Diplopia (Double Vision)

What is Diplopia (Double Vision)?

Diplopia — commonly called double vision — occurs when the two eyes fail to work together to produce a single, fused image. The brain receives two slightly misaligned images and cannot suppress one of them. It may be monocular (affecting one eye only, persisting when the other eye is closed) or binocular (affecting both eyes together, resolving when one eye is covered). Binocular diplopia is almost always caused by a misalignment of the eyes — a squint (strabismus) — and is the type most commonly assessed and treated by Mr Mohyudin.

Symptoms

• Two images of the same object, side by side, diagonally placed, or one above the other
• Symptoms that resolve when one eye is closed (binocular diplopia)
• Head tilting or turning to find a position that reduces double vision
• Difficulty reading, driving, or judging distances
• Associated eyelid drooping (ptosis), which may suggest a neurological cause
• Eye pain or headache in some cases

Causes

• Strabismus (squint) — the most common cause of binocular diplopia; may be childhood-onset or acquired in adulthood
• Thyroid eye disease (Graves' orbitopathy) — inflammation and fibrosis of the extraocular muscles
• Third, fourth, or sixth cranial nerve palsy — may result from diabetes, hypertension, aneurysm, or tumour
• Myasthenia gravis — neuromuscular junction disorder causing variable, fatigable diplopia
• Orbital trauma — blow-out fracture entrapping an extraocular muscle
• Cataract or corneal irregularity — typically causes monocular diplopia
• Decompensated phoria — a previously well-controlled latent squint breaking down under stress or illness

Diagnosis

Assessment includes cover/uncover and alternate cover tests to measure the angle of deviation, Hess chart and Lees screen to identify which muscle is restricted, prism bar measurement, and dilated fundus examination. Neuroimaging (MRI brain and orbits) is arranged urgently when a vascular or compressive cause is suspected. Blood tests including thyroid function and acetylcholine receptor antibodies where appropriate.

Treatment

Management depends on the underlying cause. Fresnel prisms applied to spectacles can provide temporary relief while the cause is investigated or while waiting for surgery. Botulinum toxin injection to an overacting muscle may help in selected cases. Squint surgery to realign the eyes is the definitive treatment for stable, longstanding diplopia due to strabismus. Mr Mohyudin specialises in strabismus surgery in both adults and children, including complex cases with restricted ocular motility.