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Microsoft Word - Printable .pdf - Pediatric Vision
DisordersPediatric Vision Disorders
Click Here for Important information On How to Get the Most out of
this Course
Course Introduction
This course covers pediatric vision disorders which may be
encountered by professional opticians in the course of their day to
day activities. This information can help them understand the needs
and communicate more effectively with their young patients and
their parents, and the prescribing practitioner as well. Amblyopia,
sometimes called "lazy eye," is loss of vision without any apparent
disease of they eye. It usually occurs in childhood and affects
approximately 2 or 3 out of 100 people. When one eye develops good
vision while the other does not, the eye with poorer vision is
called amblyopic. Since the best time to correct amblyopia is
during infancy or early childhood. Parents and eyecare
professionals must be aware of this potential problem. The course
begins with a discussion of amblyopia and some of its possible
causes such as anisometropia, strabismus, cataracts, and ptosis.
Since congenital cataracts can be the cause of the most severe
forms of childhood amblyopia, this subject is covered in greater
length. And since strabismus is the most common cause of amblyopia,
that subject, too, is given special attention. Treating amblyopia
is also covered which includes the use of spectacle or contact lens
for the correction of anisometropia or aphakia, surgery in cases
involving strabismus or ptosis, and patching to help restore good
vision to the affected ambylopic eye. Increasing numbers of
children are participating in sports at an early age. It is the
responsibility of the parents, coaches and eyecare professionals to
provide protective eyewear and enforce its use. This course covers
eye safety for children in home, school and while participating in
sports. The course continues with the subject of vision and reading
and discusses children's problems with reading, learning, and
behavior caused by convergence insufficiency, tracking problems,
esophoria, exophoria and other visual problems. It discusses the
role of visual training as a solution to learning disability
issues. Contact lenses can provide children with many of the same
optical advantages as they do adults. These include better
peripheral vision, less distortion, and less troublesome image size
differences. Contact lenses can eliminate the unwanted prismatic
effects of spectacles, and the hyperopic patient will experience a
decreased accommodative demand when using contact lenses. Since
contact lenses can provide a viable solution for certain childhood
vision disorders covered in this course, the subject of contact
lenses for children concludes this course.
Amblyopia
Amblyopia—Amblyopia is a medical term which describes poor visual
development. A child or an adult with amblyopia has poor visual
acuity (clarity or sharpness of vision in one or both eyes). The
word comes from the Greek. [ambly- (dull) + -opia (vision)]
Amblyopia is often referred to as “lazy eye.” The main causes for
amblyopia, or poor visual development, are the following: (1)
Abnormalities in the refractive power (or focus) of the eye. (2)
Misalignment of the eye, or strabismus. (3) Cloudiness of the
normally clear visual pathway, such as from cataract or other
abnormalities.
Anisometropia—A Possible Cause of Amblyopia (unequal focus
refractive error). Anisometropia occurs when the refractive error
of one eye differs significantly from that of the other eye. If
asymmetric refractive errors are present in a young child, one eye
sends a clear image to the brain and the other eye sends a blurred
image to the brain. The brain pays attention to the clear image,
and ignores or “turns off” the signal from the blurry eye,
resulting in poor visual development. This is the most difficult
type of amblyopia to detect since the eyes may look
Copyright © 2013 Optical Training Institute – Irvine, California
2
normal, even though the vision in one eye is significantly worse
than the other. The treatment for this type of amblyopia is glasses
to correct the anisometropia. Glasses alone do not always improve
vision to normal, however. Patching of the better eye is often
required in order to stimulate the brain to use the amblyopic or
“lazy” eye. Occasionally, glasses alone are all that is required to
improve the vision back to normal in this type of amblyopia.
Strabismus—A Possible Cause of Amblyopia Amblyopia caused by
misalignment of the eyes occurs w hen the eyes either cross in,
wander out, or misalign in a vertical position. In this instance,
the child will see double for a brief period, then the brain will
begin to ignore or suppress one of the eyes to avoid double vision.
This can lead to a severe from of amblyopia, and may occur in half
of the children whose eyes misalign. Some children who have
misalignment will maintain good vision in each eye by alternating
looking with one eye and then the other. Patching the straight eye
will improve the vision in the misaligning eye. However, treatment
for the poor vision does not straighten the eyes. This often
requires surgery, glasses, or eye exercises. Strabismus is
discussed in more detail later in this course.
Cataracts—A Possible Cause of Amblyopia The cause of the most
severe type of amblyopia is cataracts in infants. This is best
treated by surgically removing the cataract, correcting the optical
focus of the eye, and doing intensive patching at a very early age.
This is usually done in the first few months of life, and is
continued throughout childhood. Cataracts are discussed in greater
detail later in this course.
