Diplopia is the official term for double vision. Double vision refers to the phenomenon of seeing multiple images instead of just one. These double images may be side by side or one on top of the other. Double vision can make life a headache–literally. Whether you wear prescription glasses or not, you may experience double vision at some point in your life.
Double vision can be split into two distinct categories: binocular and monocular.
Monocular double vision
Monocular double vision occurs when multiple images are visible in just one eye. So if you close one eye and the double vision goes away, that is monocular double vision.
Monocular double vision is usually a benign side effect of an underlying condition. These underlying causes range from harmless to degenerative. Monocular double vision is usually caused by the following:
- Dry eye
Dry eye, whether temporary or chronic, can result in monocular double vision. Once the eye has been properly lubricated, the double vision should stop.
In severe cases of astigmatism, double vision may present.
Kerataconus is a degenerative disease, and as it progresses, double vision may begin in one eye.
Double vision can be a symptom of cataracts. With cataract treatment, the double vision should cease.
- Retinal problems
Retinal abnormalities like macular degeneration can also cause double vision. A retinal problem is by far the most serious cause of monocular double vision and needs immediate attention.
Binocular double vision
On average, binocular double vision is a far more serious symptom than monocular double vision. Binocular double vision is when multiple images are present in both eyes. Typically, binocular vision is a problem with the brain, blood vessels or nervous system, rather than the result of an eye issue.
The following are some of the most common causes of binocular double vision:
During a stroke, blood may not reach the nerves responsible for the eye muscles, causing double vision.
When blood vessels bulge during an aneurysm, this can place extra pressure on nearby nerves. If the nerve of the eye muscle is affected, this can cause double vision.
- Thyroid problems
The hormone produced in your thyroid gland is called thyroxine. Thyroxine fluctuations can weaken or harm the muscles around the eyes. When eye muscles don’t function properly, double vision can occur.
Diabetes can harm your eyes and vision in a lot of ways. Those with diabetes are at an increased risk of retinal problems like diabetic retinopathy. Diabetes can also harm the nerves responsible for eye control and movement.
- Muscle weakness
Any condition that affects the muscular system has the potential to cause double vision. Myasthenia gravis, a muscular disease, is a common cause of binocular double vision. In rare cases, an unknown disease known only as convergence insufficiency can cause double vision by preventing the eye muscles from lining up correctly.
Tumors in the brain can damage the optic nerve or otherwise impede eye function, causing double vision.
- Multiple sclerosis
Multiple sclerosis and other central nervous system diseases can cause double vision.
Injuries to the head can affect the areas of the brain that control the eyes. Concussions, for example, frequently result in double vision. Physical injuries to the eye itself, such as swelling from a black eye, can also make you see double.
Handling double vision
Double vision can be tricky to treat because there are so many possible causes. If you experience double vision, the first thing to do is to check if it is binocular or monocular in nature. To do this, alternatively close one eye at a time. If the double vision remains, then it is binocular. If the double vision comes and goes when you close each eye, then it is monocular.
The next step is to call your eye doctor. Your optometrist will want to know if you are experiencing double vision in one or both eyes so be sure you’ve already determined that. They will then decide if you need to come in immediately or if you can wait and schedule an appointment.
Double vision should never be ignored if you are unsure of the cause. It is always safer to make a quick call to the eye doctor than to risk permanent damage.
Double vision and prescription glasses
In some cases, a new pair of prescription eyeglasses can cause temporary double vision. This is usually not cause for alarm. Mention to your eye doctor that your new glasses are making you see double so they can double check your prescription. However, double vision from new glasses usually subsides quickly on its own.
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