Double vision, or diplopia, is one of the most common symptoms that are presented to an optometrist’s office. Not all double vision symptoms are the same though; “double vision” can mean many different things and can come in a variety of forms. Binocular double vision means both eyes have to be opened for diplopia to be present. In true binocular diplopia cases, covering one eye would resolve the doubling effect. Monocular diplopia would occur through one eye only and covering one of the two eyes would not resolve the diplopia.
Binocular diplopia can present in a horizontal or vertical fashion and can be caused by a variety of reasons. Muscle misaligned is often a leading cause for diplopia. Depending on which ocular muscle is affected will dictate the resulting doubling in vision; diagnostic tests are performed to infer and identify the affected muscle and thus help with diagnosing the condition that may be involved.
Unlike binocular double vision, monocular diplopia is usually due to media opacity or refractive error. “Shadowing” or “overlapping effect” are some of the common ways patients describe this monocular diplopia. Other common causes for such symptoms include, cataracts, regular astigmatism, or Keratoconus (corneal disease causing irregular astigmatism).
Once the type and nature of diplopia is identified by your optometrist a treatment plan and a course of action is outlined. Certain binocular double vision presentations are serious and the underlying cause should be addressed urgently. Acute presentations of vertical diplopia, for example, can be caused by serious conditions and should be investigated immediately. Monocular cases of diplopia are often resolved by addressing the causing factor. For example, when cataract is the offending factor, removing it would usually resolve the symptoms, other times the symptoms are due to uncorrected refractive error. Correcting the refractive error with spectacles, contract lens therapy, or laser refractive surgery, can oftentimes remedy those conditions. However, it is imperative that an accurate diagnosis for the cause of diplopia is made before treatment options are discussed.
Many forms of binocular diplopia are corrected with prism therapy and/or vision therapy. Prism therapy in spectacles can vary in nature and could include Base Out and Base In prism for vertical deviations or Base Up and Base Down for vertical diplopic presentations. Vision therapy is also indicated in certain cases when certain intraocular muscles are weakened and need strengthening for better alignment; the eye muscles ability to converge or diverge is improved through vision therapy. Depending on the severity and type of each case, some conditions can be treated with in-home vision therapy programs such as HTS (Home Therapy System). Other patients might require office based vision therapy and more sessions with a vision therapist in the office for better outcome.