Active Vision therapy for Amblyopia

Active Vision Therapy

Introduction

In all branches of medical science, there is now great emphasis not only on early diagnosis and treatment of all disorders and diseases but also on measures that aim at their prevention.

However, squint in children with its associated loss of normal binocular vision, and frequently with the loss of useful vision in one eye due to amblyopia (lazy eye) if early treatment is not undertaken, has till now been much neglected mainly because of an inadequate appreciation of simple principles relating to its investigations and treatment.

Doctors in general and the lay public in particular have been ignorant about the various grades of vision, e.g. Simultaneous perception, fusion and stereopsis and not much interest has been shown to understand the importance of binocular vision and depth perception.

This paper is designed to present a simple approach to the subject of binocular vision, like 3-D perceptions, squint, amblyopia and their understanding by the patients, parents and the general doctors.

Binocular single vision (BSV) is one of the most important features of the human race that has bestowed upon it the supremacy over the rest of the animal kingdom.

It is not without reason that about 60% of the brain tissue and more than half of the twelve cranial nerves serve the eyes.

This binocular single vision is accomplished by a perfect coordination of the two eyes both at rest and movement. The two ?dimensional images of an object of interest formed at the fovea of each eye is processed and perceived in the brain as one three dimensional (3-D) image. This requires constant and controlled activity of the appropriate eye muscles to maintain fixation of the two eye-cameras on the concerned object, irrespective of the movement between it and the observer. It also requires the accommodational or focusing mechanism to maintain clear view even as the object moves closer or farther.

The basic aims in the treatment and care of children with eye muscles problems and lazy eyes (amblyopia) are:

1. Good vision in each eye.
2. Eyes that appear cosmetically straight.
3. Eyes that sees straight (Eyes that work together as a team).
4. Stereopsis (3-D Vision) or depth perception.

The course of treatment includes the following singly or in combination:

• Glasses
• Eye drops or ointment
• Patching
• Surgery
• Orthoptic training
• Pleoptics and active vision therapy

Your eye surgeon will decide the best course of treatment suitable for your child. His orthoptist will try to educate or re-educate the two eyes to work together by breaking down the faulty visual habits and attempting to establish correct ones.

Our experience has been that the quality of results improves in direct proportion to the effort put into the orthoptic training and active vision therapy. My attitude towards the value of these visual training methods has been influenced by the efforts of my team and the children themselves who come to us for treatment.

The significance of this new field to the parents and to the child specialist is that the vision of the child with or without squint can usually be improved if treatment is begun at a very early age.

In eye practice, the most common problems are related to problems of binocular vision and ocular motility. According to reliable estimates, about 2% of the children of our country have crossed eyes. The majority of them, it is hoped are receiving treatment of one kind or the other.

The parents of the child with crossed eyes are naturally upset and worried over their child and many questions about the problem arise in their minds. The successful treatment of squint and amblyopia demands the closest cooperation between the parents and the eye surgeon. Often the eye surgeon is so busy that he does not have the time to explain the condition properly to the parents. Frequently the parents cannot fully understand such an explanation if it is given in its entirety at a single visit to the doctor’s office. The bite would be too big to chew.

Doctors in other branches of medicine other than that of the diseases of the eyes have little reason to learn about crossed eyes in any great detail. They are too busy keeping up with the advances of science in their own particular fields of interest and hence may find information of interest in these pages -information which may enable them to give sound advice on the subject when consulted by the parents of the child with crossed eyes.

This paper is written primarily for the parents, however. It is hoped that it will answer the majority of their questions- questions that they are sure to have. As a result, they can better cooperate with their eye surgeon in his treatment of their child. There are few conditions in the field of medicine that demand greater cooperation between parents and physician than the care of the child with crossed eyes with or without the presence of amblyopia (Lazy eyes). If the results of the treatment in but a single case can be improved upon, then this would not have been written in vain.

Teamwork of the Two Eyes

In order to understand the problems of eyes that cross, we must know some basic facts about eyes that that are not crossed.

Co-ordination of the Two Eyes

The fact that we have two eyes is so taken for granted that the eyes are rarely given a thought unless something happens to one of them. For most purposes, our two eyes work together as a team so smoothly that we are not conscious of either eye separately unless, for example, we get a foreign body in one. Anybody who has been forced to wear a patch over one eye for a day or so, whatever the reason, can recall the difficulty encountered in performing the simplest acts-even going up or down the steps or walking through a narrow doorway. A person who is accustomed to having the use of two normal eyes which work together properly and who is suddenly deprived of the use of one of them, even temporarily, is in a sad fix indeed. Before considering this sudden helplessness, which descends upon us with the temporary loss of the use of one eye, let us first consider the mechanism whereby the two eyes work together.

Suppose you are walking along the street and suddenly decide to look to the right. You have no sooner made this decision than you have done just that- looked to the right-and done it almost instantly. Did you ever stop to think of the remarkable thing you have done? Or of what a marvelous mechanism is called into play so that you could see to the right? Probably not, because you have been able to look to the right or to the left or in any other direction you choose for as long as you as remember. Let us see how you do it.

