diplopia differential diagnosis

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]

Binocular Diplopia

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.