What You Need To Know About Your Child's Vision

The greatest common denominator found in brain-injured children is poor vision. Virtually every severely and profoundly brain-injured child has a severe to profound visual problem. In fact, it is very rare to see a brain-injured child, regardless of the severity of injury, who does not have a significant visual problem. Even a modest visual problem can cause a gigantic problem in life since it may prevent a child from being able to read or write.

We human beings depend on our vision more than any other sensory pathway. For this reason the areas devoted to vision in the human brain are larger than those areas devoted to any other sensory pathway. We should not be surprised then, if the brain suffers an injury and oxygen is cut off or decreased for an appreciable period of time, that it is the visual pathway that will suffer more than other sensory pathways from this injury.

The visual column on The Institutes Developmental Profile shows the critical points in the development of the visual pathway. The understanding of this pathway is vital for the parent of a brain-injured child, because it allows mother and father to differentiate between visual problems that exist in the eye and visual problems that exist in the central nervous system - the brain. This differentiation is of the greatest importance.

The old-fashioned practice of treating the symptoms in brain-injured children while ignoring the fact that brain injury is in the brain - not the elbow, the foot, or the eye - has lead to all kinds of inappropriate visual treatments and surgery. These treatments and surgeries are not only ineffective but they can be very harmful to the brain-injured child.

Some doctors do not differentiate between visual problems that arise from problems in the eye and those that originate from a problem in the brain. This is why parents should understand an eye evaluation so that they can review the findings and gain a more complete understanding of what is happening with their child's vision.

Dr. Christopher Weidig kindly consented to walk us through a complete visual examination, making some very important editorial comments along the way. We have not attempted here to give a course in how the visual pathway is evaluated at The Institutes, but instead these are guidelines for understanding and making sense of the typical evaluation your child may have with your eye doctor at home. The following is the result of our tour.

What You Want To Know About Your Child's Eye Examination

GLOSSARY OF TERMS

Unaided Visual Acuity (without lenses)

20/20 is considered average. 20/40 means the individual sees at 20 feet what a person with average vision would see at a distance of 40 feet. An individual who is evaluated beyond 20/40 may need corrective lenses, with the following exceptions:

1. Children, because they are still developing.
2. Any child on The Institutes Intensive Treatment Program, for the very same reason that they are in a dynamic state of change.

Dr. Weidig advises that if an eye doctor does suggest lenses for a child, parents should question why. Ask what result is expected. Have the eye doctor actually place the lenses on the child in the office to observe the difference in performance, if any.

Legally Blind

A person is diagnosed as "legally blind" when he has an acuity measurement of 20/400 with lenses, because such a person would have extreme difficulty reading small print.

Functionally Blind

A person is diagnosed as "functionally blind" when he has an acuity measurement of 20/1000 or 20/1200. Such a person could still move around but large print or magnification of print would be necessary. The end of the chart is a measurement of 20/1600. This was determined to be the vision of a well infant one hour after birth. Dr. Weidig states that it would be rare to find a child with no light perception at all, and extremely rare for to be due to a pupillary abnormality rather than a neurological problem. In other words, the vast majority of children who have no light perception have a brain injury, not an injury to the eye.

Cortical Blindness

Dr. Weidig states that "Among professionals this term actually means we don't know how to test this child; we don't know why he doesn't see. The eye looks healthy but he doesn't respond to testing."

Convergence

This is a coordinated movement of both eyes toward fixation on the same point. When two eyes are focused at the same object, convergence occurs. It is the ability to bring the eyes into the nose to a distance of within three inches.

Phoria

A condition in which they eyes tend to deviate from the normal; a tendency for the eye to diverge or converge, but not continuously. In such a case functional convergence does exist since the child can achieve some convergence.

Perfect Convergence

This is the ability to converge consistently one's vision from far point to a distance of three inches from the nose at near point. Note: The average child holds a book at a distance of eight inches when he reads.

Near Point

Defined as the distance from the end of one's outstretched arm to the nose.

Far Point

Defined as a distance of six meters or more.

Near Sightedness and Far Sightedness

Nearsightedness and farsightedness have to do with the size of the eyes. Often bigger eyes are nearsighted, and smaller eyes are farsighted. Lenses may or may not be needed when either of these situations occurs. Nearsightedness or "myopia" can be an advantage in a near point world. Some children do "outgrow" farsightedness. This happens as the child develops and his eyes literally grow bigger. If such a child is given glasses at an early age, before he has had an opportunity to grow, he will outgrow his glasses and will no longer need them.

