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Pediatric Eye Care – Amblyopia

 

By Sandra M. Brown, M.D.

 

What Is Amblyopia?

Amblyopia is the medical term that describes poor vision in one eye from lack of use. This is the same as having an arm in a cast: while the cast is on, the arm muscles are not being used, and when the cast is removed the muscles are shrunken and weak.

 

What Causes Amblyopia? 

The brain decides not to use vision from one eye. Why would the brain do this?

  • Crossed eye or wandering eye: the brain shuts off the picture from one eye in order to avoid double vision.
  • Unequal focus: the brain shuts off information from the poorly focused eye to concentrate on the clear picture from the healthy eye. This unequal focus can be due to many reasons, including need for glasses, cataract, or injury to the eye.

When the brain always shuts off the picture from the same eye, that eye can develop amblyopia. Some children with crossed eyes will take turns using one eye and then the other eye. Because both eyes get used part of the time, amblyopia is less common. However, many children always have the same eye cross in, wander out, or turn up. In this case, it is always the same eye that is ignored by the brain. Even though the eye is not damaged, vision does not develop properly because the brain is not paying attention to signals from the eye that is sending the wrong picture. 

Each child's brain reacts to amblyopia treatment differently. Generally, the younger the child, the faster the amblyopia gets better. Amblyopia is very hard to treat after 5 years old. Strong treatment (such as patching almost full time) is used until the vision is as good as it will get. Sometimes it is not possible to get to normal vision, especially if the amblyopia was very bad to begin with. After this, maintenance patching is used (such as less than full time patching, or atropine) to hold the vision up. Patching time is usually slowly decreased. Regular visits are very important to be sure that vision is not sliding back to a poor level. Sometimes treatment is needed until 7 to 8 years old, when the brain "sets" the vision. Therefore it is very important for you to bring your child to all appointments and not "let time get away from you".
Most children's eye care specialists feel that treating amblyopia beyond age 10-11 years is not possible. This is because the brain gradually, but steadily, loses its ability to make new connections to the eye with amblyopia. Also, amblyopia caused by crossed or wandering eyes is usually harder to treat than amblyopia from improper focus. The very best time to treat amblyopia is as soon as it is detected. The younger the child, the more easily the brain increases the use of vision from the eye with amblyopia. Amblyopia treatment should never be "put off" until the child is older.

*** Critical Patching Concepts***

Amblyopia is often detected in children who are 2 to 3 years old. Kids at this age can easily take off their eye patches. They hate the patch because they understand perfectly well that it takes away the clear vision from the strong eye. The worse the amblyopia, the more your child will reject the patch. Tell yourself that patching is no different from any other "medicine." If your child needed an antibiotic, you would not allow him or her to spit the medicine out. In the same way, you must make your child understand that the patch is not optional. Your child cannot "decide" not to have patching treatment. Because patching only counts during the time the child is AWAKE, it is very important to follow the patching schedule and to keep a log. Most parents are patching less than they think!
Be sure you are putting the patch on the correct eye. Remember that YOUR RIGHT SIDE is the CHILD'S LEFT EYE when the child is facing you. If you are using adhesive patches, you may trim the adhesive part to fit so that there are no loose edges that the child can use to pull off the patch, but make sure the patch completely covers the eye so that the child cannot peek out. Watch your child very carefully to see if he turns his head to the side when wearing the patch - it probably means that he has made a peek-hole and is looking through it instead of using the eye with amblyopia.
If your child is patching less than full time, you can divide the patching to fit your schedule. However, it is best to patch at least 2 hours at a time. Surprisingly, many children patch better at school and day-care than at home. Dropping the child off wearing the patch is a good approach. The school then takes the patch off after the specified amount of time has passed. Be sure to leave some spare patches with the responsible adults.
Children with very poor vision in the eye with amblyopia will often want to stay close to you initially. They may not want to play outside, or may act frightened in strange places. Their coordination may be very poor, and they may drop toys and fall more frequently. As the vision improves, the child will behave more normally. This is an excellent sign, and it is one way you can follow the success of your treatment between doctor visits.
Obtain a skin preparation called benzoin at the drugstore, usually near the area where the athletic bandages are. This is a strong-smelling brown liquid. Put it on your child's skin on the cheek, nose, and over the brow where the adhesive from the patch will be. You can use a cotton ball, a washcloth, or your fingertip to do this. Allow the benzoin to dry for one minute, then apply the patch. This really helps to keep patches on in active children. A cheaper alternative which works with some kids is to use a liquid antacid such as Maalox or Mylanta, in the same way that you use benzoin.
For younger children, make elbow splints by using toilet-paper cardboard, paper-towel cardboard, or potato chip cans with the metal rims cut off (Pringles). Slide the splints over the child's arms to cover the elbows and tape them into place above and below with bandage tape. This will keep the child from bending his arms to reach the patch. Generally it takes only one or two times in splints before the child learns to leave the patch alone. Please closely supervise your child during this time to prevent an accident such as falling down the stairs. The shirt straight jacket involves taking an adult-size button down shirt and putting in on the child backwards, buttoning it up fully from hem to neck. The sleeves will hang down far past the child's hands. Pin the sleeve ends to the child's pantlegs. Please closely supervise your child during this time to prevent an accident.
Many children get a rash from the adhesive on the patches. Often this is a mild rash that goes away overnight. If your child's skin is getting quite raw, pick up a tube of over-the-counter hydrocortisone cream in the mildest strength. Rub it on to the rash area at bedtime. Usually it takes only 1 to 2 doses per week to keep the rash under control.
A little atropine goes a long way. Generally the dose is one drop to the good eye every morning. Atropine will make the child's pupil dilate, and the pupil will stay dilated overnight. However, you still need to use the medication daily unless instructed to use it less often. It is very important to blot up any drips on the child's face and to prevent him from rubbing the good eye (that just got the atropine drop) and then rubbing the eye with amblyopia. This treatment won't work if the atropine is affecting both eyes! Also, be sure to wash your hands promptly. Several moms have gotten atropine in their eyes by putting on eye makeup. They didn't like it!
Use plain brown patches for 2-3 days. If the child patches consistently without fussing, reward him/her with a colored and decorated patch (available in our Optical Shop). Make a daisy chain from construction paper. Make every third or fourth link a different color. After each day of good patching, the child can remove one link. When the colored link is reached, give a reward! Parents...Don't forget to reward yourselves too! Again, please remember that amblyopia therapy is an important part of your child's overall treatment and the method and schedule prescribed by Dr. Brown should be followed as closely as possible. If you have any questions or concerns regarding your child's eye care at any time, please do not hesitate to call our office.

