Anisometropia is a significant imbalance in refractive error between the eyes.
That is one of the eyes requires a significantly stronger corrective prescription in order to see clearly.
This is commonly found in Refractive Amblyopia, ie where one of the eyes is either not used fully compared to the other eye due to an excessively high prescription, or where one of the eyes appears initially to not function correctly.
Treatment for anisometropia is usually the corrective spectacle prescription to give maximal visual acuity for each eye. This is important to reduce the risk of Amblyopia in cases of untreated anisometropia. Vision Therapy may be useful in treating the effects of anisometropia.