Restrictive strabismus is an issue with restrictive motility that has many potential origins and has the potential to result from either mechanical or neurological etiology.
Causes can be genetic, traumatic, hormonal, post-paralytic, or myopathic. The patient can have abnormal ocular deviation, which causes defective movement. In some instances, the patient may have an abnormal position of the head. In other cases, the doctor discovers anatomical changes during surgery
To determine restrictive strabismus, the doctor performs a forced duction test, which can determine whether the restriction in motility is due to neurological disorder or a mechanical problem. The test is performed by numbing the conjunctiva, grasping it with forceps, and moving the eyeball in the direction the motility problems have been observed. It will not be possible to generate passive movement of the eyeball if a mechanical restriction is present.
Underlying problems and forms of strabismus
Restrictive strabismus can include Monocular Elevation Deficiency (MED). MED is the trouble lifting the affected eye from any position of gaze with normal ductions (the movement of a single eye). The patient may struggle with one or more of six possible ductions.
Brown’s syndrome is a rare form of strabismus. Patients have difficulty in raising their eye. The disorder may exist at or before birth or may be acquired. Brown syndrome is caused by a problem with the superior oblique muscle. When the head is upright, the muscles and tendons that surround the eye restrict its movement.
According to Wikipedia, “Brown characterized the syndrome in many ways such as:
Limited elevation in the eye when head is straight up
Eyes point out in a straight up gaze (divergence in up gaze)
Widening of the eyelids in the affected eye on adduction
Head tilts backwards (compensatory chin elevation to avoid double vision)
Near normal elevation in abduction
He concluded that all of these features of Brown syndrome were due to the shortening or tightening of the anterior superior oblique tendon. “
Congenital Fibrosis of Extraocular Muscles (CFEOM) are eye movement disorders that result from the dysfunction of all or part of the third pair of cranial nerves. Individuals affected with CFEOM are typically born with an inability to move the eyes in certain directions and droopy eyelids. In addition, the eyes are usually fixed in an abnormal position.
Thyroid orbitopathy, an issue of orbital inflammation, is the most common cause of restrictive strabismus. Often a result of Grave’s Disease, patients will have vertical or horizontal double vision or both. The patient often has restriction involving most commonly the inferior and medial rectus muscles. Traditional muscle surgery releases the tight muscles.
Acquired third nerve palsy can be a partial or complete palsy, and is diagnosed depending on the affected area. Patients may have their eye positioned downward and outward, unable to move in all directions.
Duane syndrome, also called DRS, is a congenital and non-progressive type of strabismus. The restriction in movement is due to abnormal development of the sixth cranial nerve. Patients with this condition have difficulty in rotating one or both eyes outward (abduction) or inward (adduction). The eyelid position might also change when the patient tries to move their eyes. Duane syndrome is due to miswiring of nerves to the eye muscles. Surgery cannot address the problem of nerves that are miswired but can move muscles to compensate for the miswiring. While surgery cannot completely restore normal eye movement, it will help.
Treatment requires a careful analysis of the patient’s history. Eye position is the major goal of treatment of restrictive strabismus, avoiding muscle resection as possible. Drugs, botox, and surgery are all treatment options.
Amniotic Membrane Transplant for Restrictive Strabismus
Strube et al. (2011) used AMT in patients with restrictive strabismus that followed surgery such as for pterygium, retinal detachment, orbital floor fracture, etc. he seven developed post-operative scarring. They had failed additional standard surgery to remove the adhesions. The patients underwent another surgery using AMT. The surgeons removed restrictive adhesions and placed an amniotic membrane transplant. Strube measured the outcome based on ocular alignment, ductions, symptom relief, and resolution of diplopia. There was improvement of ocular motility in 6 of the 7 patients; 1 patient had recurrence of scarring with persistent diplopia (double vision).
The remaining 6 patients did not have any further scarring, and their eye movement remained stable during the follow-up period. The authors concluded that AMT may be a help in treating restrictive strabismus.