Amblyopia
Most of the population is unfamiliar with the term “amblyopia,” and I can definitely see why; there is no obvious indication from the word to lead us to its definition, at least none that the world would be commonly familiar with.
As a technical term, we ophthalmologists use amblyopia to mean a problem with vision related to its connection to the brain. The most common circumstance that we encounter this is in a child who can achieve better vision in one eye compared to the other. When this happens, the visual input from the eye to the brain in the worse eye is relatively absent, and the development of the connection between the worse eye and the brain does not develop normally. Early on, this can be improved by improving the visual input from the eye, often by the use of glasses. If that visual input is improved, the eye-brain connection can normalize. However, if nothing is done to improve the visual input by a critical age, the eye-brain connection will forever remain abnormal, and the vision can never really be normalized. At that point, we say that amblyopia has set in forever.