Behavioural Optometry
Vision and Learning
From the moment a child is born he is learning and developing rapidly. Much of the information about his new world is received through the eyes, so their health is of paramount importance from the earliest age. For this reason the Health Authority recommends regular eye tests at yearly intervals until sixteen years of age.
How does the eye work?
The retina at the back of the eye is primarily a relay station which transforms visual stimuli (light falling on it) into nerve messages to the brain. But its function is not the same all over. The central or macula area is sensitive to fine detail enabling us to see an object clearly, but the surrounding or peripheral retina 'sees' only a blurred picture, responding instead to movement, direction and change in the environment, giving us a 'picture' or 'frame of reference' within which we can select an area for attention. This allows precise positioning or aiming of the eye so that the object of interest falls upon the central area allowing it to be seen clearly. Centre and periphery must be in perfect balance so that our 'picture' is as large and detailed as possible, enabling us to accurately and efficiently select an area and then direct our attention to it.
Binocular or two eyed vision (eye teaming)
The situation is further complicated by the fact that we have two eyes and each must be accurately aligned upon the object of interest in order for the two identical pictures of it to be relayed to the brain and fused or superimposed to give us a single picture.
Because of the distance between the two eyes only the central objects at the distance or plane of regard are superimposed exactly, and the similarities and differences in the rest of the field give valuable information about depth, relative sizes, distances, and solidity of objects. Binocular vision is reliant upon convergence or turning in of the two eyes upon an object in near space so that it falls on the macula of both eyes simultaneously. Both eyes must be in perfect synchrony as they track an object across space or moving towards or away from us in space, despite object and/or head and body movement. Therefore vestibular and muscle proprioceptive systems (giving information on balance and the position of eyes in relation to head, head in relation to body, and the body in space) must integrate (co-operate) with visual information to maintain this steady fixation. When attention is directed from one portion of space to another then a fast saccadic jump is made and the two eyes must arrive at the exact same spot at the exact same time.
What is behavioural optometry?
Behavioural optometry is based on an understanding of the developmental sequence of learning and growth within the human visual system. In particular its interaction with (and dependence upon) the other sensory-motor systems of the body for optimum development. The testing investigates the adequacy of functional (performance) visual skills. In the absence of disease, and with all the necessary 'bits' present and in 'working order', is the visual system operating to the level that this individual requires in order to go about their daily business. Obviously these requirements will vary with the individual. An elite athlete will not require the same skills as a child in school or an individual researching information upon the Internet all day.
Behavioural Optometry looks at an individual's understanding of their visual space world and the features within it. This can be represented by their ability to successfully select and then centre in upon, or attend to, the chosen area of space with both eyes simultaneously, to hold it for as long as necessary to complete a task, to release it when required, and then to select and redirect attention to another portion of space. This should be accomplished with the maximum efficiency, accuracy and freedom from distraction, but minimum effort. Visual skills should be at a low level, subconscious and requiring only minimum attention. If they are sufficiently poor to require high-level conscious brain activity then they compete with comprehension during classroom activities. For example, during writing they can hamper the flow of thought processes and either writing skills or content will deteriorate. The goal of a highly functioning visual system is to obtain meaningful data from the environment, based on present incoming information and past knowledge and experience, in order to guide action which may be physical or mental (movement in relation to, or action with respect to a particular environmental component). Vision is much more than simply seeing clearly. It is the entire process whereby an individual understands what he sees. Vision is the learned process of making sense of light energy entering the eyes so that we may usefully, and with maximum efficiency, embrace our environment.
Are we born with good vision?
The ability to control the visual system so precisely is a learned process that begins in the womb, continues in the baby and toddler, and needs to be well organised on entering formal school if a child is to have maximum learning potential. To develop a well functioning, efficient visual process capable of a myriad of demands requires the individual to have had many, many developmental opportunities in his early years. Visual learning occurs along side, and is dependent upon, early movement for its development. First, movement directs vision (exploration of objects in mouth and manipulation with hands, followed by visual examination) and then, vision directs movement as a baby rolls and then crawls and then walks towards objects of interest. Information is matched, and rematched, between the sensory and motor processes as they develop. Limitations or mismatches within one system will, therefore, alter experience and effect how information can be matched resulting in imbalances or inaccuracies within all system. As time goes on these mismatches remain within the system warping further development.
