What does diplopia mean?
Diplopia, known in everyday language as double vision, is the condition in which a person perceives a single object as two images. It arises when the eyes fail to align properly or when the nerves or brain areas controlling eye movement are impaired, though causes within the eye itself can also produce it. Clinicians classify diplopia as binocular, when it vanishes upon covering either eye, or monocular, when it persists, a distinction that helps pinpoint the underlying problem. The word comes from the Greek diploos, meaning 'double', combined with ops, 'eye', making its construction transparently descriptive. Because sudden-onset diplopia can indicate serious conditions such as stroke, nerve palsy, or raised intracranial pressure, it is treated as a symptom warranting prompt medical evaluation rather than a mere inconvenience. While primarily a technical term of medicine and optometry, it appears regularly in health writing and patient accounts, and understanding it equips readers to describe a potentially significant symptom precisely.
nounDouble vision, the simultaneous perception of two images of a single object, usually caused by a disorder of the eye muscles, nerves, or brain.
- A medical condition in which a single object appears as two images, typically resulting from misalignment of the eyes or neurological dysfunction.
"After the concussion, she experienced persistent diplopia and was referred to a neurologist."
"The stroke left him with horizontal diplopia that slowly improved over several months."
"Monocular diplopia, in which doubling persists even with one eye closed, often points to a problem within the eye itself rather than the nerves."
Rarely used in the plural; the noun is normally treated as uncountable, referring to the condition generally rather than to countable instances.
"Transient diplopias were reported among patients with vestibular disorders."
The word literally means 'double eye' in Greek — and it's why you should never ignore suddenly seeing two of everything, because it can signal something seriously wrong in your brain.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of diplopia
Diplopia derives from the ancient Greek diploos, meaning 'double' or 'twofold', combined with ops, meaning 'eye', via New Latin. The same Greek root diplo- appears in modern scientific terms such as diploid and diplococcus. The word entered English through medical Latin, becoming established in ophthalmological vocabulary during the nineteenth century as clinical descriptions of vision disorders became standardized.
Related word forms
How diplopia is actually used
Diplopia is a formal clinical term used almost exclusively in medical and ophthalmological contexts; everyday speakers say 'double vision'. It is classified clinically by whether it disappears when either eye is covered (binocular) or persists (monocular), which helps localize the underlying cause.
Easily confused with diplopia
Myopia is nearsightedness, where distant objects appear blurred, whereas diplopia is seeing one object as two distinct images.
Amblyopia ('lazy eye') is reduced vision in an eye due to abnormal visual development, while diplopia is the perception of double images.