Sometimes even children with perfect eyes can’t see well. How can this be?
Practice makes perfect. Young eyes need practice in order for mature vision to develop in the brain. For this to happen, a clear image of the world needs to land on the retina and be transmitted to the visual cortex of the brain.
Amblyopia is the loss of vision caused when a clear image of the world is not available on the retina during key periods of development. The visual cortex of the brain develops dramatically in babies and young children. It continues to develop throughout the first decade of life.
Anything that interferes with a normal image on the retina during this time can lead to amblyopia – a loss of vision that continues even if no problem remains in the eye.
Amblyopia might occur in strabismus, when one eye deviates to the side and isn’t used as much. It might occur if there is unequal vision in the two eyes from astigmatism, or if one eye is more nearsighted or farsighted than the other. It might occur if there is a cataract blocking vision in one eye, or if there has been an injury.
Whatever the cause, if the “lazy” eye relaxes, the vision in that eye gets worse, and a destructive cycle begins. The initial difference between the eyes does not have to be dramatic.
Amblyopia can also occur if there is a severe blurring of vision in both eyes, as in severe nearsightedness or farsightedness.
Amblyopia only begins during the first ten years of life. It is more likely, and often more serious, the younger the child is when the retina is not receiving a clear image.
Most amblyopia is discovered during routine eye screening – without any symptoms having been noticed. The symptom of amblyopia is decreased visual acuity, but this is not usually found unless the child has her vision checked.
An eye that deviates, cloudiness in one eye, or any signs or symptoms of nearsightedness, farsightedness, or astigmatism might suggest that amblyopia is developing as a result.
If normal vision is not restored to the eye by about age 6, some degree of vision loss will probably be permanent. Usually a lazy eye should be diagnosed by age 3 in order to restore normal vision to that eye by age 6.
A March 2002 policy statement by the American Academy of Pediatrics (AAP) recommended that all babies have vision screening (including screening for strabismus and amblyopia) at the earliest possible age, and at regular intervals throughout childhood. In February 2011, the US Preventive Services Task Force (USPSTF) issued a recommendation for all children to receive vision screening at least once between 3 and 5 years of age.
In the AAP’s policy statement, the AAP discussed photoscreening, a test that can make checking vision easier and more accurate for even very young babies. Rather than relying on informal or subjective assessments of vision, a specially equipped camera takes their picture and a computer or a person analyzes the eye data obtained. Ask your pediatrician about having your baby screened.
If there are abnormal results on vision screening, or any reason to suspect amblyopia, the child should have a complete eye exam as soon as possible.
The key to treating amblyopia is starting early. The first order of business is to identify and plan to treat the underlying cause of the amblyopia if it is still present.
It is also important to temporarily block vision in the better eye so that the child will use and exercise the “lazy” eye. This process may go on for weeks or months or even years.
Eye patches have long been a standard treatment for amblyopia. But children and parents alike sometimes have a tough time following through. Even if the child is initially enthusiastic about looking like a pirate, the patch ordeal can soon get old. It did in my house.
I was pleased to see a study published in the March 2002 issue of Archives of Ophthalmology that tested children with amblyopia at 47 different clinical sites. Half received patching (6 hours a day for 6 months); the other half were treated with blurring eye drops in the good eye (one drop of atropine a day for 6 months).
Treatment was successful (at least 3 lines of vision improvement, or vision brought to at least 20/30) in 79 percent of the patched kids and 74 percent of those receiving drops. Atropine drops appear to be a great treatment choice for some families.
Corrective lenses may also be used in addition to eye patching or atropine for the treatment of amblyopia.
Amblyopia can be prevented by the early detection and treatment of strabismus, astigmatism, cataracts, and other vision problems.