How does vision differ from sight?
Sight is the first step in getting ready to see something. The eye is rotated until light from an object of interest falls onto the macula area of the retina. This enables us to resolve, or 'see', the small detail of the object. Sight is the initial response to light. Vision is the process of interpreting what is seen, of extracting meaning, or making sense of, a visual situation, and of integrating this with information also received from the other senses. This allows us to direct, or co-ordinate a chosen action in response. This may in the form of body movement, such as reaching out to pick up a cup, or mental movement, such taking meaning from printed text in a book.
Why is this important?
Good sight is important in the identification of an object. Good sight is important in the awareness of small similarities and differences between objects and this is essential for the correct identification of a letter or number. However, good sight is just one of many measures of performance that are essential to good vision.
So what is behavioural optometry?
Behavioural Optometry investigates the efficiency and resilience of the human visual system to cope with the demands placed upon it in every day situations. In other words, Behavioural Optometry assesses the functional fitness of the visual system to serve our individual needs on a day-to-day basis. Sight is one of the many criteria used in assessing overall visual performance.
Functional fitness of vision to do what?
Behavioural Optometry investigates the functional fitness of the visual system to extract meaning from a visual situation, in order to direct appropriate action, either physical or mental. On some occasions functional fitness may simply mean good spatial information to navigate our body and limbs through space without bumping, tripping or colliding into moving or stationary objects as we stroll down the pavement. For an ice hockey player it may mean a superior ability to anticipate, at speed, the exact point at which a fast moving puck will make contact with his moving stick, whilst simultaneously taking account of, and reacting to, the threat of opposition players moving in to tackle. Both situations involve visual skills. Information received through the body and eyes, combined with prior experience, allow the hockey player to judge the speed of the moving puck and assess the force with which it would have to be hit, on this particular occasion, considering it's present speed and direction, in order to achieve a desired result.
Incoming visual information enables us to extract meaning or understanding from any visual situation. This 'understanding' allows us to direct, or co-ordinate, a chosen action in response. We see a lamppost in our path. We immediately know from past experience that it is hard, a collision will hurt, and the lamppost will not move out of the way. We have to go around it. Vision is continuously informing us of the lamppost's exact position in space relative to our moving body. This allows us to instigate an appropriate action or response, a change in direction, to avoid the obstacle.
On another level, what you see may result in a mental, rather than a physical, action with respect to the target. If, whilst walking, you see person you had hoped to avoid, the meaning or understanding that you extract from the visual input will immediately initiate mental activity. What will you do? How will you avoid being seen? Should you pretend that you haven't seen him and divert into the nearest shop?
Do we all see the same?
Vision is the product of inherited potential, past experiences and current available information. From these two examples you can see that it is not only the present visual input, or what is 'out there', that is important in seeing. Past experience, or what we already know, also influences the way in which we respond to visual input. What we bring to the visual situation from the past effects how we deal with a visual situation in the present. If a fast moving puck hurtled towards many of us we would run, duck or scream. We have no past experience that would enable us to deal effectively with the situation. And, if we had never previously met the man walking down the street then we would not recognise him. We would not know that he is best avoided and would not deviate from our chosen path. If we had never been exposed to letters and words, this page of text would have no meaning. We would not 'see' a story. We would simply 'see' a page full of rows of small squiggly symbols.
What about the classroom?
These were simple and, hopefully, easily understood examples of visual input enabling us to derive meaning, or make sense of, our visual world, and then direct action in response, either in the form of body movement or mental movement. Much more complex is to consider a classroom situation. Here much of the body movement is so small that it is easily overlooked. Incoming visual information instigates small eye movements across the page, or back and forth to the blackboard. It guides precise hand movements over the page in drawing and writing. Invisibly, it also co-ordinates the muscle activity that controls the focusing mechanisms of the eye, to home in at a particular distance in order to direct or maintain attention. Simultaneously, it directs mental action with respect to the visual scene. Information is absorbed, processed and integrated with feedback from other senses. This involves a multitude of visual perceptual skills, visual discrimination, figure ground, closure, memory, sequential memory and form constancy. The body remains upright and essentially stationary, with only small and very specific movements required. The body must be in perfect balance with gravity. Feedback systems must be continuously monitoring body and limb position. Small groups of muscles must act in isolation, their action refined so that eyes may move without head and fingers without hand and arm. A sophisticated integration of mind and body, of body and senses.