Strabismus

A condition in which both eyes can not be focused on the same point at the same time. An overt deviation of the eye in which the two eyes don't function together.

Strabotomy

Eye surgery that may be done on one or both eyes when a strabismus is present. In the case of a child with a convergent strabismus, muscles of the eye are cut in order to pull out the eye that turns in. In the case of a child with a divergent strabismus, the muscles of the eye are cut in order to pull in the eye that turns out. This surgery is a classical example of attempting to treat the symptom and hoping the problem will go away. It does not go away. Often within six months of surgery the convergent or divergent strabismus is right back where it was before the muscles were cut. Strabismus is a result of injury to the brain, not the eye. This surgery is inappropriate, ineffective, and in most cases makes neurological treatment more difficult.

Depth Perception

When a child can not use both eyes together perfectly (strabismus), he will have poor depth perception or no depth perception at all. The percentage of depth perception that an individual has can be measured.

Nystagmus

An involuntary rapid movement of the eyeball, which may be horizontal, vertical, rotatory, or mixed. It is created by the lack of blood supply and, therefore, oxygen to the ocular motor area at the base of the brain (the medulla).

Optic Nerve Pallor

Due to lack of blood supply, nervous tissue appears white or pale rather than pink, as it should appear when it is infused with sufficient blood supply.

Astigmatism

Astigmatism literally means: a-without, stigmatism-focus. This occurs when the curvature of the front surface of the eye or the lens inside the eye is oblong or egg-shaped rather than perfectly round. Due to this defect, when a beam of light passes through, it splits into two points of focus instead of just one. This situation may or may not need to be corrected by lenses. Depending upon the type and degree of astigmatism, a person may be able to compensate for it without lenses. This problem exists purely in the eye. It is an optical problem and not a neurological problem.

Visual Field Cuts

Field cuts are literally sections of the normal visual field that are cut out of that field. Just as we do not have "eyes in the back of our heads," the person with field cuts literally can not see anything in those sections of his visual field where there are cuts. Field cuts are caused by trauma, tumors, aneurysms, strokes, and some forms of cancer, and the subsequent pressure that bears on the optic striations, preventing impulses from traveling down the optic nerves. True atrophy can occur. However, the removal of the tumor, for example, may relieve the pressure in time so that blood flow can resume. In addition, oxygenation may help redevelop blood vessels in the area and thus promote the restoration of full vision. Dr. Weidig states, "It is always worth a try."

Preferential Viewing

This is a test to determine visual acuity. It does not require a verbal response or an ability to read letters or recognize pictures. It is administered by showing a series of striped slides paired with gray slides. It has been discovered that infants prefer to look at patterns rather than at a blank or gray area, and since stripes and gray become indistinguishable at certain sizes or widths of stripes at a set distance, the stripes are arranged to test acuity. After years of using this test, tables have been created that reflect a well child's visual development. These tables can be used to detect aberrations in vision.

Dr. Weidig considers this test to be quite reliable. The eye doctor can evaluate a child's vision by observing the child's eyes and degree of agitation related to the size of stripes on the slides shown.

Strabismus

Dr. Weidig tests for strabismus by covering one eye and then uncovering it to quickly observe the position of that eye at rest. An eye that rests inward (toward the nose) is a convergent strabismus. An eye that rests outward (away from the nose) is a divergent strabismus. An eye that rests upwards is hyper strabismus. An eye that rests downwards is hypo strabismus. Therefore, a child may have a left hyper divergent strabismus or a left eye that goes both up and out. In order to determine near point convergence, as opposed to far point, the child is asked to look at a target at either close or far range as the covering and uncovering test is administered.

Dominance or Laterality

In order to have perfect convergence it is necessary to use both eyes together. However, the dominant eye will take the lead and the subdominant eye will follow. When there is no clearly dominant eye, both eyes will be at war over which one is going to lead and which one is going to follow. This visual tug-of-war results in letter reversals and word reversals in reading and writing. This battle creates tremendous visual inefficiency, and this slows down the child's reading and writing. Anything the child does at near point may be affected by a lack of dominance. (Increasing print size aids the child in this situation, allowing him to use the dominant eye to read despite the dominance problems he may have.) In testing for dominance the doctor wants to see whether the child is right-sided, left-sided or mixed.

