Double vision can be a sign of a stroke, particularly one affecting the back of the brain. It is one of the five key warning signs of posterior circulation stroke, which accounts for about 20% of all strokes caused by a blood clot. If double vision comes on suddenly and is paired with dizziness, slurred speech, difficulty swallowing, or drowsiness, treat it as a medical emergency.
Why Stroke Causes Double Vision
Your eyes move in sync because of precise coordination between several nerves and brain regions. A stroke that damages the brainstem or cerebellum, the areas at the base and back of the brain, can disrupt that coordination. When the two eyes no longer aim at the same point, you see two overlapping images.
The specific pattern of double vision depends on where the stroke occurs. A clot in the pons (a section of the brainstem) can prevent one eye from turning inward properly, producing side-by-side double images. Damage to the cerebellum can add a vertical component, making one image appear higher than the other. In a published case report, a woman with a brainstem stroke woke up with painless horizontal double vision caused by exactly this kind of eye-movement disconnect, with brain imaging revealing small lesions in the pons and cerebellum.
How to Tell If It’s a Stroke
Double vision from a stroke almost always appears in both eyes. If you cover one eye and the doubling goes away, that’s binocular diplopia, meaning the problem is in how your eyes coordinate rather than in the eye itself. Monocular diplopia, where the doubling persists even with one eye closed, is nearly always caused by a focusing problem within the eye and is not typically a stroke sign.
The updated stroke awareness acronym BE-FAST includes vision changes under the “E” for Eyes. Sudden blurred vision, double vision, or loss of vision in one or both eyes all qualify. The remaining letters cover Balance problems, Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services. Posterior circulation strokes are easy to miss because the most familiar screening tools focus on face, arm, and speech. Standard stroke scales don’t even include dizziness or vertigo, which means these strokes can be overlooked in early assessments.
Emergency physicians sometimes use a bedside exam called the HINTS test to distinguish a stroke from a benign inner-ear problem. It checks three things: how the eyes respond when the head is turned quickly, whether involuntary eye movements change direction when the patient looks in different directions, and whether one eye sits higher than the other. A specific combination of results on this test points strongly toward a stroke rather than a simple vestibular issue.
Other Symptoms That Appear Alongside It
Posterior circulation strokes are associated with five overlapping symptoms sometimes called the “five D’s”: dizziness, drowsiness, dysarthria (slurred or garbled speech), diplopia (double vision), and dysphagia (trouble swallowing). Two or more of these appearing together raises serious suspicion for a stroke in the back of the brain. You don’t need all five to be present.
About 60% of stroke patients experience some form of visual impairment in the acute phase. Among stroke patients whose eye movements are affected by nerve damage, roughly 61% report double vision as their primary visual symptom, making it the most common complaint in that group. Blurred vision and visual field loss are also reported but less frequently.
Other Causes of Sudden Double Vision
Not every case of sudden double vision is a stroke, but several of the alternatives are also serious. A brain aneurysm pressing on a nerve can cause double vision along with a drooping eyelid and a pupil that won’t constrict. A fixed, dilated pupil combined with headache and double vision is considered a neurosurgical emergency requiring immediate imaging.
Giant cell arteritis, an inflammatory condition of blood vessels that primarily affects people over 50, can also cause double vision. Other clues include a new headache concentrated at the temples, jaw pain while chewing, unexplained weight loss, and night sweats. This condition needs urgent treatment because it can lead to permanent vision loss.
Less urgent causes include thyroid eye disease, which can push the eyes forward and restrict movement, and myasthenia gravis, an autoimmune condition where double vision worsens with fatigue and improves after rest. These conditions develop more gradually and carry different accompanying symptoms, but any new, unexplained double vision warrants prompt evaluation.
Recovery and Treatment After Stroke
Double vision caused by a stroke often improves on its own as the brain heals, but the timeline varies widely. Some people notice improvement within weeks, while others still have symptoms months later. Studies that recruited patients between three and six months after a stroke found it difficult to separate the effects of treatment from natural recovery, which suggests the brain is still actively repairing eye-movement pathways during that window.
Prism lenses are the most commonly used treatment for persistent post-stroke double vision. These are special lenses, sometimes applied as thin stick-on sheets to regular glasses, that bend light so the two images merge into one. In a study of prism wearers, 74% reported a positive difference after six weeks, and of those, 93% continued wearing the prisms for up to three months. Orthoptists (specialists in eye alignment) prescribe prisms in about 93% of cases involving eye-movement problems after stroke, often combined with advice on head positioning and convergence exercises.
If double vision doesn’t resolve with time or prisms, covering one lens of your glasses with an opaque patch eliminates the second image and makes daily tasks like reading and walking safer. Rehabilitation typically begins within the first two to six weeks after the stroke, with most treatment programs continuing for up to three months.