Double Vision

When people see “Two for One” deals they are generally pretty excited or if you remember the 90's tv commercial for Double Mint Gum, “double your please, double your fun..” you remember the rest! However, double is not always better regardless of that catchy jingle. Diplopia, or double vision, can present in different ways, have varying etiologies, and can be associated with systemic manifestations that can be life-threatening. Double vision can occur with both eyes open but in some cases can occur with only one eye open, this is called polyplopia. Double vision can be intermittent, constant, distinct, or appear more like blurred vision. To be

Eye-care providers who enjoy working with double vision are doctors who have done extensive training following their doctorate work. If someone has a complaint of double vision they should see a provider with residency training in binocular vision, neuro-optometry, or neuro-ophthalmology. It is important to work with someone with this specialized training to ensure the proper testing is done to determine not only etiology but also determine the best course of treatment.

What are some causes of double vision?

1. Strabismus: A strabimus is an ocular deviation where the eyes don't focus on the same point. The eye can turn in-ward (esotropia – visit our blog on esotropia), outward (exotropia – visit our blog on exotropia), upward (hypertropia – visit our blog on hypertropia), and downward (hypotropia). So basically a strabismus can go in any direction, just like the Wonka-vator. Now a strabismus can occur intermittently and be a micro-strabismus, which means not cosmetically noticeable. A strabismus can be congenital, secondary to a systemic event such as an aneurysm, secondary to a traumatic event, secondary to an uncorrected refractive error, etc.

2. Convergence Insufficiency: A convergence insufficiency is a decreased ability for the eyes to turn in-ward together as a team and keep a near object single and in-focus. To look at a near target the eyes must converge together and sustain this inward posture. If the eyes are unable to hold this posture or even converge to the appropriate distance the patient's vision will fluctuate and even double at near. Some symptoms that will accompany can be headaches, eyestrain, and blurred vision. This double vision presents horizontally.

3. Ocular Surface Disease/Corneal Irregularity: Corneal surface disease or corneal irregularity can cause a monocular diplopia (double vision with one eye). This can occur because when light enters our eye the first layer that the light hits is the tear film and then the cornea, if this surface is not smooth the light will refract in different directions. This refraction can cause distorted images and doubling.

4. Cataracts: Just like corneal irregularities, cataracts can cause diplopia because of an improper refraction of light secondary to the opacity. This double vision can also be monocular. In certain circumstances if a patient has had cataract surgery and is utilizing a multi-focal intra-ocular lens implant they may have diplopia depending on the lens design and the patient's pupil size.
    

Are there certain systemic conditions where diplopia is more common?

1. Diabetes: Diabetes can have some serious implications throughout the body as well as the eyes (visit our blog on diabetes). Poorly controlled diabetes can cause a third cranial nerve palsy. This is where the eye turns outward and the lid can droop. The third-nerve innervates some muscles responsible for eye movement as well as the upper eye lid.

2. Myasthenia Gravis: Myasthenia gravis is a chronic autoimmune neuromuscular disease. These patients have muscle weakness that can fluctuate. These patients may see double intermittently as well as have droopy eyelids (ptosis) intermittently.

3. Traumatic Brain Injury: Traumatic brain injuries can cause diplopia because they can induce a convergence insufficiency and/or a cranial nerve palsy.

4. Neuro-degenerative Conditions: Similar to a myasthenia gravis neurodegenerative conditions can have intermittent blurred vision and diplopia secondary to fluctuations in muscle responsiveness.
    

As mentioned before there are a lot of treatment options for diplopia. Regardless of the cause of diplopia a thorough examination is indicated with a residency trained neuro-optometrist or neuro-ophthalmologist to determine the cause and best treatment options. Two is not always better than one!