Balance and Dizziness: The Visual Connection
It’s not just about your vision – it’s about how your eyes work together!
Summary of a talk given by Sandy Johal, BSc, OD, FAAO, FCOVD, at St. Paul’s Hospital on May 18, 2016. Dr. Johal is a Board Certified Developmental Optometrist. She is currently the president of the Canadian Chapter of the College of Optometrists in Vision Development and practices at Panorama Optometry in Surrey, BC.
Developmental optometrists are highly specialized doctors of optometry who have completed advanced studies in vision care. Also known as behavioural optometrists, they look beyond the eyeball to determine how well your complete vision system is functioning. Their goal for dizzy patients is to improve their quality of life and help them return to work and other activities.
Examination by a developmental optometrist
A regular eye exam takes about 20 to 30 minutes to determine if you need a pair of glasses. Extensive testing of every area of the visual processing system, however, takes much longer and is usually done over three appointments.
The first exam takes about 40 to 60 minutes and includes the following:
- evaluating your visual system;
- taking a look at your eyeglass prescription;
- measuring how your eyes coordinate, both at a distance and close up;
- checking to see if you need any prism in your glasses;
- finding out how well your eyes are focusing; and
- looking to see if any tint is necessary in your glasses to help with dizziness or light sensitivity.
This first exam may need to be broken into two or three visits for very dizzy patients.
The second exam looks at the health of your eyes and takes about 20 to 30 minutes. It investigates whether or not any of your double vision or dizziness issues are related to eye health. The doctor will look at the front surface, lens and cornea and then dilate the eye to get a good picture of the retina.
It is important to arrange for someone to drive you home after the first two appointments. The first exam can make dizzy patients really dizzy. Your vision will be blurry for several hours after the second exam making it unsafe to drive.
The third exam maps out the visual field. Many measurements are taken to evaluate your central and peripheral (side) vision.
What do these tests look for?
The most common visual issue that causes dizziness is not the clarity of your vision but how your eyes are functioning. Developmental optometrists test to see how the eyes are:
- tracking – your eyes need to be able to track objects when you go for a walk or words on a page when you read;
- teaming (coordinating); and
- focusing – after a concussion or some other event focusing is often completely destroyed.
Post Trauma Vision Syndrome (PTVS)
Vision problems after traumatic brain injury are referred to as Post Trauma Vision Syndrome (PTVS). Common visual pathological conditions of PTVS include:
- oculomotor dysfunction (eye tracking);
- binocular dysfunction (eye teaming); and
- accommodative dysfunctions (eye focusing).
Common symptoms of PTVS are:
- blurred vision;
- double vision;
- difficulty reading or using a computer;
- visual movement – a sensation that your world is moving;
- feeling of constant motion;
- balance issues and dizziness;
- light sensitivity;
- sensitivity to visual information – for example, feeling overwhelmed by being in a small group of people or in the aisles of a grocery store;
- headaches; and
- decreased or slowed processing and difficulty with memory.
These symptoms are addressed in a variety of ways. For example, one of Dr. Johal’s patients was so challenged with absorbing a lot of visual information that he had difficulty getting his words out. She approached his treatment not by working on processing, but by simply working on his eye movements. As a result, he’s talking better, moving better, and is more confident.
Research shows that even a small balanced prescription can be very helpful for dizzy patients. If you need glasses for reading and for distance, it’s sometimes better to put the different prescriptions into two separate pairs of glasses. Progressive lenses can make dizzy patients even dizzier. This is because of how these lenses are made – progressives have a central corridor that’s clear and the rest of the lens has peripheral distortion.
As wearing bifocal glasses can contribute to falls, Dr. Johal recommends dizzy patients have separate single vision glasses just for distance, just for reading, and just for computer use. You may need to have a couple of extra pair of glasses, but as she says, “It’s worth it to be less dizzy.” You may only need separate pairs of glasses for up to a year. Once therapy has improved the functioning of your eyes, you can go back to wearing progressives.
Eye tracking problems – technically known as deficiency of saccadic eye movements – are common after a concussion. Research shows that just over 51% of these patients will have a problem with eye tracking. People with poor tracking become visually overwhelmed by peripheral information. If they walk down the aisle of a busy grocery store, for example, their eyes aren’t sure where to look. Their vision system basically shuts down.
Symptoms of eye tracking problems include:
- skipping, re-reading or substituting words while reading;
- difficulty reading;
- avoiding near tasks;
- poor attention; and
- decreased comprehension while reading.
Testing for eye tracking problems
Eye tracking is measured by connecting you to infrared goggles while you read a brief story. The goggles measure how your eyes move across the page. The goggles are connected to a program that computes the grade level of your reading. The test measures:
- where you are fixating;
- how many times you regress;
- how many words you take in per minute; and
- the average span of recognition - that is, how many words you take in before you stop and pause.
Treatment of eye tracking problems
Dr. Johal said, “I wish I could give patients a pair of glasses that would solve all of these problems but none exist.” However, developmental optometrists can help patients improve eye tracking by working on what is referred to as central and peripheral processing. Patients are taught exercises that are done at home between office visits.
