Double Vision

Introduction to double vision 

Double vision is when you see two images of an object when there is only one. The most important observation to make when having double vision is whether it goes away with covering either eye.  If the double vision is present in one eye by itself, this is monocular double vision.  Alternatively, if the double vision resolves completely with closure of either eye, and is only present with both eyes open, this is binocular double vision.

Binocular double vision is caused from the muscles that control the eyes are not functioning correctly. This can be due to a structural problem (the orbit), primary muscle condition, or damage to the brain/nerves that control the muscles of the eye. Binocular double vision can be corrected with prism glasses or strabismus surgery. Prisms bend light, shifting images so that they align. Strabismus surgery is the correction of the malposition eye or eyes by performing surgery on the muscles that control the eyes. Below are a few conditions that can cause adult binocular double vision. 

Sagging Eye Syndrome 

This is a condition where the connective tissues that hold the muscles around the eyes in position starts to loose laxity with age and the muscles start to sag from the loss of usual tension. This laxity causes the muscles to not be able to move the eyes in the correct direction and with the usual force needed which can cause double vision. 

Cranial Nerve Palsy 

There are a total of 12 cranial nerves that originate in the brain to control muscles/sensation of the head. There are 3 cranial nerves that control the muscles of the eyes. Whenever those nerves are damaged in any way it causes the muscles they control to become weak and cause double vision. Sometimes this can be reversible with time but other times treatment with prism glasses or strabismus surgery is needed to resolve the double vision. 

Thyroid Eye Disease(TED)

TED is an autoimmune condition that can affect the muscles of the eyes and/or the fat in the eye socket. It is most commonly due to hyperthyroidism but it can also be caused by hypothyroidism. TED causes the muscles and fat of the eye socket to swell. When the fat swells it causes bulging of the eyes forward. When the muscles swell it causes them to become tight and not able to move. The muscles are not always equally affected and that causes the eyes to become misaligned and creates double vision. 

Once someone has their thyroid hormones under control with medication or thyroid surgery there can be some improvement in symptoms. Depending on how severe the ocular misalignment is this can be treated with prism glasses or strabismus surgery. Strabismus surgery is not performed until thyroid levels are stabilized. Due to hyper or hypo-thyroidism is a chronic disease ocular symptoms can reoccur and cause surgery to need to be repeated. 

Myasthenia Gravis (MG)

As previously discussed MG is caused by an autoimmune condition that affects the muscles of the body that results in muscle weakness. When ocular MG occurs, this can cause double vision as it can make some muscles of the eye weaker than others. When this happens it throws off the balance of the eyes and causes double vision. Medical treatment is usually all that is needed for treatment.  

Strabismus Surgery 

Strabismus surgery is most often performed on children as a lot of kids are born with a “lazy eye”.  The misaligned eyes need to be corrected by a certain age for their vision to develop normally. Sometimes if the condition isn’t corrected as a child or you develop a condition later in life that causes ocular misalignment strabismus surgery can be needed for adults as well.

The surgery is done in an outpatient setting, meaning no hospital stay is usually required. The eyes do not require patching after the surgery. If a patient had prism glasses prior to surgery they will need new updated glasses without prisms after the surgery to allow for the brain to adapt. There is a chance of continued double vision within the first few months of surgery but this usually resolves after the brain adapts. Sometimes temporary prisms are needed to assist patients in the initial post-operative period to help with continued double vision. It can take up to 3 months for patients to be fully healed from surgery.