Double Vision (Diplopia)

What Is It?

Double vision, also called diplopia, causes a person to see two images of a single object. There are two types of double vision: monocular and binocular.

Monocular diplopia is double vision in only one eye. The double vision continues even when the other eye is covered. The doubling does not go away when you look in different directions. Monocular diplopia can be caused by:

  • Astigmatism — This is an abnormal curvature of the front surface of the cornea.

  • Keratoconus — The cornea gradually becomes thin and cone-shaped.

  • Pterygium — This is a thickening of the conjunctiva, the thin mucous membrane that lines the inner surface of the eyelids and the whites of the eyes. The thickening extends on the cornea, the clear part of the surface of the eye.

  • Cataracts — The lens gradually becomes less transparent. Risk factors include being older than 65, having eye trauma or long-term diabetes, smoking, using steroid medications or having radiation treatments.

  • A dislocated lens — The ligaments that hold the lens in place are broken, and the lens moves out of place or wiggles. This can be caused by trauma to the eye or a condition known as Marfan's syndrome.

  • A mass or swelling in the eyelid — This condition can press on the front of the eye.

  • Dry eye — Your eyes do not produce enough tears.

  • Some retinal problems — Double vision can happen when the surface of the retina is not perfectly smooth, which can have a variety of causes.

Binocular diplopia is double vision related to a misalignment of the eyes. The double vision stops if either eye is covered. Any problem that affects one or more of the muscles around the eyeball that control the direction of the gaze can cause binocular diplopia. These are called extraocular muscles. Such problems include:

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