Nystagmus refers to any condition of involuntary eye movement which results in reduced vision. However, since it results in an inability for the two eyes’ line of sight to be in alignment, this classification isn’t completely unwarranted. To call nystagmus a disorder of binocular vision is to use the term very liberally. However, when the head is turned to the left, the person can see more of their left side without having to abduct their left eye.ĭuane’s syndrome is caused by rare genetic variations which result in entire cranial nerves being absent, causing a differential ennervation of the muscles responsible for eye movement. If a person wanted to look off to their left, they would experience double vision, since the left eye would be unable to abduct as it should. To understand why, consider a case of left-eye Duane’s syndrome, in which the left eye has difficulty abducting. The compensatory head posture used to treat this variant of Duane’s syndrome is a turning towards the affected eye. The first variant is the most common, and involves an inability for an eye to abduct, or turn away from the body’s midline. Strabismus is the name given to any misalignment of the eye.ĭuane’s syndrome is a kind of congenital strabismus which affects the horizontal axis, and it comes in three variants. Horizontal deviations in particular are some of the most visible misalignments, and are in fact the most common form of binocular dysfunction. By contrast, some disorders of binocular vision result in a deviation of the eye which is visible. Duane’s syndromeĪlthough superior oblique palsy results in a difficulty in moving the eye in certain directions, it doesn’t typically result in a noticeable misalignment. The head tilt is a classic finding associated with SOP, particularly the congenital kind. The relaxation of the superior oblique muscle of the right eye during a left-shoulder tilt can resolve double vision and also reduce eyestrain. Meanwhile, the superior oblique muscle of the left eye will be activated in order to prevent its extorsion due to gravity. When the head is tilted towards the left shoulder, gravity causes an intorsion of the right eye, so that the superior oblique muscle of that eye will be relaxed. To understand why this occurs, consider a case of SOP of the right eye, which results in the eye having difficulty intorting. The most common symptom of superior oblique palsy is diplopia, or double vision, caused by the misalignment of the two eyes, particularly when a person reads.Ī common compensatory measure found in cases of superior oblique palsy is a head tilt, with the head tilted towards the shoulder of the unaffected side. Although SOP most often results from head trauma, it can also be congenital. Superior oblique palsy (SOP) describes any dysfunction of the superior oblique muscle which is caused by a weakening or complete paralysis of the trochlear nerve. The trochlear nerve is unique in two respects: of all the cranial nerves, it takes the longest path from the brainstem to its target, and it contains the smallest number of neural connections.ĭue to these factors, the trochlear nerve is highly susceptible to damage. The nerve which supplies the superior oblique muscle is called the trochlear nerve, a name which derives from the Latin word for pulley, and it is also the fourth out of twelve cranial nerves. The activity of the superior oblique is threefold: it turns the eye down (depresses), turns the eye out (abducts), and rotates the eye towards the nose (intorts). The superior oblique muscle takes an unusual course, hanging off a small pulley-like ligament before attaching to the upper side of each eye. Superior oblique palsyĮach eye is connected to six muscles which are responsible for moving it around in its socket. The kind of head adjustment depends on the kind of binocular dysfunction. These adjustments, often subtle, can prevent the onset of double vision, a common symptom of binocular dysfunction, but also provide relief from eyestrain. Specifically, disorders of binocular vision, which entail any difficulty in the eyes moving together, are often dealt with by changes in head posture. Unsurprisingly, our body has automatic and largely unconscious mechanisms which compensate for deficits in vision. Vision is undoubtedly our most precious sensory modality, allowing us to recognize objects, navigate our surroundings, and enjoy the many aesthetic qualities provided to us by images and colors.
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