Developmental optometrists spend time measuring how your eyes come together and move apart, both when looking close up and at a distance. This is referred to as eye teaming. Up to 56% of concussion patents have some type of eye teaming dysfunction. Dr. Johal has observed that many dizzy patients have problems with eye teaming. If an object is up close, they frequently are not able to cross their eyes or bring them together. If an object is far away, their eyes often come together short of the target.
Common symptoms of eye teaming problems include:
- double vision (see Figure 2);
- difficulty reading;
- words moving into each other;
- covering an eye when reading; and
- poor ability to look near to far or far to near quickly.
Most dizzy patients say they don’t see double vision but they actually have a component of double vision. They may describe seeing a “ ghost image” or, as one of Dr. Johal’s patients put it, “I don’t see double, but my whole world is slanted.”
Figure 2: Imagine if your vision was like this all the time!
Treatment of eye teaming problems
Problems with vergence cause a lot of symptoms but it’s easy to correct. Developmental optometrists can place prism in glasses and work on exercises with the patient in the office.
Eye focusing problems
People with “normal” vision are able to rapidly bring objects of visual interest into sharp focus without even thinking about it. For those with eye focusing problems (accommodative dysfunction) the eyes and vision system do not focus properly. Research suggests that up to 41% of patients have deficits in accommodation after concussion. Many children and adults are misdiagnosed with Attention Deficit Disorder (ADD) because they can’t eye focus – if things appear blurry, they simply walk away.
Symptoms of focusing problems include:
- intermittent blurred vision at distance, near or both distances;
- visual problems focusing on near tasks, or changing focus from near to far, or far to near;
- headaches, typically frontal or temporal;
- pain around the eyes during visual activities;
- squinting; and
- reading problems, such as difficulty concentrating and having to re-read for concentration.
Testing for focusing problems includes:
- taking detailed measurements of how the eyes are teaming at a distance and close up;
- observing horizontal and vertical eye movements; and
- evaluating how your eye focusing compares with age norms – most importantly, after therapy, the doctor can see how your focusing has changed.
Do you need prism?
Vertical or horizontal prism can be added to glasses to immediately relieve double vision. It’s a simple procedure that could be done in the first eye exam.
Visual Midline Shift Syndrome (VMSS)
Some dizzy patients have problems perceiving their position in space. This can make them think their body midline has shifted to one side or the other. It is very difficult to coordinate your movements when you think everything has moved over to one side.
VMSS is caused by a mismatch between visual and spatial information processed by the brain. It often appears in patients who’ve had a stroke and can occur in up to 50% of patients with Mild Traumatic Brain Injury (MTBI). If left untreated, patients with VMSS will have balance problems and postural dysfunction.
VMSS is really easy to correct with the use of yoked prism and/or therapy. Yoked prisms are a pair of bilateral prisms that are “yoked” (oriented with the base in the same direction). Their effect is basically to shift space. For example, right-yoked prism pushes everything you see over to the left. Yoked prism can be added to shift space either left or right, or up or down.
Figure 4: The effect of yoked prisms is immediate, leaving the patient feeling much better.
If a patient requires only a small amount of prism, about a year after therapy it might not be needed anymore. Some patients may require permanent prism.
Do you wear dark sunglasses and a hat indoors? This will help your symptoms but NOT help healing! Instead of wearing sunglasses indoors, it is much better to use lightly tinted lenses. Every patient is unique – the colour of tint that works best is specific to the individual. Developmental optometrists must test to see which tint is most comfortable for you. Degrees of of tint are graded from one to three – the first is usually enough for comfort indoors. Layers of different colours of tint can be stacked on top of one other when testing; the lab will make a pair of glasses with that precise tint.
Visual field testing
This test evaluates the field of vision to determine any loss or impingement on the optic nerve and its pathway. If the test reveals a problem, the patient is referred on for further investigation.
Damage to the brain from a stroke or other trauma may cause visual neglect. This is a neurological condition that results in not being aware of one side of the body. There are several different cancellation and drawing tasks used to test patients for this type of attention deficit. Figure 5 shows how someone with left neglect might complete several common tests. Another screening tool, the Star Cancellation Test (not pictured here), is more visually crowded than Albert’s Test and catches more patients with visual neglect.
Treatment for visual neglect
One treatment uses yoked prism in the direction of the neglect so that the patient can get more awareness in that field. Different types of visual attention therapy can be tried to bring awareness to the neglected field.
Twenty percent of patients seen by developmental optometrists need no further treatment beyond a bit of prescription in lenses, prism, and tinted lenses. The remaining 80% need active therapy.
Visual rehabilitation can greatly improve quality of life by:
- strengthening the visual system;
- helping to restore balance between the visual and vestibular systems; and
- helping patients return to work and other activities.
Dr. Johal said, “It can be hugely rewarding work. I see patients at my visual rehabilitation centre who’ve been suffering with dizziness for five or six years and after a little bit of work with me they’re back at their jobs.” She emphasized that the rehabilitation process is sped up when the patient does visual and vestibular rehabilitation therapy concurrently.
The average number of visual therapy treatments for dizzy patients ranges between 12 to 16 sessions. Some patients may require up to 36 sessions. A portion of the first exam is covered by the Medical Services Plan of BC – the other two exams and therapy sessions are not covered. The average cost per session is between $115 and $125.