Treating Amblyopia The mainstay of treating amblyopia is patching,
either full-time during waking hours, or patching the good eye
full- or part-time. The younger children are, the shorter the time
course required for treatment. Older children, aged six or older,
may require months of patching to restore normal levels of vision.
Once vision has been restored with therapy, part-time patching or
maintenance patching may be required to keep the vision from
slipping or deteriorating. Prompt treatment is both a
responsibility and an opportunity.Whenever strabismus or amblyopia
is suspected, the child should be seen by an eye specialist as soon
as possible. Early diagnosis and treatment are the keys to
restoration and preservation of good vision in children
How is amblyopia diagnosed? It is not easy to recognize amblyopia.
A child may not be aware of having one strong eye and one weak eye.
Unless the child has a misaligned eye or other obvious abnormality,
there is often no way for parents to tell that something is wrong.
Amblyopia is detected by finding a difference in vision between the
two eyes. Since it is difficult to measure vision in young
children, the ophthalmologist or optometrist often estimates visual
acuity by watching how well a baby follows objects with one eye
when the other eye is covered. If one eye is amblyopic and the good
eye is covered, the baby may attempt to look around the patch, try
to pull it off or cry. Poor vision in one eye does not always mean
that a child has amblyopia. Vision can often be improved by
prescribing eyeglasses. A comprehensive eye exam will include an
examination of the interior of the eye to see if other eye diseases
may be causing decreased vision. These diseases include: ·
Cataracts; · Inflammations; · Tumors; · Other disorders of the
inner eye.
Loss of vision is preventable Success in the treatment of amblyopia
also depends upon how severe the amblyopia is and how old the child
is when treatment is begun. If the problem is detected and treated
early, vision can improve for most children. Sometimes part-time
treatment may have to continue until the child is about nine years
of age. After this time, amblyopia usually does not return. If
amblyopia is first discovered after early childhood, treatment may
not be successful. Vision loss from strabismus or unequal
refractive errors may be treated successfully at a much older age
than the amblyopia caused by cloudiness in tissues in the
eye.
Copyright © 2013 Optical Training Institute – Irvine, California
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When should vision be tested? It is recommended that all children
have their vision checked by their pediatrician, family physician,
optometrist, or ophthalmologist at or before their fourth birthday.
Most physicians test vision as part of a child’s medical
examination. They may refer a child to an eye specialist if there
is any sign of an eye condition. New techniques make it possible to
test vision in infants and young children. If there is a family
history of misaligned eyes, childhood cataracts or a serious eye
disease, an ophthalmologist can check vision even earlier than age
three.
More on Cataracts
Cataract (cloudiness of the crystalline lens). An eye disease such
as a cataract may lead to amblyopia. Any factor that prevents a
clear image from being focused inside the eye can lead to the
development of amblyopia in a child. This is often the most severe
form of amblyopia.
Cataract is a clouding of the normally clear lens inside the eye
and is known primarily as a common cause of poor vision in older
adults, but it also occurs uncommonly in babies and children. When
cataract is present in both eyes, family members can usually tell
that there is a problem with vision. When only one eye is affected,
the child most often seems to see normally. A cataract may make the
black pupil of the eye look white or gray. Sometimes eyes with
cataract wander out of line, or show jiggling movements
(nystagmus). Often, though, the child’s eyes look perfectly normal
to family members. Cataract in childhood may be caused by injury to
the eye, or by a problem with the child’s general health. Sometimes
it is passed on to the child by heredity, usually from a parent who
has had the same problem.
The crystalline lens is located behind the colored iris and it
functions to help focus light entering the eye. When cataract is
present, vision is lowered because light cannot properly reach the
retina. Glasses alone are not able to bring back sight lost because
of cataract. In some cases, vision loss is so mild no treatment is
necessary. Usually, though, the cloudy lens must be removed with
surgery before the eye can see well. Cataract surgery is a major
eye operation that must be done with the child asleep under general
anesthesia. It can be performed at any age (even in babies just a
few days old). Most of the lens is removed using very delicate
surgical instruments (not a laser) through a small opening into the
eye. Usually the child feels little or no pain, and goes home a few
hours after surgery. The eye needs to be examined in the
ophthalmologist’s office the next day, and several more times
during the next few weeks. The child has to wear a protective
shield over the eye for a while, and activity is restricted for up
to one month.
To see their best after cataract surgery, children often need to
wear glasses, and sometimes contact lenses. Without these, vision
may stay low. Many children, especially if they have had a cataract
in only one eye before age 5 years, need treatment for amblyopia
after surgery. Usually this involves placing a patch over the good
eye for at least a few hours a day, forcing the child to use the
other eye. Children often object strongly to wearing a patch, but
unless this treatment is effectively done, vision may never recover
from the harm caused by the cataract. The first few months after
surgery are the most important time for treating amblyopia, but
usually some amount of patching must be continued up to about age
10 years. Most children who are treated for cataract end up seeing
well. Occasionally, though, even with the best possible treatment
vision stays low.
