Today’s guest blogger is Dr. Samantha Slotnick.  Dr. Slotnick, is a Behavioral Optometrist practicing in Hartsdale, NY.   She is also an Adjunct Assistant Research Professor at the SUNY State College of Optometry in NYC.

Eye turns are a common problem affecting about 3% of the population.

Often, when patients with eye turns come to me, they are not aware of any non-surgical options to address their problem. Some of these patients have already had surgery, perhaps unsuccessfully, or they report that the surgery worked for a while, but “didn’t hold.” They’ve often been told in advance that they may need a second or third surgical procedure.

The problem with treating an eye turn (strabismus) with surgery alone is that strabismus is rarely a “muscle-only” problem. Especially after years of living with the eye turn, our highly adaptable brains come up with strategies for coping with information coming from two eyes which do not point in the same direction.

Among these strategies are suppression and anomalous projection (or anomalous correspondence).

Suppression blocks out information from one eye, which protects the person from experiencing double vision.  Suppression only occurs when both eyes are open.  It takes energy to actively suppress information.

Anomalous projection (or anomalous correspondence) trains the brain to match up information between the two eyes based on the way they are pointing, rather than on the way the original connections are made between the eyes and the brain. This allows the patient to retain some degree of stereopsis. (Stereopsis is 3-D vision derived from the two eyes seeing the world from slightly different vantage points.)

These two main “strategies” are very helpful for the person with an eye turn … until attempts are made to straighten the eyes.  If surgery is used to straighten the eyes (by relocating muscle attachments), but no attention is paid to the brain’s “strategies,” there is a much lower potential for long term success.

Consider what would happen if the eyes were made to align (surgically), but suppression continued to block information coming from one eye. In many cases, without addressing this protective “strategy,” the brain does not learn to combine the information from both eyes. So, even though surgery moves the eyes so that there will be no conflict between the images from the right and left eyes, there is also no “glue” to keep the eyes aligned after surgery.  In a case like this, the eyes may start to turn again, even after appearing like they were holding straight after surgery.

Now consider what would happen if the eyes were made to align (surgically), but anomalous projection continued to match up information between the two eyes based on the way they had been positioned for years up until the surgery.  In many of these cases, the patient begins to see double after the eyes have been re-positioned.  Even worse, these patients may experience visual confusionVisual confusion is the appearance of two different objects overlapping, as if they come from the same place. The brain now has the same two main options for avoiding visual confusion: suppression and anomalous projection.  Since anomalous projection worked successfully before, these patients may learn to re-assign information based on their new eye positions.  But without the guidance of vision therapy, many of these patients re-establish their eye turn to the same position that their eyes held before the surgery.  Some patients even end up with the eyes switching to turn the opposite way after surgery!

Vision therapy for patients with an eye turn is a rehabilitation process which helps the brain adapt to a change in the relative positions of the eyes.  It trains the brain to make use of information coming from two directions, and to marry the pieces of information into a single image.  It also trains the brain to be flexible in coordinating the eyes over a range of distances and demands.

Ideally, vision therapy for eye turns should be addressed BEFORE surgery is attempted.  Sometimes, successful vision therapy negates the need for strabismus surgery.  Other times, vision therapy prepares the brain so that surgery is successful and will hold.  If surgery is performed, vision therapy should also be conducted AFTER surgery to help stabilize the visual system and maximize the positive outcome.  It takes training to learn to see and appreciate the world in 3-D, especially for patients with a long history of an eye turn.  The long term benefits of vision therapy for eye turns include:

-Less energy exerted when reading:

-More energy available for thinking!

-Less loss of place/ skipping lines

-Better sense of spatial organization:

-Improved ability in sports and athletics

-Easier time parking a car

-Better depth perception:

-Greater accuracy in hand-eye coordination

-More enjoyment of the visual world

-Better use of peripheral vision:

-Easier time “seeing the forest while viewing the trees”

For an appreciation of how life can be changed after vision therapy for an eye turn, I strongly recommend reading “Fixing My Gaze,” by Susan Barry. This first-hand account chronicles the life experience of a person who had an eye turn from infancy, had multiple strabismus surgeries, and did not begin vision therapy for her eye turn until the age of 48.