What Makes the Eye Move?

Moving the eyes requires a chain of command exactly like that used in the army.

The Eyes As A Team

You can roll your eyes in any direction. Did you ever stop to wonder just how you do it? It is much easier to do it than to explain it, as a matter of fact. The eyes are moved by muscles in much the same way that you use rein to pull on the horse’s head. If you want to turn to the right, you pull on the rein running to the right side of the head; if you want to turn to the left, you pull on the rein on the left side of his head. If you can imagine a horse with three reins running on each side of his head instead of just one rein, you will have a fairly good picture of the muscles that move the eye. Our horse would have a total of six reins by which we might direct his head movements and thus guide him. There are six muscles that run the eye ball, like reins to our horse’s head, that move the eye.

Fusion

We have so far discussed only the movements of two eyes and how they move together. Our eyes would be of little value to us if they only moved. They must see, and if our eyes are working normally, both of them must look at the same thing at the same time. This means that the lines of vision of the two eyes must always meet at whatever object we wish to inspect. It is just as if we have two cameras and wanted to take a picture of the same object with each camera at the same time and have the pictures so much alike that we could hardly tell one from the other. This is what actually happens because each of our eyes is merely a camera.

Suppose you look at a tree. Your right eye takes a picture of the tree and sends it to your brain. Your left eye also takes a picture of the same tree and sends it to your brain. The brain receives two separate pictures or images of the same tree-one from each eye. If you are to keep from seeing two trees when there is in reality only one tree, then the brain must put the two pictures together and make a single picture of them. This is done and the process of fusing the two pictures into a single picture is known as fusion.

If your brain could not fuse separate pictures of the same object coming to it from the two eyes, then you would see two of everything – you would see double. This would be annoying, of course, but it could be even worse if you decided to climb a tree! Obviously there is only one tree there, but if you saw two trees, you could not tell which was the real tree that could be climbed and which was merely the image or picture of a tree that wasn’t there at all. In short, you would be unable to place objects in the world around you accurately in space where they belong if it were not for the process of fusion.

The ability of the brain to fuse images of objects seen by the two eyes separately is something that develops after birth. A baby is born with two eyes and two legs. He can move his legs and he can move his eyes, but in neither instance can he move them accurately together in coordinated movements. He cannot walk and he cannot fuse! He makes many movements with his legs as if he might walk, but he cannot walk until he has learned to do so. He may at first learn to stand alone, then to toddle perilously about, and finally to walk gracefully and well. In the same way, the eyes make many movements at birth, but these movements are not always made together. Later the eyes begin to move together fairly well, and finally the brain learns to fuse images of objects seen by the child’s two eyes quite accurately. As the child finally learns to walk, so he finally learns to fuse, although he can do neither at birth. Both walking and fusing must develop, and to a certain degree be learned. A child learns to walk by using his legs together as a team, and he learns to fuse by using his two eyes together as a team. The average child can both walk and fuse at the age of 1 year but he can do neither as well as he will be able to do at an older age. The child usually learns to fuse accurately and well at about the age of 5 1/2 to 6 years. Once fusion is well developed, it helps the brain centers to control movements of the two eyes together with even greater coordination than is possible without fusion.

Fusion has developed comparatively recently in the evolution of man. As with any other recently developed faculty, in the case of fusion, a disturbance of function is more easily produced and abnormalities are much more common. Some children are born virtually without the fusion faculty, but since it is a common denominator for the success in the treatment of squint and lazy eyes (amblyopia), we must look carefully for any trace of it and develop it if it is rudimentary.

Fusion Helps Control Eye Movements

If you are about to cross a street and you hear an automobile horn blow suddenly on one side of you, you immediately look to that side. When you decided to look in that direction, you did not know exactly where the automobile was except that it was on one side. You therefore started your eyes moving toward that side until the auto came into view in the corner of one or perhaps both eyes. Once you have located the auto, even out the corners of your eyes, both eyes turn immediately to look straight at it. Once the auto was seen out of the corners of your eyes, the process of fusion was largely responsible for sending other messages to the brain to tell it exactly how far to move the eyes before stopping them. Thus it is that you may move your eyes, even when they are not closed, but when you open them and begin looking at objects around you, the process of fusion plays an important part in telling the brain just how far to move the eyes and in what position to stop them in order that you may see objects that you want to see and what is more important-that you may see only one of the particular object instead of seeing it doubled. Fusion is the magic cement that binds together the lines of vision and keeps them parallel.

