BINOCULAR
VISION

VISIONARY EYE CARE SINCE 1868

WE ARE SPECIALISTS

Sight is one of our five major senses: hearing, touch, smell and taste are the other four. Through our senses we are able to experience the world. But we don’t rely on all senses equally. About 80% of the way we experience the world as children is through vision.

We watch, we read, we learn. We need good vision to read the whiteboard, watch the science demonstration at the front of the class, and catch a ball during PE.

Our vision should allow us to:

  • identify objects
  • track objects
  • perceive depth (see in 3D)

In order for this to happen a clear image needs to be sent accurately from the eye to the brain. Once there it needs to be accurately processed by the brain. In order for this to happen the image is converted to an electrical signal in the eye, which then travels along the optic nerve all the way to the back of the brain to an area called the visual cortex. Here it is translated into ‘what we see’.

In order for this to happen a clear image needs to be sent accurately from the eye to the brain. Once there it needs to be accurately processed by the brain. In order for this to happen the image is converted to an electrical signal in the eye, which then travels along the optic nerve all the way to the back of the brain to an area called the visual cortex. Here it is translated into ‘what we see’.

Most people know that spectacles or contact lenses correct vision. But a surprisingly high number of children (with and without spectacles) have functional eye disorders. A functional eye disorder is where a little piece (or more than one piece) of the visual pathway doesn’t work or works inefficiently. To a child this may appear as blurred vision, difficulty tracking along a line of text, problems remembering what they’ve read, being a slow reader, difficulty catching or hitting a ball, headaches, or double vision. To an adult such as a teacher the child might appear to be a slow worker; they might  mix up words when they read; they might try to avoid close-up work like reading or writing altogether; they might become frustrated, stare out of the window, get up and wander round the class or distract other children.

All of these issues mean that a child’s learning is being disrupted and more importantly, they are at risk of becoming disengaged from education, so it is important that children’s eyes are examined to make sure they are not the cause of the problem.

Unfortunately, you can’t assume that a basic eye examination will look for a functional visual problem. The way the NHS eye test is funded means that only a minimum set of tests needs to be carried out.  If as a parent you don’t know this then you will naturally assume that it covers all bases, but there is a limit to what any optometrist (even a particularly thorough one) can look for in a twenty-minute appointment. Functional visual problems require pretty in-depth analysis.

LET’S TAKE A CLOSER LOOK AT VISION

It’s fair to say that most people think of vision in terms of ‘clear’ or ‘blurry’. If my eyes are healthy and my vision is mostly clear I don’t need to worry about it. If my vision is blurry, I probably need spectacles or contact lenses.

When a normal eye looks at an object, light reflected from it enters the eye through the hole in the middle of the iris which is called the pupil. This reflected light is bent by the optics of the eye so that it focusses on the sensory layer, called the retina right at the back. The retina converts the light to electrical signals travel along the optic nerve to the brain. Here the signals are decoded, and we ‘see’ the image. So, we don’t actually see with our eyes at all, we see with our brains.

LET’S CONSIDER THE TASK OF READING

First our child has to aim their eye at the target. But they don’t have one eye, they have two so now they have the added job of co-ordinating them so they both point at the same point on the page at the same time. Then they have to process the letter they’re looking at, and then they have to move both eyes together, keeping them focussed in the same plane as they track along a line of text. As they’re doing this, they have to process each individual letter, group those letters into words, group those words into sentences. THEN when they get to the end of a line they have to make a quick and accurate sweep back to the left hand side of the page to PRECISELY the line below the one they’ve just read (remembering everything they’ve already read) and do the same thing again, adding all that processed information to the first bit AND making sense of everything as they go. Over and over again. PHEW! It’s a wonder that any of our kids ever learn to read.

Assuming the child has managed that Herculean task the teacher then asks them to write a book review so they have to organise all the information in their heads, and aim both eyes at the same point in the same plane on a blank page, AND on the point of their pen or pencil while they co-ordinate their hand to write the correct letters, grouped into the right words while moving across the page in a straight line. We don’t demand much from the average eight–year-old, do we?

Now you know how complex and finely balanced the process of reading and writing is, it’s probably easier to see just how many things can go wrong: aiming, aligning, focussing, scanning, tracking and processing.

