Dr Ben Wild
Overview |
Eye movements are controlled by 6 extra-ocular muscles. The superior rectus (SR) pulls the eye upwards, the inferior rectus (IR) pulls the eye downwards, the lateral rectus (LR) pulls the eye outwards and the medial rectus (MR) pulls the eye inwards. The superior oblique (SO) muscle connects to the eye after passing through a pulley called the trochlea and is mainly responsible for rotating the eye inwards and pushing the eye downwards. The inferior oblique (IO) follows a similar path as the superior oblique, except underneath the eye and does not travel through a pulley system.
Duane retraction syndrome refers to a congenital condition (born like this) where the 3rd cranial nerve, the nerve that controls the SR, IR, MR and IO muscles also controls the LR which is supposed to be under sole control of the 6th cranial nerve. When these two nerve signals fight each other, the eye retracts into the orbit.
Frontal view of a right eye with extra-ocular eye muscles. The highlighted muscles indicate the medial and lateral rectus muscles that battle each other in Duane Retraction Syndrome.
There are 3 main types of Duane retraction syndrome. All 3 types are sometimes unilateral (one eye) but often bilateral (both eyes). Often there are other systemic deficits like external ear abnormalities, speech disorders, skeletal abnormalities.
Type 1 is the most common and occurs when there is no 6th nerve control of the LR muscle but the 3rd nerve has partially grown in its place. This patient cannot abduct the eye (look away) and when trying to do so, the eye retracts. This patient may have a crossed eye.
Type 2 is the least common and occurs when the 6th nerve is intact and present but the 3rd nerve still has some control over the LR muscle. In this case the patient can’t adduct the eye (look inwards). This patient may have a wondering eye.
Type 3 has almost no 6th nerve control and the 3rd nerve equally controls the LR and MR muscle. This patient cannot look left or right and when trying to do so, the eye retracts.
Signs and Symptoms |
Signs
Head turn to reduce possible double vision, difficulty moving the eye out (type 1 and 3), difficulty moving the eye in (type 2 and 3), retraction of eye into orbit.
Symptoms
Usually no symptoms, sometimes patients may notice double vision and pain/tenderness in up and inwards gaze.
Causes and Risk Factors |
Causes
Congenital malformation.
Risk Factors
There are no known risk factors.
Prevention and Treatment |
Prevention
There are no known preventative measures.
Treatments
· No treatment required in most cases.
· Surgery to straighten head posture or for double vision.
Prognosis |
Duane retraction syndrome may restrict a patient’s life in terms of certain career choices (pilot, truck driver, etc.) but is not vision threatening. In most cases the patient suppresses (brain ignores) one eye when the eyes are not aligned to avoid double vision and therefore the patient is unaware of any issue. In some cases surgery is needed to correct any double vision or fix a tilted head posture but surgery does not correct the congenital malformation, just the double vision or head posture.