Diplopia, or double vision, is the perception of seeing a single object as two. It arises when the extraocular muscles fail to coordinate, causing visual images to fall on noncorresponding areas of the retinas. Diplopia can be intermittent or constant and may affect near or far vision, depending on the underlying cause. Diplopia can be:

• Monocular (persists when one eye is covered): typically due to optical defects within the eye.

• Binocular (resolves when either eye is covered): due to misalignment of the eyes from neuromuscular or central causes.

Patients may describe images as side-by-side (horizontal diplopia), vertically displaced, or diagonal. Diplopia can be transient or persistent, intermittent or progressive. Associated symptoms such as ptosis, proptosis, headache, or neurologic deficits often guide the underlying diagnosis.

Pathophysiology and mechanisms

Diplopia occurs when light falls on non-corresponding parts of the retina due to failure of ocular alignment. Causes may involve:

• Cranial nerve palsy: CN III (oculomotor), CN IV (trochlear), CN VI (abducens)

• Extraocular muscle pathology: Myopathies (e.g., myasthenia gravis, thyroid eye disease)

• Orbital disorders: Trauma, inflammation, tumors

• Refractive or lens abnormalities (monocular)

• Central causes: Brainstem stroke, MS, tumors

Emergency diagnostic and therapeutic considerations

1. Immediate Evaluation

• Assess for neurologic red flags: altered LOC, new headache, vomiting, seizures, limb weakness.

• Evaluate cranial nerves III, IV, VI for gaze palsies.

• Pupillary exam: A dilated or non-reactive pupil may indicate compressive third nerve palsy (e.g., aneurysm).

• Check for proptosis, ptosis, ophthalmoplegia.

• Vital signs: assess for fever, hypertension, or trauma.

2. Investigations

• Neuroimaging: CT/MRI brain and orbits for suspected aneurysm, tumor, or infarct.

• Blood tests: glucose, thyroid function, acetylcholine receptor antibodies (if myasthenia suspected).

• Lumbar puncture: if encephalitis or meningitis suspected.

• Tensilon (edrophonium) test: for suspected myasthenia gravis.

• Visual acuity, field testing, and extraocular movement assessment.

Medical causes of diplopia

Special populations and situational considerations

Pediatrics

• Most childhood diplopia is due to strabismus or refractive errors.

• If sudden-onset diplopia occurs in school-aged children, rule out brain tumors or trauma.

Geriatrics

• Increased risk for vascular cranial nerve palsies (e.g., diabetes, hypertension).

• Monitor for stroke or TIA if other neurologic symptoms are present.

• Consider polypharmacy and drug side effects (e.g., sedatives, anticholinergics).

Post-surgical/Trauma patients

• Diplopia after eye surgery (e.g., retinal detachment repair) may result from fibrosis.

• Orbital trauma may lead to entrapment of extraocular muscles (e.g., blowout fracture).

Clinical management strategies

immediate interventions

• Address any life-threatening cause urgently (e.g., stroke, aneurysm).

• If neurologic, initiate brain imaging and involve neurology.

• If infectious/inflammatory, start empiric antibiotics or antivirals as needed.

• For myasthenia gravis: consider acetylcholinesterase inhibitors, steroids, or IVIG.

Symptomatic relief

• Temporary occlusion therapy (patch one eye).

• Prism glasses in stable ocular deviation cases.

• Treat underlying causes (e.g., diabetes, thyroid disease).

Patient counseling and prognosis

• Avoid driving or machinery if diplopia persists.

• Teach home safety strategies (e.g., remove hazards, assistive walking).

• Educate on importance of follow-up imaging, neurologic and ophthalmologic evaluation.

• In conditions like myasthenia gravis or MS, offer long-term management and support.

References

1. Ansons AM, Davis H. Diagnosis and management of ocular motility disorders. Wiley Blackwell; 2014.

2. Gerstenblith AT, Rabinowitz MP. The Wills Eye Manual. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2012.

3. Roy FH. Ocular Differential Diagnosis. Clayton, Panama: Jaypee–Highlights Medical Publishers, Inc; 2012.

4. Sheth VS, Marcet MM, Chiranand P, et al. Review Manual for Ophthalmology. Philadelphia: Lippincott Williams & Wilkins; 2012.