13th February 2025

Overview of diplopia

Diplopia, or double vision, is the separation of images horizontally, vertically or obliquely.

Diplopia can be monocular whereby the abnormality persists when the unaffected eye is closed. This is typically associated with local ocular causes such as refractive error or media abnormalities.

Binocular diplopia is the result of dysfunction of the extraocular muscles which leads to ocular misalignment, preventing fusion of the two images produced by each eye. The aetiology of binocular diplopia can be classified according to the segment of the efferent oculomotor pathway that is involved.

The following will be discussed:

Location				Example
		Supranuclear		Progressive supranuclear palsy
		Nuclear and internuclear		Internuclear ophthalmoplegia
		Infranuclear	Cranial nerves	Third nerve palsy Fourth nerve palsy Sixth nerve palsy
			Muscles and neuromuscular junction	Myasthenia gravis Thyroid eye disease Miller Fisher syndrome

Table 5 Causes of binocular diplopia

Figure adapted from icons through The Noun Project, CC BY 3.0
Cerebral cortex – VectorsLab https://thenounproject.com/icon/brain-4224212/
Brainstem – Tezar tantular https://thenounproject.com/icon/brainstem-3656737/
Muscle – Amethyst Studio  https://thenounproject.com/icon/muscle-4666756/