Amblyopia is generally known as ‘lazy eye’. Amblyopia is decreased vision in one or both eyes due to abnormal development of vision in infancy or childhood. Problems with the eyes may not be obvious in children with amblyopia. Vision loss occurs because the brain is not properly stimulated by the blurred image it receives from the eye. The brain “learns” to see only blurry images with the amblyopic eye even when glasses are used. As a result, the brain favors one eye, usually due to poor vision in the other eye. Amblyopia is the leading cause of vision loss among children. Treatment of the condition becomes difficult and can result in incomplete restoration of vision if treated after age six. Children with amblyopia often develop low self-esteem and reading difficulties and permanent vision impairment can result in fewer career options in the future.
In many cases the conditions associated with amblyopia may be inherited.
The most common causes of amblyopia are:
- Unequal focus and refractive errors: Amblyopia occurs when one eye is out of focus because it has a higher refractive error than the other eye. Refractive errors are eye conditions that are corrected by wearing eyeglasses (nearsightedness, farsightedness or astigmatism). The unfocused (blurred) eye is “turned off” and becomes amblyopic, but may look normal. As a result, the detection of this type of amblyopia can be delayed significantly. This is especially common if screening or testing for vision problems is not done in a timely fashion, before a child starts school.
- Strabismus (misaligned eyes): Amblyopia occurs most commonly with misaligned or crossed eyes. The crossed eye is suppressed or “turned off” to avoid double vision, eventually resulting in loss of vision in that eye. The child then uses only the better eye. Children with mothers that smoke and use drugs or alcohol have a higher risk for amblyopia and strabismus.
- Cloudiness in the normally clear eye tissues: Any structures that prevent a clear image from being focused inside the eye can lead to the development of amblyopia in a child i.e. scars at the surface of the eye due to infection or an accident, lid malformations or an eye disease such as a cataract (clouding of the eye’s naturally clear lens) to name a few.
Amblyopia becomes difficult to treat when detected after age six. Late diagnosis and treatment with patching and glasses will improve the vision but not restore it to the normal visual potential. The younger the child is detected with amblyopia and treated, the easier it is to fully reverse the condition. Untreated amblyopia will lead to very poor vision and the loss of the ability to perceive depth.
To treat amblyopia, your child might need to wear glasses and patch the stronger eye to be able to use the eye with weaker vision. This will encourage the brain to use the weaker eye.
Patching: An adhesive patch is worn over the stronger eye. Patching stimulates vision in the weaker eye and helps parts of the brain involved in vision develop more completely. Duration of this treatment method varies, however the younger the child, the quicker the vision will improve.
Eye drops: A drop of a drug called atropine is placed in the stronger eye to temporarily blur vision. This is another method to treat the lazy eye
Once optimal vision has been reached, many children will need some form of a maintenance treatment until their visual system has reached maturity.
Vision screening is a short test that can indicate the presence of a vision problem or a potential vision problem. Vision screening cannot provide a prescription for glasses; instead it can indicate that a child requires a more detailed examination with an eye doctor (optometrist).
Optometrists will administer special eye drops that will dilate your child’s pupils so that they can take a closer look at the eyes. Vision screening is recommended by the Canadian Pediatric Society (CPS) and the American Academy of Pediatrics (AAP) to detect amblyopia early enough to allow successful treatment.
What are the challenges in detecting vision problems in young children?
- The majority of eye conditions in children typically start to affect vision in children 18 months to 5 years.
- Preschoolers are not always verbal; they are often unable to tell you if their vision is blurry.
- Preschoolers might not be cooperative in a traditional eye examination setting (using charts etc.)
Parents can help identify potential vision problems by watching for the following signs in their children:
- Sitting close to the TV
- Holding a book too close
- Tilting their head
- Frequently rubbing eyes
- Has a short attention span for the child's age
- Has an eye that turns in or out
- Is sensitive to light
- Has difficulty with eye-hand-body coordination when playing ball
- Avoids coloring activities, puzzles and other detailed activities