What is vision development?
Many children have a vision problem, which significantly limits present performance and could limit future potentials, and yet they have no eye problem. They have healthy eyes internally and externally, no optical defects and have clear sight at six meters (100 per cent or 6/6 visual acuity), yet they are unable to effectively control and use their system to obtain ‘meaning’ from the environment.
The vision development process is a complex interaction of growth, experiences, learning and practice. Self-generated movements play a critical role in the development of efficient visual skills.
A normal healthy baby is born with the ability to see and move the eyes, though this is initially stimulus bound. That is, the infant is attracted to light and stimulated to turn towards bright objects or moving objects that stand out. The infant also looks as a reflex response to noise or touch. At first the infant tends to move his or her head to look, but later moves eyes alone to look and follow whatever has stimulated them.
The baby touches what he or she sees and learns to associate the feel and look of objects. Similarly, the baby puts objects into the mouth or smells or listens; so that an association occurs with all sensory inputs and what he or she sees. In time a baby can know how an object feels, sounds or tastes by looking alone. With practice, he or she learns accuracy of coordinating eye and hand movements. Experience of what is ‘far’ and what is ‘near’ comes from moving himself through space and seeing things from different points of view. Eventually judgments of distance, shape, size are refined and the infant learns that he can depend upon what he sees without the need to touch, mouth or taste.
As children develop, they learn to use their vision. Initially the conscious mind is significantly involved in both planning and managing appropriate visual responses. But later pre-programmed mechanisms for action and thinking ‘schemata’ free the conscious mind from the mechanics of the tasks. These schemata enable greater comprehension and assimilation of the available information. When a child is experiencing school difficulties, one of the factors which should be carefully checked is the adequacy of the ‘schemata’ that underpin efficiently visually directed behaviour and visual inspections.
Expect your optometrist to give careful consideration to your child’s emerging visual abilities and to relate this information to the age expected and school demands. Some of the important visual skills that need to be considered are:
1. Visual problem solving style
How a child deals with problems that require visual discriminations and judgments is influenced by previous experiences with similar tasks. Some children persistently demonstrate impulsive responses. Does your child show poor attention to visual detail; take little time to analyse available details and give rapid responses; and often need to ‘touch’ things that could be expected to be analysed by visual inspection only?
2. Direction concepts
For optimal processing of visual information, directional responses should be completely accurate and automatic. This ability gradually comes as children relate to the ‘sidedness’ on their own body (right/left awareness), and project this understanding of direction onto the processing of direction – coded information such as “b, d”, “on, no”, “was, saw” and “31, 13”. Children develop an understanding of themselves as a point of reference for developing spatial concepts and making judgments of direction. From an understanding of ‘where I am’, the position of objects and their sequences, the ‘where it is’ takes on meaning.
3. Visual analysis skills
The ability to make accurate visual discriminations, sometimes called form perception, gradually emerges. What is the child’s ability at making judgments of size, shape, position and distance? Can he or she remember what is seen and visualize objects in different spatial orientations? The ability to visually inspect details and then to reproduce (copy) the form involves the use of visual analysis skills to plan the copy movements.
4. Hand-eye coordination
The ability to team eyes and hands as ‘learning tools’ is obviously important to the child in the classroom. What is the child’s ability to visually plan and perform a task in a defined spatial area?
5. Eye movement control
Can the child follow moving objects smoothly, accurately, effortlessly? Can the child quickly and accurately look from object to object, from far to near to far, and sustain such activity without undue fatigue or discomfort. Are these movements relatively automatic, or are they demanding on the conscious mind?
6. Eye-focus skills
Is it easy for the child to quickly focus from near to far etc. and get clear detail with each change? Can the child sustain focus at the near task without fatigue, blur or discomfort? Often children with focus problems pull the book very close and make the print appear larger. Others avoid sustained close tasks.
7. Eye-training skills
How well do the two eyes work together on far seeing tasks; and near seeing tasks? Can they sustain their teaming so that accurate single and clear information can be obtained without effort, fatigue or discomfort? Eye teaming problems often cause difficult in sustaining visual attention.
Given the importance of efficient visual function it is recommended that ‘vision development’ not be left to chance. Ideally all children should be examined at the following stages:
- At age six months.
- At age two and a half years.
- Before commencing school.
- Yearly thereafter.
