Double vision. also known as Diplopia. is the simultaneous perception of two images of a single object - the patient sees two images of a single thing either all the time, or some of the time. The displacement may be horizontally, vertically or diagonally. Diagonal double displacement (double vision) means both the horizontal lines and vertical lines are being perceived as doubled - also known as oblique separation.
Single binocular vision - each eye of the individual works independently, creating its own, faintly different image. The patient, however, only perceives one image because the brain is able to control the muscles of the eyes so that both of them point accurately at the object the person is looking at. The brain then joins the images produced by both eyes into one image - this is known as single binocular vision .
If, however, the eye muscles are damaged, or even the nerves, or if some health condition has weakened them, the muscles may not be able to control the eyes correctly, resulting in double vision.There are three types of double Diplopia:
- Binocular double vision - both the patient's eyes do not work together properly. The double vision will disappear if the patient covers one eye, or the other.
What are the signs and symptoms of double vision?
A symptom is something the patient feels and reports, while a sign is something other people, including a doctor or nurse may detect. For example, pain may be a symptom while a rash may be a sign.
Double vision. which is sometimes confused with blurred vision. as mentioned above, is when the individual sees two images of a single object. Blurred vision is a single unclear image, while double vision is the perception of two images, when there is only one.
Double vision affects people in different ways. Some patients may experience double vision occasionally, while others have it all the time. Some people say they only experience double vision when they are looking in a specific direction.
If an individual gets double vision when they see in one particular direction, it is most likely due to eye-muscle weakness - either the lateral rectus muscle or the medial rectus muscle. Both muscles are located on either side of the eyeball - their movements make the eyeball move to the left or right.
Patients with muscle paralysis may have a cross-eyed, or wandering eye appearance.
Anybody who develops double vision should see either their GP or an ophthalmologist immediately. Double vision is a sign of several possible medical conditions, some of which may be serious.
Double vision in children
Children are less able to express what is wrong with their eyesight than adults. A child with double vision may narrow their eyes when trying to focus on something (squint). Some kids may cover one eye with their hand, or deliberately close one eye. If a child gazes at things with an unusual head position frequently it could be a sign of double vision.
Childhood double vision can be treated more effectively if diagnosed early on. Therefore, any signs or symptoms of double vision in a child should be reported to a health care professional as soon as possible.
What are the causes of double vision?
- Binocular double vision - most people with double vision have binocular double vision. The patient's eyes are not perfectly aligned - they point at slightly different angles, which results in slightly different images being sent to the brain. However, the images are not similar enough for the brain to create one single, clear image - so, two images are created (double image, double vision).
The most common reason for eyes not being completely aligned is a squint (strabismus). This is due to a weakened or paralyzed eye muscle. Not all squints cause double vision, but most cases of double vision are caused by squints. Squints are common among young children.
The following conditions can cause binocular double vision:
- A thyroid disease. which results in weakened external eye muscles.
- An abnormality in the cornea
- An abnormality in the iris
- An abnormality in the lens of the eye
- An abnormality in the vitreous humor; a gelatinous substance that fills the eye.
- An abnormality in the aqueous humor; a watery fluid that fills the space behind the cornea.
Monocular double vision is commonly caused by:
- Astigmatism - the front surface of the eye (cornea) of a person with astigmatism is not curved properly -
the curve is irregular - usually one half is flatter than the other - sometimes one area is steeper than it should be.
and also (less commonly)..
How is double vision diagnosed?A doctor who specializes in vision and eye conditions and diseases is called an ophthalmologist. If you go to your GP with what appear to be signs and symptoms of double vision, you will most likely be referred to an ophthalmologist.
- Preliminary tests - the specialist will first try to determine whether the patient has monocular or binocular double vision. The patient will be asked to cover one eye and then the other and describe his vision.
What are the treatment options for double vision?Treatment for double vision depends on what type it is: binocular or monocular.
- Binocular double vision treatment - treatment options will depend on several factors, including its cause and prognosis. Treatment may include:
- Eye muscle surgery
- Having a contact lens in one eye which totally blocks vision
- Having an eye patch over one eye
- Receiving a botulinum toxin injection for one of the eye muscles
- Wearing glasses with filters
Children's brains are better able to suppress one of the images, resulting in ignored double vision (the double vision is there, but the brain manages to ignore some of the data so that the patient experiences no symptoms).
If the fault is detected early on during childhood the chances of a total cure are very good. If a squint continues into adult life double vision is much harder to correct.
Botulinum toxin injections may be utilized to treat squints, and some other eye disorders. Small-dose botulinum toxin injections may stop muscle spasms by preventing chemical messages in the nerves. The botulinum toxin is mixed with salt water and injected into the muscle. The patient may feel a bit sore afterwards, but recovery is fast.
The lens may be removed in fragments (Phacoemulsification). The lens may be removed in one piece (extracapsular surgery). An incision is made in the cornea and the IOL is inserted.
An iris claw lens (specially made tinted IOL) may be surgically attacked to the tissue of the iris using a claw-like mechanism. With this procedure the natural lens of the eye is not removed.
Although the IOL procedure has a good success rate, there is a slight risk of the intraocular lens breaking, or damaging the natural lens.
Patients with astigmatism may also benefit from laser surgery.
PreventionThere is nothing people can do to prevent double vision if they have a squint or astigmatism. However, there are steps people can take to prevent or effectively treat underlying causes which increase the risk of double vision.
- Diabetes - patients with diabetes who adhere to treatment protocols have a lower risk of developing double vision, compared to diabetes patients who don't. In other words, if you keep your diabetes under control your risk of double vision is much lower than if you don't.
Diabetes Type II can develop as a result of lifestyle. People who eat a healthy and balanced diet, do plenty of exercise and maintain a healthy bodyweight are much less likely to develop diabetes, and subsequently double vision, compared to people who are obese, do not eat healthily and are physically inactive.
Written by Christian Nordqvist