Does covering one eye for an extended period of time increase the other eye's function? One of my friends recently told me he previously had lazy eye. He said the way he cured it was to cover his good eye with an eyepatch for about a week; this caused his other eye's muscles to strengthen by necessity. He also told me that his correction decreased slightly from the experience, because his eye had to compensate. I have found sources like these, though that effect seems temporary at best. This seems more like pseudoscience, and I don't consider it reputable. Is there any definitive evidence for or against this claim?

Assuming you are talking about what is commonly know as "lazy eye" or amblyopia from a medical standpoint, then **yes** patching the dominate eye is a common treatment that is used (see also, 1, 2, 3, 4). However, other treatments such as eye drops may be used to force the weaker eye to get stronger by blurring the vision in the dominate eye.

> When should patching be used for amblyopia treatment?
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> Patching should only be done if an ophthalmologist recommends it. An ophthalmologist should regularly check how the patch is affecting the child’s vision. Although it can be hard to do, patching usually works very well if started early enough and if the parents and child follow the patching instructions carefully. It is important to patch the dominant eye to allow the weak eye to get stronger. [See figure 2]
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> !Medical diagram of patched eye