When the crystalline lens is removed about 15.00 diopters of plus
power is also removed from the optical system of the eye and must
be replaced. There are at present three commonly used ways to fill
this refractive need. The first is with eyeglasses. The main
advantages of glasses after cataract surgery are that they carry no
risk of harming the eye, and they are very convenient and
Copyright © 2013 Optical Training Institute – Irvine, California
4
simple to use, and they often produce sharp vision. The main
disadvantage is that they are generally quite thick, and older
children (teenagers) may object to their appearance and may find it
difficult to play sports in them. Also, glasses are generally not
good for use after cataract surgery on one eye only; the images
from the two eyes cannot be properly fused due to the difference in
magnification between a plano or low powered and an aphakic lens
containing 10 or more diopters of plus power.
The second way to fill the refractive need of a child who has had
cataract surgery is to use contact lenses, which are worn directly
on the cornea. Contact lenses usually provide both vision and
appearance that is very natural. They can be used after cataract
surgery on one or both eyes. Children of all ages usually are quite
comfortable wearing contact lenses. Lenses are available that can
be worn continuously for about a week at a time. It is important,
though, to remove them regularly for cleaning. The main
disadvantages of contact lenses after cataract surgery are that in
young children (especially between about 1 and 5 years of age),
placing them in the eye and removing them for cleaning can be
difficult, and they can be lost when the child rubs the eye and so
in some cases need to be replaced fairly often. With babies and
school age children, family members usually learn to handle contact
lenses well in a short time. Contact lenses are very safe when
properly cared for. Rarely, though, they can cause serious eye
infections, especially if care instructions are not followed. Some
children wear contact lenses part of the time and glasses part of
the time, depending on their particular needs or wants at the
moment.
The third way to provide refractive correction after cataract
removal is by implantation of an intraocular lens, or IOL. An IOL
is a tiny object that is placed inside the eye surgically, usually
during the same operation in which the cataract is removed. IOLs,
like contact lenses, usually provide vision and appearance that is
very natural. Their main advantages over contact lenses are that
once in place usually the only attention they need is regular
check-ups by the ophthalmologist, and they are present constantly
to do their job, so the child never has to put up with blurred
vision even for a short time. The primary disadvantage of IOL
implantation is that once the lens is inside the eye, it is very
difficult to remove or replace. This is important, especially for
younger children, because as the eye grows and matures, the
refractive error can change quite a bit. For this reason, the child
who has had IOL surgery may still need to wear glasses or contact
lenses at certain ages, although they do not have to be as strong
as what would be needed without the implanted lens. IOLs have been
used in a very large number of adults who have had cataract surgery
within the past 15-20 years, and have been found to work very well
and to be very safe.IOL implantation in children has become popular
only within the past few years, and there is still a good deal to
be learned about how well it will work and how safe it will be over
a long lifetime. No serious or unexpected problems have been found
so far. The risk of a surgical complication that might harm the
child’s eye is slightly higher when an IOL is implanted.
A child who has cataract surgery now without an IOL may be able to
have one placed in the future with a second operation, but there
are some extra risks and disadvantages to secondary lens
implantation. A natural lens can accommodate to adjust the eye’s
focus from distance to near which of course an IOL cannot do.
Therefore is often necessary to provide the child who has had
cataract surgery with additional refractive correction for seeing
up close. This is usually done by means of bifocal or reading
glasses, which may be needed (with low power lenses) even if
contact lens wear or IOL implantation has been chosen. Sometimes,
for a particular child there is only one method of refractive
correction after cataract surgery that seems likely to work well.
In many cases, though, there is more than one good way to fill the
refractive need. The specific condition of the child’s eyes and
general health, and the specific concerns and wishes of the family
are very important in making the decision about whether glasses,
contact lenses, or IOL implantation should be used.
Copyright © 2013 Optical Training Institute – Irvine, California
5
Segment Heights
More on Strabismus
Strabismus (misaligned eyes). Amblyopia occurs most commonly with
misaligned or crossed eyes which is known as strabismus. The
crossed eye “turns off” to avoid double vision and the child uses
only the better eye. The eye that is not being used can eventually
lose its ablity to function and loss of vision can become
permanent.
