Double vision, or diplopia, is a symptom to take seriously. Many causes of double vision are fairly innocuous-or you may have had a gin and tonic too many-but some can be quite serious and need immediate attention.
How Normal Vision Works
The seemingly automatic process of seeing one clear image when we open our eyes is dependent on many areas of our vision system all working properly and at the same time.
- The cornea is the clear window into the eye. It does most of the focusing of incoming light, and is ideally as spherical as possible for the sharpest image.
- The lens is behind the pupil. It also helps focus light onto the retina.
- Muscles of the eye — extraocular muscles — rotate the eye.
- Nerves carry visual information from the eyes to the brain.
- The brain is where several areas process visual information from the eyes.
If you are experiencing double vision, it may be as a result of a problem with any of those functioning parts of the vision system. Double vision needs to be reported promptly.
Problems with the cornea often cause double vision in only one of your eyes, and if you cover it with your hand the double vision goes away. The problem is that an abnormal corneal surface distorts the incoming light badly and causes double vision. Damage can happen in several ways:
- Infections of the cornea, such as herpes zoster, or shingles, can distort the cornea.
- Corneal scars can alter the cornea, creating unequal visual images.
- Dryness of the cornea can create double vision.
- Lens problems. Cataracts are the most common problem with the lens that causes double vision. If cataracts are present in both eyes, images from both eyes will be distorted. Cataracts are often correctable with minor surgery.
If a muscle in one eye is weak-much weaker than the other eye, then it can’t move smoothly in conjunction with its mate. This will cause you to experience double visions. Eye muscle problems stem from the following:
- Myasthenia gravis is an autoimmune illness that blocks the stimulation of muscles by nerves inside the head. The earliest signs are often double vision and drooping eyelids, or ptosis.
- Graves’ disease is a thyroid condition that affects the muscles of the eyes. Graves’ disease commonly causes vertical diplopia. With vertical diplopia, one image is on top of the other.
- Nerve problems. Several different conditions can damage the nerves that control eye muscles and lead to double vision
- Multiple sclerosis can affect nerves anywhere in the brain or spinal cord. If the nerves controlling the eyes are damaged, double vision can result.
- Guillain-Barre syndrome is a nerve condition that causes progressive weakness. Sometimes, the first symptoms occur in the eyes and cause double vision.
- Uncontrolled diabetes can lead to nerve damage in one of the eyes, causing eye weakness and double vision.
The nerves controlling the eyes connect directly to the brain, and visual processing occurs there as the brain makes sense of the image generated. Any of the following issues-and these are all SERIOUS issues-will cause double vision. They include:
- Increased pressure inside the brain from trauma, bleeding, or infection
- Brain tumours
- Migraine headaches
What Are the Symptoms of Double Vision?
Double vision can occur by itself with no other symptoms. Depending on the cause, other symptoms may be present with double vision, such as:
- Misalignment of one or both eyes (a “wandering eye” or “cross-eyed” appearance)
- Pain with eye movements in one or both eyes
- Pain around the eyes, such as in the temples or eyebrows
- Weakness in the eyes or anywhere else
- Droopy eyelids
What Should I do?
Double vision that’s new or unexplained needs medical attention right away. With so many potentially serious causes for double vision, it’s important to discover the reason without delay.
Once you have established the cause of your double vision, see if you might be a candidate for Laser Eye Surgery which can help in cases of astigmatism or other refractive errors by reshaping the cornea using laser.
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