Diplopia can be defined as:

Diplopia, commonly referred to as double vision, occurs when a person sees two images of a single object that should appear as one. This condition can arise from various issues affecting the ocular muscles, nerves, or the brain. When someone experiences diplopia, it may lead to challenges in depth perception and can significantly impair day-to-day activities. Understanding this term is crucial in the context of coding and clinical documentation, as recognizing diplopia helps in accurate diagnosis and treatment planning.

The other choices relate to different ocular conditions but do not accurately define diplopia. Inflammation of the eyelid edges refers to blepharitis, blurred vision can occur for many reasons including refractive errors or cataracts, while absence of the lens is referred to as aphakia. These terms are distinct and do not represent the phenomenon of seeing double, which is specifically what diplopia entails.