What is Diplopia?
Also known as double vision, diplopia is an eye condition in which a person sees a double image of a single object. When double vision affects a single eye, it is called monocular diplopia, and in binocular diplopia, both eyes of a person get affected.
Let’s understand all about diplopia, it’s types, causes, diagnostic tests, and treatment of options.
Types of diplopia
On the basis of separation of double images, diplopia can be classified as horizontal and vertical double vision. Similarly, diplopia can be classified as monocular and binocular based on the affected eye, whether a single eye or both eyes being affected.
Here, the two images are seen on top of one another in a vertical plane.
Here, the two images are placed side by side in a horizontal plane.
Monocular diplopia (double vision)
Although it is less common, it exists in one eye when the other eye is closed.
It is the condition in which the double vision ceases when you close your one eye, but persists while opening both eyes.
Causes of double vision
Diplopia can happen for many reasons, from dry eyes to severe ocular diseases. Temporary, transient diplopia can be seen in tired condition. Likewise, drinking too much alcohol causes double vision that comes and goes i.e. intermittent diplopia. Other causes of double vision are mentioned below.
Causes of monocular diplopia
Astigmatism double vision occurs due to irregular or uneven curvature of the cornea. It is the major cause of monocular double vision, but it also results in binocular diplopia. It can be easily cured using prescription eyeglasses, contact lenses, or doing refractive surgery.
Dry eye is what causes double vision that comes and goes i.e. transient diplopia.
The gradual thinning and steepening of the cornea, either anteriorly or posteriorly causes a double image in affected eyes.
It is a wing-shaped fold of conjunctiva encroaching upon the cornea from either side. The continuous stretching of cornea gives rise to astigmatism and hence causes astigmatism double vision.
It gives rise to astigmatism due to continuous pressing oh the cornea of the affected eye.
A cataract is a gradual loss of transparency of natural crystalline lens which occurs due to age, trauma, smoking, steroid use, diabetes, or radiation exposure.
A dislocated or subluxated lens
If the fibers holding the lens in place are broken due to any reason, the lens moves out of place freely. This alters the refractive status of the eye and hence develops a double vision.
Other causes include poorly fitted contact lenses, iridodialysis, polycoria, large iridotomies, and retinal disorders like macular edema, central serous retinopathy, retinal detachment, etc.
Causes of binocular double vision
Binocular double vision affects the person when two eyes fail to work together or due to misalignment of the eyes. Common causes of binocular double vision include:
- Orbital disorders such as trauma, tumor, mass or infection
- Extraocular muscle restriction as seen in thyroid-associated ophthalmopathy, extraocular muscle entrapment, mass or tumor, injury or hematoma due to eye surgery
- Extraocular muscles weakness as in mitochondrial myopathies, congenital myopathies, muscular dystrophy
- Stroke, hemorrhage, tumor or mass, trauma, and vascular malformation which cause brain stem injury to cranial nerve nuclei
- Neuromuscular junction dysfunction as in myasthenia gravis
- Third, fourth, and sixth cranial nerve palsies which occur due to ischemia, hemorrhage, tumor or mass, vascular malfunction, aneurysm, trauma, meningitis, and multiple sclerosis.
- A supranuclear injury that occurs due to hemorrhage, stroke, tumor or mass, trauma, multiple sclerosis, hydrocephalus, syphilis, Wernicke’s encephalopathy, and neurodegenerative disease.
Transient diplopia: What causes double vision that comes and goes?
Decompensated phoria, convergence or divergence insufficiency, myasthenia gravis, spasm of accommodation, cyclic esotropia, and superior oblique myokymia causes double vision that comes and goes i.e. Transient diplopia.
Similarly, consumption of various illicit drugs like opioids, benzodiazepines, and medicines used for seizure and epilepsy might also lead to temporary or transient diplopia. Concussions and head injuries may bring the problem of double vision that comes and goes on its own.
It is necessary to seek medical advice if diplopia doesn’t go on its own and if it is accompanied by other vision-related problems.
Double vision test
For both monocular and binocular double vision refraction test, slit lamp test, and dilated fundus examination is to be done to find out the cause. In addition to these routine examinations following tests are done.
Abnormal head posture
Abnormal head postures, head tilt, face turn, and chin up or down are commonly seen in patients with diplopia. It is done to minimize (or maximize) the distance between double images to fuse them or to ignore one image. A comparison of old and latest photographs helps to evaluate the abnormal head postures.
Orbit and lid abnormalities
It plays a vital role in the assessment of diplopia. The abnormal pupillary reaction indicates third nerve palsies due to compression, or ischemic causes. Similarly, examination for fourth and sixth nerve functions plays an important role to pinpoint the cause of extraocular muscle dysfunctions and double vision.
Prism bar test and Maddox rod test are done to gain information about degree and type of ocular misalignment. Likewise, versions and ductions test, Hirschberg’s test, cover test, Krimskey’s test, four prism tests, red-glass test, forced duction test, active forced generation test, and Park’s three steps test is performed in diplopia assessment. Diplopia test, Hess charting and worth four dots test is necessary for any type of diplopia measurement.
Treatment of diplopia
The treatment of diplopia entirely depends on its cause. It can range from refractive error correction, vision therapy, a prism in glasses, contact lenses to surgery, and medications.
Correction of refractive errors
Any type of refractive error should be corrected to make sure astigmatism is not the cause of double image. Eyeglasses, contact lenses, or refractive surgery correct astigmatism double vision.
Selective partial occlusion
It is a new method of treatment. The “spot patch” eliminates the diplopia without compromising peripheral vision. Spot patch is a small round or oval patch made of translucent tape which is placed on the inside of the eyeglass and directly in the line of sight.
It eliminates central vision in the partially occluded eye. As diplopia is a central visual phenomenon, this helps to reduce double vision in the affected eye.
Soft contact lens with dim pupil area
The working principle is the same as that of the selective partial patch. It creates monocular central scotoma suppressing the diplopia with minimal effect on the periphery. This simple, non-invasive method is an effective new tool in the management of double vision.
Patients often complain of double vision while wearing new anisometropic correction glasses due to differential prismatic effects of the two lenses when looking off-center as in reading.
Differential vertical prism affects more than the horizontal. So, in order to improve reading, the vertical prism can be incorporated in the lower portion of the lens to eliminate diplopia while reading.
Fresnel prisms are temporarily applied on the back of the eyeglasses to lower the effect of double vision. Up to 30 prism diopters can be used but the patient will complain of discomfort above 20 prism diopters. The base and apex direction are determined according to the nature of the double vision.
The botulinum toxin (Botox) is applied to the belly of extraocular muscles to weaken the strong eye muscles opposite the weakened one to help balance the eye direction and reduces the effect of diplopia.
Surgical treatment is used to remove cataracts, to fix subluxated or dislocated lens, to correct strabismus, and to correct retinal problems responsible for diplopia.
Eye exercises for double vision
Eye exercises can’t remove diplopia completely but help to reduce the effect of underlying causes. Vergence exercises and accommodative exercises help to improve the condition.
How to cure double vision naturally?
As mentioned earlier, vision therapy, patching therapy, use of prisms and eyeglasses cure double vision naturally. Likewise, adequate supply of the right nutrients, vitamins, minerals, and herbs in the diet can help to restore eye muscle health and eliminate some primary cause of diplopia.
You must quit cigarette smoking and heavy alcohol intake to speed up the healing process of any disorders responsible for double vision. Follow the instructions and follow up schedules given by your doctor to cure diplopia naturally and effectively.