Depth Perception

We have said that looking at an object with our two eyes is like taking a picture of the same object at the same time with two cameras placed side by side in such a manner that the two pictures taken are almost identical. No matter how closely together we may place the two cameras, however, the pictures that they take will never be exactly identical because each camera would be taking its picture from a slightly different angle or view than the other camera. In the same way, the images of the objects in the world around us that are formed in our two eyes and sent to the brain to be fused are not exactly alike, because each eye sees things from a slightly different position in the head. The brain, however, handles this slight difference in the two images that it receives and fuses very nicely and even gets information about how far away the object is located from the eyes. In other words, we have depth perception partly because our two eyes never see the same object from exactly the same position and thus each eye sends a slightly different picture of the object to the brain to be fused.

The outfielder in the cricket game needs good depth perception in order that he may correctly judge the ball and position himself at the point where the ball will fall to the ground in order to catch it. If you do not think this requires good depth perception and the use of the two eyes, have a friend throw a ball to you and try to catch it with one eye closed. You will find it very difficult, if you can do it at all. Or try playing a game of tennis or badminton with one eye closed and see how well you do it. You will be lucky to hit the ball or the shuttle cock at all.

You use depth perception when driving your car along a highway, particularly in passing another car on a busy road. You must judge the speed of the car ahead of you, but this is usually easy because your speedometer tells you how fast you are driving. The hard part is to judge the speed of cars traveling towards you in order to decide whether or not you have time to pass the car ahead of you before the other cars coming toward you get there.

You even use depth perception in eating a meal when you reach for objects on the table which are located at varying distances from you.

The preceding discussion does not mean that a person with only one eye has absolutely no depth perception at all because this is not true. There are other clues to depth perception beside the slight difference in the images of objects seen by the two eyes and sent to the brain. Shadows, color haze, and the known comparative size of other objects all help the one eyed person in attaining some degree of depth perception. However a one eyed person can never have as keen depth perception as a person with two eyes functioning normally together as a team.

Fusion with good depth perception is, therefore, the ideal goal in the treatment of crossed eyes, although it is not always possible to attain it for one reason or another.

Why Do a Child’s Eyes Cross?

There are numerous questions that occur in the parents when it is first recognized that the child’s eyes are not straight. A sincere attempt is made through this book to answer the majority of these questions.

To the question, why are my child’s eyes turned? We know several immediate causes but only a few of the underlying ones. Honest parents will often ask themselves; is it our fault that our child’s eyes are turned, and is there anything we could have done about it. The correct answer to this question is usually “Yes” to the first part and “No” to the second. Barring accident, injury, or disease, turned eyes are known to run in families. Thus there is fairly good evidence to show that children inherit certain factors from their parents which may result in crossed eyes. There is, however, nothing the parents could have done about such a familial trend. It is a well known fact that all the members of a family need not necessarily show same family characteristic in order to pass it on to other members of the same family in the next generation. Thus a mother and father with perfectly normal and straight eyes may have relatives with crossed eyes, and these normal appearing parents may have one or more crossed-eyed children. The pattern of heredity seem strange indeed to the average person who has not, like the geneticist ,spent a lifetime studying such problems.

Squint is a term that covers all the conditions in which the two eyes are not properly aligned. The types of squint vary in degree. Some children have eyes that are straight most of the time-rarely turning in or out. In such a situation, the condition is called intermittent squint. The degree of turning or angle of squint is a matter of importance both from cosmetic and medical point of view. Oftentimes a squint of a very small angle is harder to treat successfully than a large-angle squint.

Child Symptom Checklist

Has your child ever reported or have you or anyone else noticed any of the following?

• Unusual blinking or eye rubbing
• Eyes feel dry
• Watering, dry or bloodshot eyes
• Eye turns in or out
• Squints, closes or covers one eye when reading
• Head too close to paper when reading or writing (only 7 or 8 inches)
• Unusual posture / head tilt when reading or writing
• Skips lines or loses place when reading or copying
• Skips, rereads or omits words
• Poor reading comprehension
• Confuses or reverses letters, numbers or words
• Confuses right and left directions
• Makes errors copying
• Writing is crooked or poorly spaced
• Misaligns letters or numbers
• Avoids near tasks such as reading
• Dislikes tasks requiring sustained concentration
• Poor spelling
• Must “feel” things to “see” them
• Carsickness
• Headaches or dizziness after intense visual activities such as reading or computer work
• Blurred vision, distance or near, at any time
• Double vision
• Eyes hurt or tired after close work
• Letters or lines “run together” or words “jump” when reading
• Eyes bothered by light
• Sees flashes of light
• Sees more clearly with one eye than the other
• Loss of field of vision missing in one or both eyes
• While reading, sees the print move or go in or out of focus
• Reads very slowly
• Uses a finger or marker to keep place while reading or writing
• Has difficulty remembering what they have read
• Mind wanders while reading
• Feels sleepy while reading
• Restless when working at a desk
• Feels unusually tired after completing a visual task
• When concentrating, tends to loose awareness of surroundings
• Difficulty tracking moving objects, balls, etc.
• Unusual clumsiness, poor coordination
• Difficulty with eye/hand coordination in sports such as badminton,cricket, etc.

Share on Facebook

Tweet

Follow us

Save