Acquired esotropia is a condition in which one eye deviates inward while the other eye remains normal. This condition is more commonly called crossed eyes. This can cause a double vision, blurred vision, eye fatigue, and headaches. It is often corrected by wearing bifocals, but it's important to determine if Chiari 1 malformation is the cause of the condition. Here's what you need to know.
Chiari 1 Malformation
Researchers have found that acquired esotropia may be a sign of Chiari 1 malformation, which is a defect in the base of the skull that causes the cerebellum at the base of the brain to move or herniate into the opening for the spinal cord. The herniation can put pressure on the brain stem, which can cause a wide range of symptoms throughout the body depending on which nerve is affected.
Nerves that Control Eyes
There are three nerves in the brain stem that control eye movement: the oculomotor, trochlear, and abducens nerves. A Chiari malformation can put pressure on one or more of these nerves, which could damage them and cause them to no longer control the eyes. You can think of the pressure that is placed on the nerves as having a tourniquet affect.
These nerves work together to allow the eyes to focus and work together through accommodation and convergence. Accommodation is the term used to describe how the eyes focus. Convergence is when the eyes align together to focus on nearby objects. When accommodation and convergence don't work right or become imbalanced, such as when any or all of the nerves are damaged by Chiari, it causes the eyes to cross.
Treatment for Acquired Esotropia Due to Chiari
As with any part of the body that has undergone a tourniquet-like condition, the damage to the effected nerves may be permanent. Therefore, you'll need to continue to get treated by your ophthalmologist. Typically, bifocal glasses are prescribed to treat esotropia.
Bifocals assist the eyes in realigning correctly by focusing the affected eye, essentially letting the bifocals do the work so the eye that deviates can relax. This effectively gets both eyes to work together by balancing the imbalanced accommodation and/or convergence.
An easy way to understand this is to think of the crossed eye as an injured leg and the bifocal lens as a crutch. Using a crutch for an injured leg helps to prevent limping in a similar way that using bifocals helps prevent crossed eyes.
Other Symptoms of Chiari
The main symptom of Chiari is a headache at the back of the head, with the feeling of pressure. However, it's important to understand that with the cerebellum in the opening for the spinal cord, the flow of the spinal fluid can be blocked. Spinal fluid cushions the brain and the spinal cord within the spinal canal. Without an adequate supply and flow of spinal fluid, permanent nerve damage can occur, which can range from tingling and numbness in the extremities to complete paralysis. Therefore, it is crucial for you to get checked to see if you have Chiari.
Treatment for Chiari
The treatment for Chiari is called posterior fossa decompression, which is considered brain surgery. In this surgery, more space is created at the base of the brain to allow the cerebellum more room so it no longer puts pressure on the brain stem. Due to this, it can effectively improve esotropia if Chiari is the reason it developed. You and your ophthalmologist will need to consult with a neurosurgeon to determine if you have Chiari, which is typically found through an MRI of the head and neck.