What term describes the difference in visual acuity between the two eyes?

The term that describes the difference in visual acuity between the two eyes is amblyopia. Amblyopia, often referred to as "lazy eye," is a condition where one eye has reduced vision that cannot be fully corrected with glasses or contact lenses and is usually a result of poor or abnormal visual development during childhood. This difference can stem from various issues such as strabismus (misalignment of the eyes), refractive errors, or other conditions that prevent the eyes from working together effectively.

The other options pertain to different concepts related to eye health and function. An afferent pupillary defect indicates an issue with the optic nerve or severe retinal disease, while a tonic pupil is a condition characterized by a dilated pupil that reacts slowly to light. The swinging flashlight test is a clinical test used to determine the presence of a relative afferent pupillary defect, but it does not describe visual acuity differences between the eyes. Thus, amblyopia is the only option that specifically refers to a disparity in visual acuity.