Square wave jerks are defined as small, horizontal, involuntary fast eye movement that take the eyes off of a target of interest, followed by a short interval (about 250 milliseconds) and a return eye movement back to the target of interest.
In other words, a square wave jerk is a type of eye movement intrusion that interferes with normal gaze holding or tracking of a target.
Square wave jerks commonly occur from the brain’s inability to inhibit or stop certain neuronal networks from being activated, resulting in the “jumping” of the eyes off of the target of interest. Clinically, square wave jerks can be evaluated by ophthalmic evaluation, eye movement testing in darkness, or during volitional eye movement testing.
Square wave jerks are a common disorder that occurs in many conditions, but quite frequently in cerebellar disorders and in post-concussion syndromes.
Many patients that have square waver jerks intrusions experience:
- brain fog
- motion sickness
- visual disturbances
- blurry vision
- balance issues
- difficulties with reading
- light sensitivity (such as on computer or TV screens).
Sometimes, patients can “feel” this eye movement intrusion occurring and sometimes they cannot. It is quite common for people who experience square wave jerks to have them occur fairly frequently, as many as 1-2 intrusions every few seconds.
There are many therapies that are designed to attenuate these eye movement intrusions from occurring. These therapies are targeted for the brain areas involved in this dysfunction, rather than the eyes themselves. In other words, although this dysfunction involves an abnormal movement of the eyes, the therapy that helps correct this dysfunction is not an eye movement therapy, but rather a therapy that is targeting the central brain areas that are dysfunctional causing the square wave jerks to occur.