resulted in significant demands on the visual system resulting in fatigue manifesting with multiple symptoms. The ocular discomfort increases with computer usage, and as a result, several adults land up with binocular vision disorders.
Computer vision syndrome or digital eye strain is the term used to describe eye and vision problems arising due to excessive use of digital gadgets like computers, tablets, mobile phones etc. Binocular vision disorders in adults can also occur following a muscle palsy, traumatic brain injury (TBI) or following a concussion.
People with long-standing diabetes could also be affected with eye muscle problems causing binocular vision disorders. Binocular vision disorders could also be neurological in origin. A thorough history followed by a binocular vision examination can diagnose the condition. Some of the common symptoms experienced by adults with binocular vision disorders are listed below:
- Eyestrain with near work
- Focusing difficulties
- Lack of concentration
- Sleepy all the time
- Double vision
- Pain with eye movements
Binocular vision and sports
Any sport requires high levels of visual skills, efficiency and perception, which affects the performance. An athlete’s visual efficiency in any sports could be improved by identifying the problem areas and working on its improvement.
Several exercises are recommended to improve the eye-tracking ability and work on improving the hand to eye coordination. This is so important that there is a complete branch of optometry called sports vision specialists dedicated to enhancing sportspersons’ vision.
Binocular vision examination
The following tests are part of a binocular vision examination:
History forms a significant part of the binocular vision examination. It will be an elaborate one, relevant to the patient’s age group being examined. For children, the history would cover aspects about the child’s behavior about near vision activities at home and school and any recent fall/injury, medications, family history, milestones and pre-natal history of the mother.
The history for adults would cover a range of topics, including currents complaints, hours of near work mainly related to digital gadget use, any traumatic brain injury/concussion, general health, use of medications, especially for those related to depression/anxiety, migraines, surgery etc. Adults would also be required to fill in a questionnaire as part of the history taking during binocular vision examination.
Age-appropriate vision tests would be carried to determine the patient’s status of vision. Any decrease in vision during the test will undergo thorough refraction to determine the eye’s refractive status. All those not requiring refraction (eye testing for eyeglass power) will undergo another battery of tests for the binocular vision examination.
Thorough refraction could reveal any uncorrected refractive errors if present. Children and young adults would additionally require cycloplegic refraction (eye drops used to stop eye muscles to change focus or accommodate), especially when they have mild to moderate hyperopia or amblyopia (lazy eye) or squint.
Tests to determine the binocular status of the eye
Several tests are carried out at various distances to determine the eye teaming and focusing ability in the patient; this includes
- Depth perception (stereopsis tests)
- Tests to determine any misalignment of the eye (cover tests)
- Tests to determine the focusing ability of the eyes for different distances (accommodation tests)
- Tests for converging and diverging ability of the eye (vergence tests)
- Tests for double vision (diplopia tests)
- Eye-tracking ability (oculomotor tests)
- Tests for visual perception (spatial awareness tests)
- Tests for visual processing
- Tests for visual speed
- Tests for visual memory
The tests are conducted using a series of lenses, prisms and even red-blue glasses in front of the patient’s eyes. A diagnostic test is done for patients in front of a computer with special software to detect and diagnose binocular vision disorders.
The eyes’ health is finally examined to rule out any pathology by checking for the optic nerve functioning, retinal health, pupillary functioning etc.
Whom should one visit for a binocular vision examination?
An eye care practitioner with good knowledge in vision therapy is ideal for examination. Ideally, optometrists are well trained in binocular vision, and some gain additional qualification such as a fellowship in this field. They are also known as vision therapists.
With the increasing popularity of vision therapy for managing binocular vision disorders, most eye hospitals and clinics have a separate vision therapy department. It’s a good idea to check with the nearest eye center for the availability of such services.
Treatment for binocular vision disorders
The treatment for a patient with BVD is customized and based on the individual’s binocular vision status, determined during the examination. The treatment plan in the vast majority of the cases is vision therapy.
Vision therapy is the term used for exercises for treating binocular vision disorders. Vision therapy can be offered as home exercises and as in-office therapy. In-office therapy is computer-based or where patient wears special glasses, lenses or prisms during the training on various gadgets.
Other treatment options in addition to vision therapy include prescribing glasses, contact lenses, glasses with prismatic correction and even eye drops in few cases when any eye muscular spasm is detected.
Common binocular vision disorders
This condition is sometimes called ‘lazy eye’ wherein one or both eyes do not have normal vision (6/6 or 20/20) even with best correction without any underlying disease. This condition occurs because the eye and the brain do not work together due to visual development issues. A thorough binocular vision examination needs to be done to rule out other poor vision causes.
This is one of the commonest among binocular vision disorders. The most commonly missed condition, too, as vision remains normal. Convergence insufficiency occurs due to a lack of teamwork between the two eyes during near work.
Children and young adults are more prone to this condition due to excessive near work demands. Convergence insufficiency is also the easiest treated conditions, and vision therapy offers promising results for this condition in all age groups.
It is commonly referred to as squint or eye turn or crossed eyes due to misalignment of muscles between the two eyes. There are two types of squint, namely latent squint and manifest squint.
A manifest squint is noticeable and appears as an eye turn to the observer. In contrast, the latent squint is diagnosed only during the eye examination. Latent squint can lead to multiple binocular vision disorders and requires vision therapy after careful examination.
Several other binocular vision disorders can be detected during a binocular vision assessment. The key to success in binocular vision disorder treatment is correct diagnosis and therapy at the earliest for any age group.