What Is Diplopia?
Diplopia is when you see two images of the same thing. You might know it as double vision.
You might have diplopia in one eye or both. Generally, double vision in both eyes is more serious than if you have it in just one.
Diplopia Types and Causes
Double vision in only one eye is called monocular diplopia. It might involve your:
Cornea. This is the clear window into your eye. Its main job is to focus light. If your double vision goes away when you cover one eye but remains when you switch and cover the other eye, you might have cornea damage in the eye that’s seeing double.
It could be that your cornea in that eye is uneven. Glasses can probably fix the problem. Damage can be from:
Lens. This sits behind your pupil, the opening in your eye, and helps focus light onto your retina in the back of your eye.
Cataracts are the most common lens problem. Surgery almost always fixes them. Cataracts can be worse in one eye than the other and can grow at different rates between your 2 eyes.
Double vision when both eyes are open is called binocular diplopia. It might involve your:
Muscles. They control eye movement and keep your eyes aligned with each other. If a muscle in one eye is weak, it won't move in sync with the other eye. When you look in a direction controlled by the weak muscle, you see double. Eye muscle problems can be from:
- A problem with the nerves that control them
- Myasthenia gravis, an autoimmune illness that stops nerves from telling your muscles what to do. Early signs include double vision and drooping eyelids.
- Graves' disease, a thyroid condition that affects eye muscles. It can cause vertical diplopia, where one image is on top of the other.
Nerves. They carry information from your brain to your eyes. Problems with them can lead to double vision:
- Multiple sclerosis can affect nerves anywhere in your brain or spinal cord. If it damages the nerves that control your eyes, you may see double.
- Guillain-Barre syndrome is a nerve condition that causes growing weakness. Sometimes, the first symptoms are in your eyes, including double vision.
- Diabetes can cause nerve damage in the muscles that move your eyes. That can lead to double vision.
Brain. The nerves that control your eyes connect directly to your brain, where images are handled. Many causes of double vision start in the brain. They include:
If you have double vision, you may also notice:
Double vision that's new or doesn’t have a clear cause can be serious.
Tell your doctor about all your symptoms. Before your appointment, think about these questions:
- When did the double vision start?
- Have you hit your head, fallen, or passed out?
- Were you in a car accident?
- Is the double vision worse at the end of the day or when you're tired?
- Have you had any other symptoms besides double vision?
- Do you tend to tilt your head to one side? You might not know that you do it. Look at old pictures or ask family members.
- Does the double vision happen only with both eyes open?
Try focusing on something that isn’t moving, like a window or a tree. Ask yourself these questions:
- Are the two images side by side, or is one on top of the other? Are they slightly slanted? Which one is higher or lower?
- Are both images clear but not in line? Or, is one blurry and the other clear?
- Cover one eye and then switch. Does the problem go away when either eye is covered?
- Imagine that your field of vision is a clock face. Move your eyes around the clock from noon to 6 and around to 12 again. Is your vision better or worse at any position?
- Tilt your head to the right and then to the left. Do any of these positions improve your eyesight or make it worse?
The most important thing is to identify and treat the cause.
There’s no way to prevent diplopia from cataracts or some other causes. But, to avoid injuries that can give you double vision, wear your seat belt when you’re in a car and use protective goggles or headgear when you play sports or do activities that might hurt your eyes. If you have diabetes, keep your blood sugar under control to lower your chance of nerve damage.
Almost 70% of cases get better with medication and surgery, such as cataract surgery. Sometimes, diplopia clears up on its own. Your results will depend on the cause of your double vision.
If your double vision is permanent, treatments can help you live with it. Special eyewear, like an eye patch or prism glasses, can ease the effects.