Common Causes and Misconceptions of “Lazy Eye”

First and foremost, let me unequivocally state that I hate the term “Lazy eye”. That term always sounded to me that if a patient just stopped being ‘lazy” they would see better. This is far from the truth.

“Lazy Eye” is the common name for a condition we call amblyopia which is a permanent decrease in the ability of a patient’s eye to see 20/20 vision, even with glasses or contacts. Amblyopia is caused by one of four conditions during childhood when the visual system is still developing.

Nutritional amblyopia occurs when a child is deficient in vitamin A consumption during gestation and childhood. Vitamin A is essential for proper retinal health and development. In the US we simply do not see nutritional amblyopia. It is an issue in third world countries but even with the challenges of poverty in America, children and expectant mothers do receive enough proper nutrition to prevent this from occurring.

The other three forms of amblyopia occur when the patient has a situation where one eye is not being utilized during childhood. A child’s visual system continues to form and improve from birth to roughly the age of 8-10. During this time if the eyes are being used equally, they will both develop the ability to see equally well. Once this time has passed, it is very difficult to undo the damage that has been done. During this time period, any blockage of vision to an eye, large unequal prescriptions, or eye turns can cause amblyopia to permanently occur.

All infants are screened at birth to make sure that they have not been born with congenital cataracts. A cataract is a clouding of the lens inside the eye. If a child has this at birth and it is not treated, then the quality of vision that this eye receives is poor and that eye will develop amblyopia. Luckily congenital cataracts are extremely rare and are dealt with surgically to avoid this from happening.

Our brains combine the images both eyes see and overlaps them to create what we sense as our vision. If one eye is extremely fuzzy due to a much larger prescription than the other eye, then the brain cannot overlap those two images. The brain is then forced to pick which eye to pay attention to. Since picking the fuzzy one would be silly, the brain chooses the clearer image and the other eye never becomes amblyopic due to non-use.

Similarly if the eyes are not both looking at the same target then the brain also has to make a choice. This is the condition that most people think of as “lazy eye”. Some people have muscle imbalances that cause one eye to turn inward or outward as they are looking straight ahead. If this happens only occasionally than no harm is done. However, when this turn is constant, the brain always sees one image from the straight eye and another completely different image from the turned eye. The brain then has the task of making sense of this. Since our eyes and nose both normally point in the same direction, our brain knows which eye is straight and which eye is not. The brain then ignores the turned image and this eye also becomes amblyopic.

Brookside Optometric looks for these conditions in every childhood exam we perform. If there is no history of “lazy eye” in the family, it is still important to have your child seen by age 5 to rule out this possibility. If there are family members that have had issues with “lazy eye” then we recommend that the child be seen at age 2. If amblyopia is detected then glasses and exercises can be prescribed to reverse any damage.

Finally, if you do have “lazy eye” please remember—you aren’t lazy; your eyes just aren’t equally efficient.