Accommodative esotropia Accommodative esotropia occurs when there
is a significant amount of hyperopia in a young child. A child’s
crystalline lens is very flexible. So even though a significant
amount of hyperopia may be present, through accommodation, the
child can still produce enough plus power to bring the light to
focus on the retina. Normally, accommodation occurs to focus
objects for near vision tasks. However, when a child is farsighted,
or hyperopic, the lens must be used constantly. Associated with
accommodation, is convergence. The more we accommodate, the more
the eyes tend to converge. When there is a significant amount of
accommodation manifest in a young child, the eyes will tend to turn
in or “cross” creating a condition called esotropia. When the eyes
cross, the brain cannot fuse the two images it receives into one,
therefore the child sees two images, suffering from double vision
or diplopia. Since seeing two images is an intolerable condition,
the child suppresses vision in one of the eyes. When vision is
suppressed the eye can lose its ability to function, thus becoming
amblyopic.The figure on the
Copyright © 2013 Optical Training Institute – Irvine, California
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bottom of page 11 shows and infant with accommodative esotropia
with and without corrective lenses. Notice how the eyes become
properly aligned when the lenses are in place.
Plus powered spectacle lenses can be used to treat accommodative
esotropia. By placing a plus powered lens in front of the eye, all
or part of the hyperopia is corrected, minimizing the necessity for
the child to accommodate in order to bring vision into focus. This
resolves the problem of overconvergence as long as the lenses are
in place. When the lenses are removed, the eyes may cross
again.
Contact lenses can also work as well as glasses in the treatment of
accommodative esotropia. However they are generally more expensive
and demand more attention. Adolescents, are often willing to
undertake the responsibility for handling the contact lenses. Other
treatments may involve surgery to correct the unbalanced eye
muscles or to remove a cataract. Covering or patching the strong
eye to improve amblyopia is often necessary.
Esotropia Esotropia, is not necessarily accommodative. It can occur
when there is an imbalance in the tension of the extraocular
muscles which cause the eye to move in all directions and is the
most common type of strabismus in infants. In most cases, early
surgery can align the eyes. During surgery for esotropia, the
tension of the eye muscles in one or both eyes is adjusted. The
tight inner muscles may be removed from the wall of the eye and
placed further back on the eye. This adjustment weakens their pull
and allows the eyes to move outward. Sometimes the outer muscles
are tightened by shortening the muscle length to allow the eyes to
move outward.
Exotropia Exotropia, or an outward turning eye, is another common
type of strabismus. This occurs most often when a child is focusing
on distant objects. The exotropia may occur only from time to time,
particularly when a child is daydreaming, ill or tired. Parents
often notice that the child squints one eye in bright sunlight.
Although glasses, exercises or prisms may reduce or help control
the outward turning eye in some children, surgery is often
needed.
Strabismus Surgery The ophthalmologist makes a small incision in
the tissue covering the eye to reach the eye muscles. Certain
muscles are repositioned during the surgery, depending on which
direction the eye is turning. It may be necessary to perform
surgery on one or both eyes. When strabismus surgery is performed
on children, a general anesthetic is required. Local anesthesia is
an option for adults.
Recovery time is rapid. People are usually able to resume their
normal activities within a few days. After surgery, glasses or
prisms may be useful. In many cases, further surgery may be needed
at a later stage to keep the eyes straight.
For children with constant strabismus, early surgery offers the
best chance for the eyes to work well together. In general, it is
easier for children to undergo such surgery before school age. As
with any surgery, eye muscle surgery has certain risks. These
include infection, bleeding, excessive scarring and other rare
complications that can lead to loss of vison. Strabismuy surgery is
usually a safe and effective treatment for eye misalingment. It is
not, however a substistute for glasses or amblyopia therapy.
Copyright © 2013 Optical Training Institute – Irvine, California
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Ptosis
Ptosis is described as a drooping of the upper eyelid. The lid may
droop only slightly, or it may cover the pupil entirely. In some
cases, ptosis can restrict and even block normal vision. It can be
present in children, as well as adults, and is usually treated with
surgery. Ptosis can: Affect one or both eyelids
Be inherited
Be present at birth Occur later in life.
Ptosis which is present at birth is called congenital ptosis.If a
child is born with moderate to severe ptosis, treatment is
necessary to allow for normal vision development. If it is not
corrected, a condition called amblyopia (“lazy eye”) may develop.
If left untreated, amblyopia can lead to permanently poor vision.
Ptosis in children Ptosis which is present at birth is often caused
by poor development of the muscle which lifts the eyelid, called
the levator. Although it is usually an isolated problem, a child
born with ptosis may also have: Eye movement abnormalities
·Muscular diseases Lid tumors ·Neurological disorders Refractive
errors. Congenital ptosis usually does not improve with time
What are the signs and symptoms? The most obvious sign of ptosis in
children is the drooping lid itself. Children with ptosis often tip
their heads back into a chin-up position to see underneath their
eyelids, or they may raise their eyebrows in an attempt to lift up
the lids. Over many years, abnormal head positions may cause
deformities in the head and neck.
What problems can result from ptosis in children? The most serious
problem associated with childhood ptosis is amblyopia (“lazy eye”).
