Diplopia (Double Vision): Types, Causes, Evaluation & Treatment
Diplopia — perception of two images of a single object — results from misalignment of visual axes. It is a symptom, not a disease, and always warrants investigation.
Classification
| Type | Definition | Key Feature | Common Causes |
|---|
| Monocular | Persists with one eye covered | Optical/media problem in that eye | Cataract, corneal irregularity (keratoconus, scar), lens dislocation, retinal edema/detachment, uncorrected astigmatism, dry eye |
| Binocular | Resolves when either eye covered | Ocular misalignment (strabismus) | CN III/IV/VI palsy, thyroid eye disease, myasthenia gravis, orbital fracture, brainstem stroke, tumor, decompensated phoria |
Critical Distinction
Monocular diplopia = eye problem (cornea, lens, retina). Binocular diplopia = neurologic/neuromuscular/orbital problem. This distinction directs the workup.
Clinical Evaluation
- History: Onset (sudden/gradual), constant/intermittent, direction of separation (horizontal/vertical/torsional), associated symptoms (ptosis, pain, pupil, weakness, trauma).
- Monocular test: Cover each eye.
- Ocular motility: Versions, ductions, Hess screen.
- Pupils: Size, reactivity, RAPD.
- Orbital exam: Proptosis, resistance to retropulsion.
- Neurologic exam: CNs, motor, sensory, reflexes.
Targeted Workup
- Monocular: Slit-lamp, refraction, corneal topography, OCT, B-scan.
- Binocular + acute/painful/pupil-involving CN III palsy: Emergent CTA/MRA (rule out aneurysm).
- Binocular + vascular risk factors (DM, HTN), pupil-sparing: MRI brain/orbits, vascular workup.
- Thyroid eye disease: TSI, thyroid panel, orbital MRI/CT.
- Myasthenia: AChR/ MuSK antibodies, ice pack test, edrophonium, SFEMG.
- Orbital trauma: CT orbits (bone windows).
Treatment
- Monocular: Treat underlying (cataract surgery, corneal transplant, retinal repair, refractive correction).
- Binocular:
- Prisms (Fresnel press-on → ground-in) for small, stable deviations.
- Vision therapy (convergence insufficiency).
- Botulinum toxin (acute CN palsy, thyroid eye disease).
- Strabismus surgery (stable deviation >6–12 months).
- Treat underlying: immunosuppression (myasthenia, TED), anticoagulation (ischemic CN palsy), tumor resection.
Urgent Referral
Sudden binocular diplopia + headache/pupil abnormality/neurologic deficit → ER for stroke/aneurysm/tumor exclusion.
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