This is one of several hereditary, nonprogressive forms of strabismus (abnormal alignment of the eyes) in which the eye movements are restricted. Although the name implies a disease of the muscles that move the eye, the primary disorder is one of maldevelopment of the nerves that supply those muscles.
This is usually a congenital condition in which the eyes do not move properly beginning at birth. The lids usually appear to droop (ptosis) as well. Often one eye appears to wink when chewing. The eyes may at times look to the side (diverge). Because the eyes may be fixed in downgaze and the lids droop, patients often have to tilt their heads far back in order to look ahead.
Some individuals with this condition lack the normal amount of skin and eye pigmentation.
There have been several reports of parent to child transmission suggesting autosomal dominant inheritance but no specific mutation has been identified.
The diagnosis can be made at birth by a medical eye doctor (ophthalmologist) or a neurologist. Longevity is unlikely to be impacted and vision is normal. In selected individuals surgery on the eye muscles or eyelids can at least partially correct the eye malalignment but it is not possible to restore full motility.