Amblyopia is poor vision in an eye that did not develop normal
sight during early childhood. This can occur if the lid is drooping
severely enough to block the child’s vision. More frequently, it
can occur
Pediatric ptosis patient before sugery
After sugery
Copyright © 2013 Optical Training Institute – Irvine, California
8
because ptosis tends to change the optics of the eye, causing
astigmatism. Finally, ptosis can hide misaligned or crossed eyes,
which can also cause amblyopia. If amblyopia is not treated early
in childhood, it persists throughout life.
How is congenital ptosis treated? In most cases, the treatment for
childhood ptosis is surgery, although there are a few rare
disorders which can be corrected with medications. In determining
whether or not surgery is necessary and what procedure is the most
appropriate, an ophthalmologist must consider a few important
factors: · The child’s age · Whether one or both eyelids are
involved · Measurement of the eyelid height · The eyelid’s lifting
and closing muscle strength · Observation of the eye’s
movements
During surgery the levators, or eyelid lifting muscles, are
tightened. In severe ptosis, when the levator is extremely weak,
the lid can be attached or suspended from under the eyebrow so that
the forehead muscles can do the lifting. Mild or moderate ptosis
usually does not require surgery early in life. Children with
ptosis, whether they have had surgery or not, should be examined
annually by an ophthalmologist for amblyopia, refractive disorders
and associated conditions. Even after surgery, focusing problems
can develop as the eyes grow and change shape.
Adult Ptosis The most common cause of ptosis in adults is the
separation of the levator muscle tendon from the eyelid. This
process may occur · As a result of aging · After cataract surgery
or other eye surgery · As a result of an injury · From restriction
of the levator, as may happen in the case of an eye tumor Adult
ptosis may also occur as a complication of other diseases involving
the levator muscle or its nerve supply, such as diabetes.
How is adult ptosis treated?s The ophthalmologist can provide a
comprehensive assessment of ptosis, a discussion of the available
treatment methods, and information about possible risks and
complications. Your ophthalmologist may use blood tests, X-rays or
other tests to determine the cause of the ptosis and plan the best
treatment. If treatment is necessary, it is usually surgical.
Sometimes a small tuck in the lifting muscle and eyelid can raise
the lid sufficiently. More severe ptosis requires reattachment and
strengthening of the levator muscle.
What are the risks of ptosis surgery? The risks of ptosis surgery
include infection, bleeding, and reduced vision, but these
complications occur very infrequently. Immediately after surgery,
you may find it difficult to completely close your eye, but this is
only temporary. Lubricant drops and ointment can be helpful during
this period. Although improvement of the lid height is usually
achieved, the eyelids may not appear perfectly symmetrical. In rare
cases, full eyelid movement does not return.
Summary Ptosis in both children and adults can be treated with
surgery to improve vision as well as cosmetic appearance. It is
very important that children with ptosis have regular ophthalmic
examinations early in life to protect them from the serious
consequences of untreated amblyopia.
Copyright © 2013 Optical Training Institute – Irvine, California
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Eye Safety for Children
Accidents resulting in eye injuries can happen to anyone. But in
fact, over half of the victims are under the age of 25. Many of
these injuries, over 100,000 annually, occur during sports or
recreational activities. Perhaps the most startling statistic of
all is that 90% of all eye injuries could have been prevented.
Parents are advised to acquaint themselves with potentially
dangerous situations at home and in school and to insist that their
children use protective eyewear when participating in sports or
other hazardous activities.
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Children and Sports Increasing numbers of children are
participating in sports at an early age. It is the responsibility
of the parents and coaches to provide protective eyewear and
enforce its use. Some sports in which children should be made to
use protective eyewear are:
· Baseball · Basketball · Racquetball · Tennis · Soccer · Hockey ·
Lacrosse
Contact lenses are not a form of eyewear protection and contact
lens wearers require additional protection when participating in
sports. In baseball, hockey, and lacrosse, a helmet with a
polycarbonate face mask or wire shield should always be worn. It is
important that hockey face masks be approved by the Hockey
Equipment Certification Council (HECC) or the Canadian Standards
Association (CSA). Sports goggles with polycarbonate lenses and
side shields should be worn when participating in basketball,
racquetball, tennis, and soccer. Choose goggles that have been
approved by the American Society of Testing and Materials (ASTM) or
pass the CSA racquetsport standard.
While skiing, protective glasses or goggles that filter out U.V.
and excessive sunlight exposure can be useful in shielding the eyes
from sunburn. Boxing poses an extremely high risk of serious and
even blinding eye injury. No adequate protection is available
although thumbless gloves may reduce the number of eye
injuries.
Parents of a child with permanently reduced vision in one eye
should carefully consider the risks of contact sports and injury to
the good eye before allowing their child to participate.
