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Is lazy eye genetic?

Samantha Barber

in Higher Education

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Bethany Evans on September 24, 2018

In the first place, let's be clear about the definition of "lazy eye". Many people who are untrained in the eyecare professions use this term loosely without really knowing what is what they are talking about. (This, with "pink eye" also, and this is my pet peeve, a topic for another day) That they think, mistakenly, that a fall of the eyelids (ptosis) is "lazy eye". However, other people mistakenly think that an imbalance in the extraocular muscles resulting in the eye turning (exotropia) or in (esotropia) is "lazy eye". The correct medical term for "lazy eye" is Amblyopia! This is defined as a decrease of the vision - sometimes very mild and sometimes serious - resulting in an eye that is not being used. Why is one eye not be used? Good question! Two main reasons: 1. the eye is misaligned, esotropia, exotropia, vertical tropia, or 2. the two eyes have a large difference in their refractive error, one eye may be +4.00 diopters hyperopia, and the other eye can only be +1.00 diopters vision of the future. If this child does not receive proper eyecare and forced to wear glasses, the +4.00 eye will almost certainly become Amblyopic. Remember, the brain has to accept the images of the 2 different eyes and then fuse those together to allow us to see in a single image. But, what if the right eye is the right and the left eye became 10 degrees? The brain receives 2 different images that are completely different and cannot fuse them together. So the natural response to double vision is to turn off or suppress the image from the eye that became. The suppression is also occurring in the +4.00 diopters of the eye in the previous example. The brain has a hard time merging the images of the +1.00 eye and +4.00 eye (which is blurry) so that only suppresses the +4.00 eye. Now you understand that the removal of the cause of the amblyopia, or "lazy eye". Back to the question: is lazy eye genetic? Amblyopia does not tend to occur in families, so that it is evident that there is a genetic component. However, it certainly is not the only determining factor. I see that many of the patients with amblyopia who have no family history. So there are environmental factors too.


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