JOURNAL OF THE NATIONAL ACADEMY FOR CHILD DEVELOPMENT
1984, Volume 4, No. 4
The Importance of Visual Pursuits and Convergence
Robert J. Doman, M.D.
Visual Pursuits refers to the coordination
of eye movement as eyes move while reading or following an
object. Each eye is controlled by three sets of two muscles
that work by one muscle opposing the pull of its antagonist
muscle. They include: 1) the superior rectus muscle (which
pulls the eye up) opposing 2) the inferior rectus muscle (which
pulls the eye down; 3) the lateral rectus muscle (which pulls
the eye out) opposing 4) the medial rectus muscle (which pulls
the eye in); and 5) the superior oblique muscle (which pulls
the eye out and up) opposing 6) the inferior oblique muscle
(which pulls the eye out and down). Thus, for one eye to move
smoothly, it requires the cooperation and coordination of
six muscles all working together. For both eyes to work smoothly
together, they require twelve muscles to work together.
It is not surprising, therefore, that
many children have problems in the area of visual fusion and
pursuits, and that NACD frequently recommends visual eye muscle
exercises.
Visual pursuits are a form of fine
coordination. Lack of good visual pursuits causes the individual
to frequently lose his or her place while reading. When this
happens, the child will do one of three things: a) pause until
he again locates his place, which slows the reading time;
b) omit words and continue to read; or c) substitute his or
her own words and continue reading. Omitting or substituting
words can frequently change the meaning of what the child
is reading, causing the comprehension to suffer.
Most eye examinations do not test for
visual pursuits nor do many ophthalmologists treat it. Poor
visual pursuits can be effectively treated by NACD programs,
including the following: crawling, creeping, overhead ladder,
horizontal and vertical tracking, spinning, visual pursuit
activities, black light activities, hand-eye coordination
activities, etc.
Convergence is the ability of the two
eyes to work synchronously together. We can test for convergence
with a pen light directly in front of the eyes one foot away.
The light should produce a reflection of itself exactly in
the center of both pupils. If the reflection is to the inside
of the pupil, the eye is looking outward in an external, or
divergent, strabismus or exotropia. If the eyes fail to converge
perfectly and turn either in or out, this is called a strabismus.
At birth, a child's eyes are not yet
able to converge properly. Convergence must develop in vision
and does so during the creeping stage of mobility. Early attempts
at convergence are inefficient and are called yolking or accidental
convergence. In order for the eyes to learn to converge, the
eye must, with frequency, intensity, and duration, look at
an object at a fixed distance from the eyes. While crawling
on his stomach, there is no fixed object for the child to
see. He can look out at varying distances. If the child misses
creeping on his hands and knees and either sits or stands
and walks, he again sees at varying distances with no fixed
target. Developmentally, only creeping on hands and knees
gives the eyes the ever present fixed target they need. It
is the floor that is at a constantly fixed distance from the
child's eyes, equal to the length of his arms.
If the child has a strabismus, creeping
can help eliminate it. To give the eyes a more distinct target
while creeping, put a small piece of colored tape (one inch
by one inch) on the back of each hand. Use red for the right
and green for the left. While creeping, the child looks at
the hand moving forward.
If the eyes do not converge, each
eye may see a separate picture, causing double vision or diplopia.
Double vision confuses the child. It is like looking at a
T. V. set with a poor antenna causing ghosts or double images.
Because double vision confuses the
brain, it tries to stop it by squinting the eyes. The name
for strabismus was "squint" because many children
squinted to eliminate double vision. The other method that
the brain uses to stop double vision is by the cortex of the
brain suppressing the vision in one eye. If one eye is frequently
squinted closed or suppressed by the brain, it will eventually,
because of lack of use, become weak. This is called "lazy
eye" or amblyopia. This occurs in approximately 4% of
all children. In these cases the child alternately uses one
eye and then, moments later, the other eye. There is less
danger of one eye becoming a "lazy eye."
If a child has a strabismus, strabotomy
or surgery to the eye, should not be considered until the
child has properly completed the creeping stage and until
proper eye exercises have been tried for a reasonable period.
Surgery for strabismus has a poor success rate even when done
early. If the strabotomy is done, follow-up exercises and
creeping can help to improve the results.
NACD uses a variety of specific exercises
to improve convergence. Good convergence, or fusion, leads
to good depth perception. This is the ability to judge how
far various objects are from your eyes. The development of
this ability is essential to many daily activities.
Reprinted from the Journal
of the National
Academy for Child Development
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