Eye safety at home and in the yard To provide the safest
environment for children:
Select games and toys that are appropriate for your child’s age and
responsibility level. · Provide adequate supervision and
instruction when your children are handling potentially dangerous
items, such as pencils, scissors and pen knives. Be aware that even
common household items such as paper clips, elastic cords, wire
coat hangers, rubber bands and fishhooks can cause serious eye
injury. Avoid projectile toys such as darts and bows and arrows. Do
not allow your children to play with air powered rifles, pellet
guns and BB guns. They are extremely dangerous and have been
reclassified as firearms and removed from toy departments. Keep all
chemicals and sprays out of reach of small children. Do not allow
children to ignite fireworks or stand near others who are doing so.
All fireworks are potentially dangerous for children of any age. ·
Do not allow children in the yard while a lawnmower is being
operated. Stones and debris thrown from moving blades can cause
severe eye injuries. Demonstrate the use of protective eyewear to
children by always wearing protective eyewear yourself while using
power tools, rotary mowers, line lawn trimmers or hammering on
metal.
Eye safety in school When participating in shop or some science
labs, students should wear protective goggles that meet the
American National Standards Institute (ANSI) Z87 safety code.
General eye safety for children Children with good vision in only
one eye should wear safety glasses to protect the good eye even if
they do not need glasses otherwise. These lenses should be made of
polycarbonate (an especially strong, shatterproof, lightweight
plastic) and be 3mm thick. Choosing a plastic or polycarbonate
frame will reduce the risk of injury from the frames themselves.
Frames which
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meet the ANSI standards offer the best available protection for
general spectacle wear. Prescription lenses can be fitted into some
types of sports goggles, but frames without any lenses do not
provide adequate protection.
When an injury does occur When an eye injury does occur, it is
always best to have an ophthalmologist (eye physician and surgeon),
or other medical doctor examine the eye as soon as possible. The
seriousness of an eye injury may not be immediately obvious.
Vision and Reading
The following are excerpts from an article on Vision, Learning and
Nutrition by Donald J. Getz, OD, FCOVD, FAAO It is reprinted by
premission of: www.children_special-needs.org
This article discusses children’s problems with reading, learning,
and behavior caused by convergence insufficiency, tracking
problems, esophoria, exophoria, and other visual problems.
Vision and Eyesight Eyesight is simply the ability to see something
clearly, the so-called 20/20 eyesight (as measured in a standard
eye examination with a Snellen chart). Vision goes beyond eyesight
and can best be defined as the understanding of what is seen.
Vision involves the ability to take incoming visual information,
process that information and obtain meaning from it.
Two general statements can be made about vision. First, vision is
learned. A child learns to see just like he learns to walk and
talk. When learning to walk and talk, he has the added opportunity
of imitating his parents and siblings. In addition, parents can
observe their children to determine if walking and talking are
developing properly. Vision development, however, generally
proceeds without much concerned awareness on the part of parents.
Because of these differences in development, no two people see
exactly alike.
Vision is learned; therefore vision is trainable. If a child does
not possess the necessary visual skills, he can be taught to
possess them through the proper vision therapy techniques.
Adequate Vision Is Critical to Learning Since something like 75% to
90% of all a child learns comes to him via the visual pathways, it
stands to reason that if there is any interference in those
pathways, a child will not develop to his maximum potential.
The Visual Skills Needed for Academic Success
Visual Acuity: There are many visual skills which are important for
academic success. One of the least important skills is termed
visual acuity (clarity, sharpness). This is the so-called 20/20,
20/400, etc., eyesight. All that is meant by the notation 20/20 is
that a person is capable of seeing clearly at a distance of twenty
feet. Unfortunately, how well a child sees at twenty feet has
little to do with how his vision functions at the reading and
learning distance — approximately eleven to sixteen inches from the
face. In fact, it is my opinion that the Snellen eye chart test
which measures visual acuity actually does more harm than good. It
gives both parents and teachers a false sense of security that
vision is normal. There are many other important visual skills that
might not be developed even though visual acuity at distance is
normal.
Copyright © 2013 Optical Training Institute – Irvine, California
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Binocular Coordination: One of the more important visual skills is
the ability to coordinate the two eyes together. A child is born
with two eyes, but he must learn to team them together. Some
children learn to do this properly while others do not. For
example, some children develop a problem known as exophoria, which
is a tendency for the eyes to deviate in an outward direction. This
is not the same as a condition known as exotropia where the eye
actually can be seen to be in an outward position.