Dr. Weidig measures visual dominance only. He does this through a series of tests using degrees of brightness of colors and colored dots configurations in which one eye is shown one image and the other eye another. The individual being evaluated is to indicate by verbal response which color appears brighter or which colored dot configuration he actually sees. As the dominant eye overrides the subdominant one, dominance is evaluated by the individual's response.

With children who can read, dominance is also measured by doing a test using a telebinocular. Each eye sees a paragraph. The paragraph that the right eye sees is identical to the paragraph that the left eye sees, except that the right eye's paragraph uses all feminine pronouns and the left eye's paragraph uses all masculine pronouns. If the child is completely right-eyed he will read "she" and "her" throughout the paragraph. If the child is completely left-eyed he will read "he" and "him" throughout the paragraph. If he sees both "she" and "he" at the same time, or alternates between them, the child has mixed dominance at near point.

Dominance can be evaluated in a non-verbal child using a retina scope and bouncing light off the retina.

Due to acuity problems or strabismus, a child may have to use his subdominant eye in a dominant role functionally in life, because the neurologically dominant eye is made "weaker." As the child's neurological condition improves, this dominant eye will supplant the subdominant eye and take over as the true dominant eye.

The dominant eye also sees colors as being brighter and more vivid, although not necessarily with more clarity. Dr. Weidig suggests that if you want to test this, go out on a bright day and cover one eye at a time. With one eye you should see a greater sharpness of color.

Snellen

This is the standard letter test to determine visual acuity, requiring verbal responses and the ability to read letters.

Visual Evoked Potential

This test involves placing electrodes near the occipital cortex and attempting to measure electrical response to dark and light images that become increasingly smaller. Dr. Weidig considers this test to be unreliable for the following reasons:

1. Children are often sedated in order to administer the test. Sedation can alter function.
2. This test is objective rather than functional. Often a child is just not interested or paying attention when the test is being done. When this is the case, no response will be recorded. This will then be interpreted as actual visual impairment, when it is merely lack of attention or interest.

Lite House Cards

This is a test in which cards with pictures are shown to determine visual acuity.

Involuntary Nystagmus Test

A striped drum is spun, creating an involuntary nystagmus in a seeing individual. No such response is seen in a child who cannot see. If a child does not respond to the test it is assumed that the child cannot see. Once again, Dr. Weidig does not consider this test reliable, as a child may not have his attention or interest engaged and thus be unresponsive, even though he may be able to see.

Eye Coordination

Eye coordination is tested at both near point and far point to see how smoothly and easily the individual can coordinate his vision.

Eye Movement

Here the eyes are examined in all meridians related to the third, fourth, and sixth cranial nerves. Structural damage and subsequent scar tissue can cause restricted movement, as does a strabotomy.

Color Vision

Dr. Weidig uses the City University Matching Test to evaluate red and green discrimination. This test uses a configuration of dots in which the child is asked to point, blink, or in some way match colors. Congenital problems can be evaluated in this way. This test also evaluates yellow and blue deficiencies. Such deficiencies may indicate problems such as cataracts or neurological problems.

Internal Eye Health

This is an examination of the internal eye structures: blood vessels, nerve tissue, and optic nerves. When the blood supply is insufficient, optic nerve pallor or paleness may be observed. This would be typical in a child with poor visual acuity (20/800).

Dr. Weidig points out that "The term optic nerve atrophy is likely to be used incorrectly in a young child in this situation, as it implies the optic nerve has withered. Whereas the term optic nerve dystrophy would be more accurate, since this indicates the child has not yet used the optic nerve fully and the blood supply has not yet been sufficiently tapped."

External Eye Health

Here eye doctors observe the various external structures of the eye, such as the pupil and the iris.

Refraction

If corrective lenses are indicated due to problems of visual acuity, a prescription is then given. Dr. Weidig uses lenses only when the need is great and the child cannot develop without them.

by Janet Doman, Director
The Institutes for the Achievement of Human Potential
and Susan Aisen, Director
The Institute for the Achievement of Intellectual Excellence