Diplopia can be the first sign of serious neurological or systemic disease, but it may also arise from benign refractive errors. A careful history and examination is essential to distinguish life-threatening causes (e.g. aneurysm, stroke) from correctable ones (e.g. refractive error, strabismus).

🩺 History & Examination Tips

History: Onset (sudden vs gradual), monocular vs binocular diplopia, variability (fatigue → myasthenia), associated symptoms (headache, ptosis, thyroid signs).
Examination: Check ocular alignment, extraocular movements, ptosis, pupillary reactions, presence of proptosis or lid lag, and neurological signs.
Key discriminator: Monocular diplopia → usually refractive/ocular; Binocular diplopia → usually neuromuscular or neurological.

🧠 Causes of Diplopia

Cause	Clinical Presentation	Diagnostic Tests	Management
📏 Refractive Errors (Astigmatism, Uncorrected Vision)	Blurred or double vision Worsens with fatigue Improves with glasses/contact lenses	Visual acuity test Refraction test Comprehensive eye exam	Corrective lenses Regular check-ups Refractive surgery in some
👓 Strabismus (Esotropia, Exotropia)	Eye misalignment Intermittent or constant diplopia Head tilt or squinting	Cover-uncover test Corneal light reflex Prism test	Patching for amblyopia Prism or corrective glasses Strabismus surgery
🧵 Cranial Nerve Palsies (III, IV, VI)	III: Ptosis, "down & out" eye, dilated pupil (compressive causes) IV: Vertical diplopia, worse on stairs, head tilt VI: Horizontal diplopia, failure to abduct	MRI/CT (exclude aneurysm, tumour, stroke) Pupil exam for III palsy Blood tests for diabetes/HTN	Observation for microvascular causes Surgery if compressive Prism glasses / botox for residual diplopia
⚡ Myasthenia Gravis	Fluctuating diplopia Fatigue-related ptosis Generalised muscle weakness	AChR antibody test Tensilon test (historical) EMG studies	Anticholinesterase drugs Immunosuppressants IVIG/plasmapheresis if severe Thymectomy in selected patients
🦋 Thyroid Eye Disease	Diplopia from EOM inflammation Proptosis, lid lag Hyperthyroid symptoms	Thyroid function tests Orbital CT/MRI Thyroid antibodies	Steroids for inflammation Orbital decompression if severe Radioiodine / anti-thyroid therapy Prism glasses or surgery
🧩 Stroke / Brain Lesions	Sudden diplopia with neuro deficits Vertical or horizontal depending on site Internuclear ophthalmoplegia possible	MRI/CT brain Carotid Doppler Bloods for vascular risk factors	Acute stroke management (thrombolysis/thrombectomy) Neurorehabilitation Prism glasses or patching Tumour surgery/radiotherapy

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Diplopia (Double Vision)

🩺 History & Examination Tips

🧠 Causes of Diplopia

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