Adequate Convergence: During the act of reading, the demand is for
the two eyes to turn inward so that they are aimed at the reading
task. If the eyes have a tendency to deviate outward, the child
must use excess effort and energy to maintain fixation on the
reading task. Most studies have shown that the greater the amount
of effort involved in reading, the lower will be the comprehension
and the lower will be the performance. When reading, the eyes do
not move smoothly over a line of print. Rather, they make a series
of fixations looking from word to word. When an exophoria exists,
each time fixation is broken and moved to the next word, the eyes
will tend to deviate outwards and they must be brought back in to
regain fixation. Human nature being what it is, the child generally
has an avoidance reaction to the reading task. This is compounded
by the fact that anything the child doesn’t do well, he would
rather not do. This is the child who looks out the window rather
than paying visual attention. He is commonly given labels. He is
often accused of having a short attention span and not trying. He
is told that he would do better if he tried harder, but he has
tried harder to no avail. He is often labeled as having dyslexia,
minimal brain dysfunction, learning disability, etc. Commonly, he
loses his place while reading and/or uses his finger or a marker to
maintain his place. While making the eye movements during the act
of reading, he might not land on the next word, but rather land a
few words further on. Consequently, he commonly omits small words
or confuses small words. Often, he just adds a word or two to make
the sentence make sense. If the two eyes are pointing at the same
point in space, a person will see the fixated object as being
single. Double vision or overlapping vision results if the two eyes
are not exactly pointing at the same point. Don’t expect a child to
tell you that his vision isn’t clear. He has no yardstick of
comparison to inform him that his vision differs from the vision of
anyone else.
Overlapping Vision
Vision and Reading (2)
Astigmatism, Eye-Hand Coordination, Visual-Motor Problems and more:
Children with coordination type visual problems can often be
spotted in a classroom. They get into distorted postures in an
attempt to get one eye out of the act. They often put their head
down on their arm, cover one eye with their palm or rotate their
head so that the bridge of their nose interferes with the vision
from one eye.
Esophoria: Another eye coordination problem is termed esophoria,
which is a tendency for the eyes to turn inwards. The educational
implication of this particular problem is that a child with
esophoria sees things smaller than what they actually are. In order
to see an object properly, it is necessary to make the object
larger. The only means at the disposal of the child to make it
larger is to bring it closer. Eventually, the child is observed
with his head buried in a book and still not achieving.
Copyright © 2013 Optical Training Institute – Irvine, California
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Reading Skills and Binocular Visual Skills One of the tests used in
optometric offices is to have the child read words while looking
into an instrument called a Telebinocular. The performance is
compared between reading with either eye alone and with both eyes
together. The difference in performance is often quite dramatic if
there is an eye teaming problem. One eye performance might be quite
satisfactory, but reading with both eyes together will be slower
and many more errors will be made.
Directionality Directionality is another visual skill important for
academic success. One test for this skill is illustrated in the
figure to the right.. Look at the figure and determine what you
see. If the visual reflex is from left to right, a duck will be
seen. However, if the visual reflex is from right to left, a rabbit
will be seen. This is just one test out of a series to determine
the directionality of the visual reflex.
It is a convention of our culture that the English language
proceeds in a left to right direction. Other languages proceed in a
right to left direction and still others have a vertical
orientation. Many people feel that it would make more sense if the
language proceeded as illustrated in the figure below. If a child
does not visually proceed from left to right, through vision
therapy he can be taught to develop this skill just like he can be
taught to team his eyes together.
Form Perception: Form perception is another important visual skill
for academic achievement. This can best be illustrated by referring
to Figure #7. The child is shown these forms one at a time and he
is simply asked to copy them. It is amazing to see some of the
distortions that a child will make in attempting to copy these
forms. If a child can’t perceive and copy these simple geometric
forms, it is unreasonable to assume that he will be able to
perceive the wiggly lines which make up letters which in turn make
up words, which in turn make up sentences which stand for abstract
ideas. We see children often who can’t tell the difference between
a square and a rectangle or a circle and an oval. This is also a
skill which can be improved through vision therapy.
Attention Span/Span of Perception: The Span of Perception is also
related to success in school. Many children see just one word at a
time with each eye fixation. Reading speed can be improved by
learning to see two, three, or more words with each eye fixation.
This could be compared to reading through a straw. This is
illustrated in Figure #8 below. It is easy to see the difference in
reading for meaning when the span of perception is wide.
Copyright © 2013 Optical Training Institute – Irvine, California
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Visualization: The ultimate visual skill is visualization. This is
similar to being able to see things in the mind’s eye. There are
authorities that state that the ability to visualize is very
closely allied to the ability to think. In other words, thinking is
related to the ability to abstract from specifics and the ability
to visualize is deeply involved in this process. Visualization is
also a trainable skill.
Kids and Contact Lenses
There are times when contact lenses may be the best option for your
youngest patients.
After all, contact lenses provide children many of the same optical
advantages as they do adults. These include better peripheral
vision, less distortion and less troublesome image size
differences. And contact lenses can eliminate the unwanted
prismatic effects of spectacles. Also, the hyperopic patient will
experience a decreased accommodative demand when using contact
lenses.
