Double vision is the perception of seeing two images of a single object. This symptom can manifest as the images appearing side-by-side, one above the other, or diagonally offset. Diplopia requires immediate professional evaluation by an eye care specialist or other healthcare provider. Double vision can stem from a variety of sources, ranging from simple refractive errors to complex systemic or neurological conditions. Determining the specific origin is the first step toward finding an effective solution.
Classifying the Underlying Causes
A proper treatment plan for double vision depends on identifying the underlying cause, categorized as monocular or binocular diplopia. Monocular diplopia is present when the double image persists even after the unaffected eye is covered, meaning the issue lies within the structure of the seeing eye. This type is associated with problems that interfere with how light is focused onto the retina.
Common causes of monocular diplopia include irregularities on the eye’s surface, such as astigmatism or corneal scarring. A frequent culprit is a cataract, which is a clouding of the eye’s natural lens that distorts the path of incoming light. Conditions like dry eye syndrome or keratoconus, where the cornea thins and bulges into a cone shape, can also lead to monocular double vision.
Binocular diplopia occurs when the double vision disappears if either eye is covered, indicating the two eyes are not working together in alignment. This type points to a problem with the muscles that control eye movement, the nerves that supply those muscles, or the parts of the brain that coordinate the eyes. The misalignment causes the brain to receive two slightly different images, which it cannot fuse into a single picture.
Causes of binocular diplopia include conditions like strabismus, cranial nerve palsies due to stroke or injury, or systemic diseases. Autoimmune disorders, such as myasthenia gravis, can weaken the eye muscles. Thyroid disease, specifically Graves’ ophthalmopathy, can restrict muscle movement. Binocular double vision can signal a neurological issue, such as an aneurysm or tumor, requiring urgent medical attention.
Immediate Symptom Management
While waiting for a definitive diagnosis or permanent treatment, several temporary measures can manage double vision. The most straightforward approach is occlusion therapy, which involves physically blocking the vision in one eye, eliminating the double image. This is often achieved by wearing a simple eye patch, though it sacrifices binocular vision and depth perception.
A less conspicuous option involves applying an occlusive contact lens or opaque tape to the inside of a glasses lens, blurring the image enough to prevent the double perception. For binocular diplopia, press-on prism lenses, known as Fresnel prisms, offer a short-term, adjustable solution. These thin, flexible plastic sheets stick onto a glasses lens to temporarily bend the light and shift the image, helping the eyes fuse the images.
Fresnel prisms are useful during the diagnostic phase because their strength can be easily changed as the eye alignment fluctuates or as the underlying condition resolves. These temporary aids should only be used under the guidance of an eye care professional. They provide functional relief, allowing the individual to perform daily tasks until a long-term fix is implemented.
Definitive Medical Solutions
Definitive solutions for double vision are tailored to whether the underlying cause is monocular or binocular. For monocular diplopia, treatment focuses on correcting the structural or refractive issue within the affected eye. If a cataract is the cause, surgical removal of the cloudy lens and replacement with an artificial intraocular lens typically resolves the double vision.
If monocular diplopia is caused by astigmatism, specialized corrective eyewear or contact lenses, including custom scleral lenses for keratoconus, can correct the light focus. Corneal irregularities or scarring may require refractive surgery or, in severe cases, a corneal transplant to restore a smooth optical surface. Treating underlying issues like dry eyes with lubricating drops or medicated treatments is also necessary.
For binocular diplopia, treatment involves addressing the systemic cause and the eye misalignment. If the double vision is caused by a condition like thyroid eye disease or myasthenia gravis, medical management with medications is the primary treatment. Once the underlying condition is stable, eye alignment issues can be addressed through three main corrective avenues.
The first avenue is the incorporation of permanent, ground-in prism lenses into eyeglasses, which redirect light to ensure the images fall on corresponding parts of the retina. Unlike temporary Fresnel prisms, these are polished directly into the lens and are used when the eye misalignment is stable. The second option is vision therapy, involving specialized eye exercises to strengthen eye muscles and improve coordination, often used for convergence insufficiency. Finally, if conservative measures fail or the misalignment is significant, eye muscle surgery can physically adjust the length or position of the extraocular muscles to permanently realign the eyes.