Instead of seeing:

‘The cat didn’t move. It just gave him a stern look. Was this normal cat behaviour, Mr Dursley wondered? Trying to pull himself together, he let himself into the house.’

A child with a functional vision problem who struggles to track, might see:

Thecatdidn’tmove.It just       himgaveasternlook.Wasthisnormaclatbehaviour,MrDursley

wondered.Tryingtopullhimselftogether,     helethimselfintothehouse.

These are just two common examples of functional vision issues and you can see how hard it would be to make sense of all that and actually enjoy the process of reading.

DYSLEXIA

Optometrists are often asked about dyslexia. We do not diagnose it; that is generally a job for an educational psychologist, but it is very important that any child who has a dyslexia diagnosis or is suspected of being dyslexic, to have regular thorough eye examinations.

Dyslexia is a condition which affect the way the brain processes and organises information. It is perfectly possible to be dyslexic and have no vision problems at all. But given that we understand we see with our brains, not our eyes, and that 80% of the information humans process is visual it’s unsurprising that many dyslexics report visual issues.

It is also important to note that it is possible to have really profound visual issues and no dyslexia. Generally, most dyslexics will have some visual issues…but this doesn’t work the other way around! Most people with visual issues are not dyslexic, though they are sometimes identified erroneously as such.

WHAT ABOUT OTHER CONDITIONS SUCH AS DYSPRAXIA, AUTISM AND ADD / ADHD?

We can pretty much say that all dyspraxics have visuo-spatial issues and often have dyslexia too.

Autism is also a condition which affects the way the brain processes information, so it is probably now unsurprising to you that these children often have at least some visual problems.

Kids with ADD and ADHD have brains which are wired differently so may have visual issues running alongside their other difficulties, which can compound their behavioural and learning difficulties.

Children who were very premature babies often have developmental difficulties, including eyes that never developed properly. They almost all have profound visual difficulties and associated learning issues too.

Vision therapy may be able to help many of these children.

HOW DO YOU KNOW IF YOUR CHILD MIGHT HAVE PROBLEMS?

Do they see double?

Some 20% of the population suffer from convergence insufficiency, when it is difficult to turn your eyes in enough to line up together on a near target.

A surprising number of children will admit to this if asked directly. They do not realise that this isn’t normal because it’s always been there for them. In the consulting room many parents don’t actually believe their child because it’s so hard to believe that they never noticed it before!

Do they complain of headaches?

Headaches for functional eye problems usually begin after 10-15 minutes of reading or close work (reading, writing, computer, tablets, playing on a phone etc)

Does their vision fluctuate / become clear then goes fuzzy again?

Do they report finding it difficult to see the whiteboard?

Do they screw their eyes up when watching TV? Do they edge closer and closer?

Do they get accused of daydreaming at school because they are staring out of the window?

Do they complain that words move on the page when reading?

Are they a painfully slow reader?

Do they spend an excessively long time doing simple homework tasks and does homework seem to cause an unnecessary amount of stress?

Do you know your child knows his stuff but then struggles on written tests, misreading questions and making silly mistakes?

Do they complain of discomfort when reading?

Do they have low self-esteem? A child with a functional vision problem doesn’t understand why things are so hard for them. They often think their classmates are smarter because they read faster, get better marks, can pay attention better and may not have to study as much.

At TKS we offer a full binocular vision assessment. This examination takes around ninety minutes and investigates every aspect of your child’s functional vision. We can advise on how best to support and help them with spectacles or contact lenses if required, and / or vision therapy.

What is vision therapy?

Vision therapy is like physiotherapy for the visual system, including the eyes and the parts of the brain that control vision. Vision therapy is customised for each person and can include the use of lenses, prisms, filters, and pieces of equipment. A successful vision therapy outcome depends on the active engagement the child and their parent/s as much as the expertise of the optometrist.

What does it involve?

Vision therapy sessions are booked in blocks of six 30-minute appointments spaced at two-week intervals. The sixth session in each block is slightly longer as some of the original examinations will be repeated to assess how much improvement in binocular function has taken place.

Some problems will be resolved within six sessions while others may require 12 or 18 and a few will require substantially more.

The goal is always to help the child achieve clear, comfortable binocular vision and reduce the eye strain which can act as impediment to reading and learning.