The ability to see is one of our most amazing and complicated senses. Muscles play a very important role in the process of vision, as they are responsible for the movement of the eyes (Figure 1). These muscles, known as the extra-ocular muscles, let you look up, down and sideways. Responding to orders from the brain, they act to aim the eyes so that both eyes look at the same place at the same time, thereby creating a single, clear picture in the brain (fusion).n the brain (fusion).
Anything that makes it difficult for the eyes to aim properly can cause dizziness, headaches, reading difficulty and blurred vision. Some patients with eye muscle problems have only one of these symptoms, while others may have two or more symptoms. With the wide array of symptoms, it is not unusual for these people to have sought help from a number of different types of doctors, usually without adequate relief. Most people would not think that the visual system could be the cause of these symptoms and as a result have not sought help from a vision specialist. One of the most common conditions that can cause these symptoms is Vertcal Heterophoria.
Vertical Heterophoria (VH) is a condition where the two eyes have difficulty keeping in vertical alignment. This can lead to double vision, which the brain does not tolerate. Sometimes one eye is physically higher than the other (Figure 2). Sometimes the eyes are aligned correctly but muscle or nerve abnormalities cause the problem. In some instances, this condition may be caused by head trauma, stroke, or neurological disorders. However, most often this is a condition you are born with (congenital). It may take years before symptoms occur, as the body will do the best it can to try and compensate for these problems.
In order for the brain to create one image from the two eyes (fusion) and avoid double vision, the brain overuses the eye muscles to get the eyes to look at the exact same spot. To accomplish this, the eye muscles will strain to make one eye look up a little more, and the other eye to look down a little more. Over a long period of time, these overused eye muscles become achy and fatigued, precipitating the symptoms of VH. Those suffering from VH frequently experience headaches, usually in the front of the face or in the temples, as well as a feeling of being disoriented, lightheaded or dizzy. As the muscles strain, they become fatigued, causing the image seen by one eye to not continuously overlap the image seen by the other eye. In other words, fusion is no longer continuously maintained. This moving in and out of fusion creates the feeling of dizziness, lightheadedness and a sense of imbalance. Those who suffer from Vertical Heterophoria may also have other symptoms in addition to those of headaches and dizziness. These include:
This condition tends to run in families.
To correct this problem, the optometrist will use the Feinberg Method ® (developed by Dr. Debby Feinberg) to add prism to your glasses. Prism is a way of making the glasses such that the image seen by the eye is moved up or down – whatever is needed to allow for fusion to occur without straining the extraocular muscles. Once this occurs, the headaches, dizziness, blurred vision and other symptoms resolve.