Monocular Elevation Deficiency

Monocular elevation deficiency, also known as "double elevator palsy", is an eye movement disorder in which one eye cannot look upward, or can do so only to a limited extent. The affected eye therefore often sits lower than the healthy eye, which leads to a visible eye misalignment and possibly to double vision.

Causes

The restriction of upward movement can have various causes:

Muscle weakness: weakness of the superior rectus muscle and/or the inferior oblique muscle, which together move the eye upward
Muscle shortening: thickening or shortening of the inferior rectus muscle, which prevents the eye from looking up
Neurological cause: disturbances in the nerve pathways between the brain and the eye muscles

The condition is usually congenital and as a rule affects only one eye. In rare cases it can also develop later in life as a result of neurological damage.

Symptoms and associated findings

The affected eye cannot look upward, or can do so only incompletely
The eye misalignment is particularly noticeable on upward gaze
An abnormal head posture is frequently present: the child raises the chin in order to see better with the lower-sitting eye
Ptosis (a drooping upper lid) occurs in many of those affected
In rare cases a Marcus Gunn phenomenon appears, in which the upper lid lifts on chewing or with jaw movements (so-called "jaw winking")

Diagnosis

The diagnosis is made through a thorough ophthalmological and orthoptic examination. Eye movements are tested in all directions of gaze in order to establish which muscles are affected. Additional imaging such as MRI can help to rule out a neurological cause.

Treatment

Treatment depends on the cause and the severity:

Observation: where the condition is mild and there is no amblyopia, a waiting approach can be taken at first
Amblyopia therapy: if the affected eye develops reduced vision, occlusion treatment (patching the stronger eye) is necessary
Prism lenses: can compensate for double vision in certain directions of gaze
Eye muscle surgery: where there is a marked misalignment or a troublesome abnormal head posture, surgery can improve the eye position. Depending on the findings, the overly tight muscle is loosened or the overly weak muscle is strengthened

Prognosis

Monocular elevation deficiency is generally stable and does not worsen. With targeted treatment, the eye position and any abnormal head posture can be improved considerably in many cases. Regular ophthalmological check-ups are important in order to detect and treat amblyopia early.