Treatment of Amblyopia

The first step in amblyopia due to poor focus is to improve the focus. This usually means glasses. If there is something blocking the proper focus of light, such as a cataract, then surgery may be needed. In children with crossed or wandering eyes, glasses are frequently helpful as well. Sometimes the problem is due to poor focus and crossing at the same time. A small number of children improve with glasses alone. Most children require some treatment that forces the brain to use the eye with amblyopia instead of the strong eye.

Blocking light from entering the eye. The best way to force the brain to use the eye with amblyopia is to block light from entering the strong eye. There are several options:

  1. Adhesive skin patch. These are basically egg-shaped bandaids. They are available in our Optical Shop. You can also buy these patches at drugstores and in supermarkets. If the child has glasses, the patch is put on the skin and then the glasses are put on over the top. The advantage of skin patching is that it is very difficult for the child to peek (cheat) around the patch. The disadvantage is that in hot weather the patches tend to sweat off, and some children develop a rash to the adhesive. If a rash develops, it can usually be easily treated by rubbing over-the-counter hydrocortisone onto the skin at bedtime as needed. Some parents substitute the jumbo size "Knee bandaids" which will also work if they stay on.
  2. Patch-Works patch. This is a cloth patch that fits over the glasses. These are available in our Optical Shop. The advantage is that there are no problems with patch rash or the patch coming off the skin. The disadvantage is that it is slightly easier to peek around the cloth patch. If your child pulls his glasses down to avoid the patch, the treatment will not work.

    Pirate patches are NOT recommended as it is too easy for children to peek around them.

  3. Opaque Contact Lens. In special circumstances the child can be fitted with a special soft contact lens which has been dyed black. This contact must be inserted and removed daily. For older children who are in school all day, the opaque contact lens can be an excellent treatment because it is just as effective as skin patching (blocks all light) but it is almost unnoticeable to others (especially in dark-eyed children). Unlike the other treatments listed, the opaque contact lens does place the good eye at very slight risk for injury from infection or corneal scratches.

Blurring light that enters the eye. This is another alternative in children with milder amblyopia. These are not "fast" treatments. They can be useful for maintenance treatment after maximum improvement in vision has occurred using stronger methods.

  1. Contact Paper. Clear contact paper can be put on the inside of the eyeglass lens in front of the strong eye, which significantly blurs the vision. Another person standing only a few feet away from the child might not notice the contact paper at all or might think the lens was slightly dirty. This is a good treatment for older children who are shy about wearing a patch in public. It is not a good treatment for younger children who will pull down their glasses or take them off to avoid the blurry contact paper.

    A Good Tip from a Parent: the contact paper can be removed and stuck to the refrigerator, and then reused for several days.

  2. Atropine: Atropine is an eye drop or ointment that blurs vision in farsighted children. It is put into the strong eye once a day in the morning. In some kids, the glasses lens in front of the strong eye is changed to plain glass. Atropine can be easier than patching, but it doesn't work in children with very bad amblyopia. Atropine is sometimes used in combination with patching for kids who cannot be closely watched all day. Atropine has rare side effects such as sleepiness, crankiness, flushing of the face, and stomach aches or change in potty habits. These typically occur only in younger children. If Dr. Brown prescribes atropine for your child and you think side effects are happening (it usually takes 2-3 days of eye drops before side effects start) please stop the atropine and call the office. 

 

Copyright Sandra M. Brown MD, March 28, 2005