Pediatric Vision Disorders - Optical Training

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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
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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.
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
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.
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
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.

Pediatric Vision Disorders - Optical Training

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