Neuro-ophthalmology
What causes double vision?
Double vision means seeing two images of one object. If it disappears when one eye is covered, the two eyes are not aligned, often because a nerve or muscle controlling movement is affected. If it persists with one eye covered, the cause is within that eye, such as cataract or a dry, irregular surface. Sudden double vision needs prompt assessment.
The first question to answer
Cover one eye, then the other. Double vision that goes away when either eye is covered comes from misalignment of the two eyes. Double vision that remains in one eye when the other is covered comes from that eye itself, and is usually a blurring or ghosting rather than two separate images.
Causes of misalignment
- Nerve palsies affecting the muscles that move the eye, which can follow diabetes or high blood pressure, or result from pressure inside the head
- Thyroid eye disease, which restricts muscle movement
- Myasthenia gravis, where the double vision and drooping lid vary through the day and worsen with tiredness
- Injury to the bones or muscles around the eye
- A long standing squint that has decompensated
Causes within one eye
- Cataract, which can split light into ghost images
- Significant astigmatism or an incorrect glasses prescription
- A dry or irregular corneal surface, including keratoconus and scarring
- Displacement of the lens or a lens implant
Assessment and treatment
Eye movements, alignment, lids and pupils are examined, and the cause guides treatment. Some nerve palsies recover over weeks to months, particularly those related to diabetes or blood pressure. Prisms in glasses, occlusion, treatment of the underlying condition and, in selected cases, squint surgery are all used. Treating high blood pressure, diabetes and thyroid disease is part of care.
When to seek urgent assessment
- Sudden double vision, especially with headache, a drooping lid or an enlarged pupil, which needs emergency assessment
- Double vision with weakness, numbness, slurred speech or difficulty walking, which may indicate a stroke and needs emergency care
- Double vision after a head injury
- Double vision with pain on eye movement or a bulging eye
Frequently asked questions
- Will double vision go away on its own?
- Some causes, such as certain nerve palsies linked to diabetes or blood pressure, improve over several months. Others do not, so the cause needs to be established rather than waiting.
- Can glasses fix it?
- Prisms built into glasses help selected cases of small, stable misalignment. They are not a solution for every cause.
Concerned about these symptoms?
Arrange an eye examination with our consultant ophthalmologist in Garki, Abuja.
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