Double visible (or diplopia) is a condition in which one sees two images where there is one. Here, the images can seem to be on top of each other or side by side. Sudden double vision can develop due to multiple reasons, including an injury or underlying health issues. The condition affects reading ability, movement, and balance. Nevertheless, recognizing the causes and early signs can help one get appropriate treatment to restore regular vision.

Symptoms
Some common symptoms of double vision are:

– Headache
– Wandering or crossed eyes
– Nausea
– Droopy eyelids
– Painful eye movement
– Eye weakness

When children experience double vision, they may flick their eyes side to side, position their heads in an unusual way while looking at something, cover one eye with their hands, and squint to boost vision.

Causes
Some people experience binocular double vision, i.e., they see dual images only when both eyes are open. So, as soon as they close one eye, the issue subsides. On the other hand, monocular diplopia stems from an issue with a single eye. Here is a look at the causes associated with each type of double vision:

Monocular double vision: This type is associated with corneal or lens damage. Cornea is the clear window inside the eye that focuses light. Monocular diplopia can stem from an uneven cornea; wearing glasses is a common treatment option here. Corneal damage may be brought on by dryness, scars, herpes or shingles infection, or keratoconus. Alternatively, issues with the eye lens (the part that focuses the light on the retina and the back of the eye) could be a cause. For instance, one of the most common lens-related issues, cataracts, can trigger double vision. Surgery can correct this issue.

Binocular double vision: Here, damage to the nerves or eye muscles can cause double vision. The nerves transfer information from the brain to the eyes, while muscles control eye movements. Here are a few causes of nerve and muscle damage:

– Guillain-Barre syndrome is a condition that leads to weakness and triggers diplopia.
– Multiple sclerosis affects the spinal cord and the nervous system, potentially damaging the nerves controlling the eyes.
– Diabetes can cause nerve damage.
– Graves’ disease, a thyroid condition, can weaken eye muscles.
– Myasthenia Gravis, an autoimmune condition, can affect the neuromuscular function related to eye movement.

Additionally, the brain plays a key role in processing images. So, issues like migraine, tumors, increased pressure in the region (due to infection, injury, or bleeding), aneurysms, and strokes can increase the risk of double vision.

Diagnosis
If one notices any signs of diplopia, they should consult an ophthalmologist for a complete eye examination. People with monocular double vision may not need further tests beyond the eye exam. However, those with binocular vision might require the imaging tests like a CT scan or MRI along with blood tests for a diagnosis. The imaging tests present a comprehensive picture of the eye and surrounding area to identify issues concerning the spine, brain, and bones.

Treatment options
Treating the underlying cause can correct sudden double vision. Additionally, doctors may recommend the following options:

Special lenses: Lenses equipped with prisms can realign the images from both eyes.

Vision therapy: This comprises exercises to retrain the eyes.

Eye muscle surgery: This is an option for those with weak eye muscles.