https://eyewiki.org/Basic_Approach_to_Diplopia
Diplopia (double vision) is broadly split into monocular and binocular causes, distinguished by whether the double vision persists when covering one eye. [1, 2]
Monocular Diplopia
Persists when the unaffected eye is covered; typically originates within the eye itself rather than the nervous system. [
1,
2]
- Refractive & Ocular Surface: Uncorrected astigmatism, dry eye syndrome, tear-film abnormalities
- Lens & Media: Cataracts, lens subluxation or dislocation
- Corneal & Retinal: Corneal scars/irregularities (e.g., keratoconus), macular disease
- Central (Rare): Cerebral polyopia (bilateral, persists in either single eye view, caused by occipital/visual cortex lesions) [1, 2, 3, 4, 5, 6, 7]
Resolves immediately when either eye is closed; indicates eye misalignment caused by neuromuscular, mechanical, or central/peripheral nervous system disorders. [
1,
2]
- Cranial Nerve (CN) Palsies:
- CN III (Oculomotor): Causes ptosis, a "down and out" eye, and a dilated pupil; driven by microvascular ischemia (diabetes/hypertension), posterior communicating artery (PCoA) aneurysms, or midbrain stroke.
- CN IV (Trochlear): Causes vertical/torsional diplopia worse on downgaze and contralateral head tilt; caused by trauma, microvascular disease, or congenital decompensation.
- CN VI (Abducens): Causes horizontal gaze failure/abduction deficit; caused by microvascular ischemia, elevated intracranial pressure, or pontine lesions. [1, 2, 3, 4]
- Neuromuscular Junction:
- Myasthenia Gravis: Fluctuating, fatigable extraocular weakness and ptosis with pupil-sparing ophthalmoplegia. [1, 2]
- Extraocular Muscle & Orbital Disorders:
- Thyroid Eye Disease (Graves'): Restrictive myopathy causing painful or painless restriction, lid retraction, and proptosis.
- Orbital Pathologies: Orbital floor blowout fractures (muscle entrapment), orbital pseudotumor, inflammation, or neoplasm. [1, 2, 3]
- Central / Supranuclear Pathways:
- Internuclear Ophthalmoplegia (INO): Lesion of the medial longitudinal fasciculus (MLF) causing impaired adduction on gaze; frequently seen in Multiple Sclerosis or brainstem stroke.
- Other Central Causes: Skew deviation, brainstem gliomas, Wernicke encephalopathy, or demyelinating disease. [1, 2, 3]
If you are evaluating a specific patient, tell me:
- Is the double vision monocular or binocular?
- Is it horizontal, vertical, or torsional?
- Are there associated red flags (pain, ptosis, pupillary changes, or other neurological deficits)?
I can help narrow down the precise localization and differential.