What does the term "double vision" refer to medically?

The term "double vision" refers to the condition known as diplopia. This phenomenon occurs when a person sees two images of a single object. The cause of diplopia can vary, ranging from issues with the eye muscles or their control, neurological conditions, to problems with the eye’s refractive components. When someone experiences diplopia, it can be a clear indication that there is a disruption in the visual pathways or muscular coordination that is normally required for proper binocular vision.

Monocular vision refers to the ability of one eye to see, and it does not imply seeing double images; hence, it is not associated with the concept of double vision. Exophoria is a type of eye alignment issue where one eye tends to drift outward, but this terminology does not directly describe the symptom of seeing two images. Astigmatism is a refractive error caused by an irregular shape of the cornea or lens that distorts vision, but it does not necessarily result in double vision; rather, it causes blurred vision. Therefore, the understanding that diplopia is the key term that accurately defines "double vision" is essential in differentiating it from other eye-related conditions.