Your optometrist will be checking to ensure that your child’s visual abilities are appropriate for age. If all this is so, then guidance suggestions about games, toys, etc. that can be utilised to enrich your child’s experiences could be expected.
Some children demonstrate obvious visual difficulties and need to be taught how to control and synchronise the following, focusing, aiming and teaming movements of their two eyes while involved in information acquisition. An intermittent eye turn in a child over six months of age is not normal and early treatment is recommended. Optometric Visual Training is the treatment of choice for many visual dysfunctions.
Stress induced visual problems
After the child has developed efficient visual skills, they are still ‘at risk’ if exposed to excessive near seeing demand and prolonged adverse stresses on the visual function. Indeed, stress induced visual co-ordination difficulties can result at any age. Just as our timing and movement management will deteriorate when any of our skills are exposed to excessive demand and adverse stresses, so will the visual co-ordination skills deteriorate. Thus, a stress induced vision problem may result which will limit the person’s ability to visually perform with efficiency, comfort and accuracy for any sustained time. Avoiding close visual tasks eliminates symptoms, but otherwise, depending on the degree of deterioration of the visual function some or most of the following symptoms are usually produced.
Symptoms due to fatigue caused by extensive demand on the neuromuscular system:
- Headaches or aching eyes; pain referred to the muscles of which an excessive effort is demanded. Such symptoms are often associated with excessive or prolonged use of eyes and will disappear or significantly reduce with withdrawal from, or avoidance of, visually demanding tasks.
- Difficulty changing focus from near to distant objects or vice versa. Inability to quickly make a distant object clear after sustained close reading without blinking or squinting.
- Glare discomfort, usually only partly relieved by sunglasses, but characteristically reduced by squinting one eye.
- Reading comprehension and efficiency drops after a short time on a task.
Symptoms due to failure to maintain constant singular binocular vision:
- Blurring of print (goes funny) or running together of words while reading.
- Intermittent double vision under conditions of fatigue.
- One eye turns without double vision (usually noted by family or friends).
Symptoms due to defective postural sensation:
- Difficulty in judging distances and positions, especially of moving objects. Timing judgments for hitting and catching small balls are usually difficult.
- Bumping into objects or misjudgments of position of objects when involved in active visually directed movement and game play.
- Feeling of insecurity when dealing quickly with steps, escalators or parking the car.
Performance lenses: Because our culture makes such high demands on near vision, reading glasses are frequently of value in eliminating or reducing discomfort, and or improving performance. Performance lenses are ‘tools for the job’ of sustained near looking, and are used as a measure to prevent stress induced vision problems; and equally importantly, to enhance visual achievement on the printed page. They are usually low power lenses but may blur far seeing. Bifocals may be considered, the upper portion with a compensatory power or no power, if lots of looking far and near is demanded. Alternatively the patients may be instructed to look over the reading glasses.
Training lenses: Some visual function disorders can be treated by doing specific activities while wearing lenses that modify the focus teaming relationship. These lenses often initially disturb performance but become easier to tolerate as improved visual control is developed. Training lenses are used routinely during formal visual training and sometimes as a ‘tool; during passive training.
Compensatory lenses: Eye focus disorders result when some eye components are too large, poorly curved or aged. Refractive compensation for such conditions as near sight, far sight and astigmatism, is usually achieved by either contact lenses or glasses.
With age, the lens inside the eye gradually loses elasticity. This normal age process commonly results in increasing near focus difficulty. After age 40 to 45 reading glasses are usually needed to compensate for the lost focus power of the presbyopic eye.
Progress reviews: Four to eight weeks after a patient has been wearing the new prescription directed at modifying performance, a progress review is recommended evaluation ensures that the expected performance changes have indeed occurred and identifies the patients needing Visual Training. Counseling of the patient may need repeating to improve visual hygiene, e.g. poor lighting, work habits and posture that can aggravate an already fragile functioning ability.
Optometric visual training: Since most visual/perceptual skills are learned, they can generally improve with practice under controlled conditions. Many visual problems cannot be adequately treated by glasses or contact lenses alone. Visual training is prescribed to improve turned-eye and lazy eye problems, and to help patients learn, relearn or reinforce specific visual skills. For patients who are motivated, willing to practice and follow instructions, significant progress towards more efficient or comfortable visual performance usually results. There is no ‘typical’ program, since each patient will have individual needs. Usually patients are seen once per week for in-office treatment and are given procedures to practice daily at home. Appropriate lens support is always an essential component of visual training management.