Here are some instances where contact lenses may be a viable option
for children.
1. Excessive Hyperopia, Myopia or Astigmatism A highly hyperopic
child often experiences considerable distortion and undesirable
prismatic seffects from high-plus spectacle lenses. This, in turn,
leads to compromised visual acuity and binocularity.
Further complicating the effects of spectacles is that the patient
rarely looks through the optical center. The weight of the
spectacle lenses often makes them slide down the small bridge of
the nose, forcing the child to view through the upper portion of
the lens. Also, active children often knock their frames out of
adjustment, so these kids are even less likely to view through the
center. Three things can greatly compromise cosmesis: magnification
of the eyes, the need for lenticularized lenses and difficulty in
maintaining a proper fit of the frame.Contact lenses can help
eliminate these problems and should be considered as a possible
option.
The highly myopic child also may have distortion, prismatic
effects, heavy lenses, poor fit and diminished cosmesis from
glasses. He or she experiences minification of images rather than
magnification. This minification can complicate a child’s ability
to adapt to spectacles, especially when reading. Again, contact
lenses can help eliminate these problems.
Children with high amounts of astigmatism experience similar
advantages from contact lenses as hyperopes and myopes, perhaps
more so because the distortion is worse for high astigmats who wear
spectacles. Again, contact lenses cause less disparity between a
patient’s eyes, both in cosmetic appearance and the image size the
child sees.
In some instances the child’s refractive status does not mandate
contact lens wear, but the lenses can dramatically improve his or
her performance at frequent activities. For example, a young
athlete may enjoy improved peripheral awareness while wearing
contact lenses rather than spectacles.
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Kids and Contact Lenses (2)
2. Anisometropia This is a special refractive condition for which
children may be fit with contact lenses. Again, spectacles may
cause distortion and prismatic effects for some young patients. The
anisometropic patient may also face some unique problems with
spectacles. Due to the dioptric difference between the two eyes,
spectacle correction often results in differing image sizes. This,
in turn, leads to spectacle-induced aniseikonia.
Ocular images that differ in size, clarity or luminance can
compromise fusion. Discomfort, suppression or poor stereopsis may
result. Once again, cosmesis is a factor because the patient’s eyes
appear to be different sizes.
Contact lenses help eliminate the differences between interocular
image sizes. They allow the patient to enjoy improved fusion,
visual development and stereopsis.
3. Aphakia Aphakia results when the crystalline lens is surgically
removed due to infantile cataracts, or other medical factor.
Depending upon the circumstances, either unilateral or bilateral
aphakia can exist . The resultant high hyperopia makes spectacles
extremely impractical for the infant. Aphakic patients require a
high prescription, and unless the child looks through the center of
the lenses, he or she will experience extreme distortion.
Some pediatric aphakes require a high plus in one lens but less
plus power in the other. The two eyes see different image sizes,
compromising visual development. Contact lenses can reduce that
problem, just as they would with another highly hyperopic
child.
4. Nystagmus When evaluating a nystagmoid patient, you need to
determine type of nystagmus, direction, frequency and whether the
nystagmus is dampened or eliminated in a particular gaze (null
point).
Sometimes you’ll find the null point, but the patient cannot take
advantage of it. Specifically, the null point may be outside the
optical center or perhaps the entire range of the spectacle lens.
This is an indicator that spectacles won’t work for that
patient.
Alternatively, contact lenses allow the patient to view objects in
the null point position and still benefit from refractive
correction.
Albinism and aniridia Patients with albinism or aniridia may
experience extreme glare, which results in reduced visual acuity. A
contact lens with a central tint and an opaque peripheral zone
would reduce glare and photophobia in these patients, thus
improving visual acuity. The former acts as a light filter, while
the latter creates an artificial pupil.
Corneal Injury Ocular injury can leave the corneal surface with
significant distortion, resulting in degraded retinal images. In
such instances RGP lenses can reestablish regularity to the eye’s
front refracting surface.
Children are just as vulnerable to corneal injury as adults.
However, some doctors hesitate to discuss contact lens options for
these children and simply prescribe glasses.
Copyright © 2013 Optical Training Institute – Irvine, California
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Amblyopia and Strabismus Many amblyopic and strabismic patients
have occlusion therapy to improve their visual acuity or
binocularity. While patching can be effective, children aren’t
always eager to comply. Discomfort or diminished cosmesis are often
the reasons. Even when a child wears a patch, we can’t always tell
whether the child is “peeking” around it, thus defeating the
purpose of this occlusion therapy. Occluder contact lenses can be
used, with opaque central regions of various sizes on such patients
The results: enhanced cosmesis, less self-consciousness and
increased compliance.