How is all this possible?
A child must learn all that he knows. He must even learn how to learn. He is born with an innate response system in the form of reflex actions. Examples are the suck, blink and startle reflexes. Reflex actions are the springboard for the development of movement. They precipitate early movement patterns. Through rolling, crawling, creeping, and walking a child gains control over his body and limbs. He develops an understanding of his body parts, of his orientation relative to gravity, of his two sides and how they interweave. He gains an understanding of top and bottom and left and right, of the importance of orientation and directionality. Using movement, steered by his eyes, he moves towards, away from, under, over, and around. At this stage movement is necessary for exploration and manipulation of his world. He projects his internal understanding of orientation, sidedness and directionality out into space to create a unique visual space world that is his own. A map-like representation or understanding of what is 'out there' based upon his own unique experience of the world. This continuously developing three-dimensional map enables him to navigate his way through space, to understand where he is relative to the world, where objects are relative to himself and to each other. Feedback from other senses help him refine his space world so that it matches with reality, so that it becomes a true representation of what is actually 'out there'. He learns control over his eyes, to reach out with his eyes, to grasp, to hold and then release objects with his eyes, to manipulate them with his eyes, to jump, to follow and to look from near to far. Now he is learning efficient visual inspection of his world so that he may use vision to obtain information without the need for movement. Now he can examine parts of his world that he cannot physically reach. Through speech he is increasingly able to sort, categorise and label his visual world, to describe and to communicate his visual world to others, and, through language, to share the visual world of another. Now he no longer needs to personally 'see' or experience a visual event in order to 'know' or understand that event. Language and vision come together to form a powerful tool to represent, to manipulate, to combine and to communicate ideas to others. Language and vision combine to think and to analyse, to imagine ideas, to communicate with himself. Visualisation, Visual comparison, visual memory, visual projection all allow him to attach meaning to two-dimensional symbols such as numbers and words. Now he can explore his world ever more deeply. Indirectly, he can communicate with those he has never met, through the printed word.
So what does a behavioural optometrist actually look for?
In addition to the usual sight problems, the skills that a behavioural Optometrist has a particular interest in fall loosely into these four categories. All can occur even when sight (the ability to see small detail) is within normal limits and all frequently result in a learning related visual anomaly.
EYE FOCUSING SKILLS - This relates to the ability to direct attention across space and to maintain attention without undue fatigue. Clear sight and good hand to eye co-ordination and spatial awareness are dependent on good focusing facility. Poor skills may result in slow speed of work, short attention span, fatigue, difficulty with blackboard copy work and 'clumsy' behaviours.
EYE TEAMING SKILLS - The two eyes work most efficiently as a pair and deficiency in eye teaming skills (binocular instability) hampers all judgements of spatial position, relationships, depth perception and the immediacy and accuracy of single clear vision. Symptoms of visual stress, such as skewed posture, blinking, squinting, headaches, poor concentration, double vision and poor general co-ordination may be evident.
EYE MOVEMENT SKILLS - this is the skill of speed and control of visual inspection. If eye movements are slow, uncoordinated or clumsy, or require more that their share of energy, then a child will lose their place, make excessive head movements, need to use feedback from another sensory-motor system to guide vision (finger under print) or fatigue prematurely. The amount of visual information received will be reduced, resulting in slow copy speed, excessive head movement on copy work, and omission.
VISUAL HIERARCHY - Vision should emerge as the dominant sense. When we 'touch' our world with our eyes, vision will trigger sensory-motor responses in other sense systems that may enable us to smell, taste or feel on object simply through sight. If we have a well developed visual system Vision should trigger a sense of all that we 'know' of the object through past experience so that we truly 'understand' that object. For example the sight of an empty cup may make us feel thirsty. We know immediately the other forms that a cup could take and the different uses to which it may be put. We may taste a drink that we fancy, or feel hungry as thought of associated foods is triggered. If a child has to physically touch the target, or depend on any other sensory feedback to trigger these reactions, then vision has not developed a dominant role and this child will not take all that is expected from a visual situation. He will need additional information through other senses if he is to succeed.