Monocular diplopia is a condition which causes double vision in one eye, or seeing two images of an object when only one object is actually present. Common short-term causes of this eye problem are dry eye syndrome, swollen eyelids, and eyelid growths. Typical long-term causes of monocular diplopia are cataracts as well as a corneal aberration known as keratoconus. The most common treatment for monocular diplopia involves attending to these underlying causes.
Dry eye syndrome occurs when there is an insufficient layer of fluid covering the eye, and is sometimes the cause of monocular diplopia. The causes of dry eyes include both under-producing tear glands and a reduced concentration of fatty acid in the tears, which leads to faster moisture evaporation. Lubrication eye drops, prescription or over-the-counter, typically relieve this problem, but in serious cases, the tear duct can be plugged or cauterized to reduce the drainage of the fluid layer from the surface of the eye.
Swollen eyelids, either from an allergic reaction or conjunctivitis, is another cause of monocular diplopia. The swelling applies pressure to the lens and distorts the visual field, sometimes resulting in double vision. If the swelling is due to allergens such as soap, make-up, or contact lenses, eliminating the allergen can clear up the problem.
Infections of, and growths on, the eyelids can also lead to monocular diplopia. Conjunctivitis is a viral or bacterial infection of the eyelid that can cause swelling which can result in double vision. Viral forms of the infection can be treated by cleaning the eye with a wet washcloth several times a day, and bacterial conjunctivitis can be treated with antibiotic eye drops. Ocluar masses on the eyelids are easily removed using conventional surgery, laser surgery, or cyrosurgery.
Cataracts are caused when the normally transparent lens becomes hazy and slightly opaque. The haziness distorts the light passing through the lens, sometimes resulting in monocular diplopia. Most cataracts are caused by aging, as the lens proteins disassociate and the protein parts pool together, creating a blemish in the lens. The treatment for cataracts is to remove the cloudy portion of the lens and replace it with a plastic lens. Local anesthesia is used during the procedure, and it does not require a hospital stay.
The cornea is the transparent coating on the outside of the eye, which works in conjunction with the lens to focus light onto the retina. Keratoconus is a degenerative corneal abnormality, which causes the cornea to become cone-shaped and often causes monocular diplopia. In its early stages, keratoconus can be treated with specialized contact lenses, but as the cornea shape worsens, crescent-shaped inserts can be suspended in the cornea to flatten out the cone shape. Ultimately, a cornea transplant may be necessary. Corneal transplants are typically performed under local anesthesia and last 1-2 hours.