The ocular motility test is the assessment of the 12 extraocular muscles and their effect on the movement of the patient’s eyes. The exam seeks to detect restricted or unusual eye movement. It is a preliminary test and a critical part of the comprehensive eye exam. The doctor can also order an ocular motility test when he/she suspects neurologic disease or a patient complains of double vision.
Each eye is attached to six muscles, which enable the eyes to coordinate in their movements. The muscles control the eyes in a complex partnership of protagonist and antagonist teamwork. The muscles work to move the eye left/right, up/down and in tort/excyclotort. It is interesting to note that these muscles have the highest ratio of motor neurons to muscle filament of all the body muscles. It makes possible the excellent motor control and exemplary alignment of the eyes.
Also Known As
- Ocular motility test
- Extraocular movement
- Ocular motility examination
The ocular motility test can be done at the doctor’s office or the eye clinic by:
- A technician
- An optometrist
- An ophthalmologist
The specialist will conduct the test to assess weakness or other disorders in the eye muscles. Problems with eye motility can be symptoms of life-threatening ailments, such as:
- Brain tumors
- Multiple sclerosis
- Myasthenia gravis
- Thyroid eye disease
The doctor will be interested in:
An ocular motility test can help the doctor to establish the cause of diplopia or double vision. It may affect one or both eyes. Health professionals take cases of double vision seriously because it may be a symptom of neurological disorders. Double vision may be caused by damage to the nerves encircling eye muscles, a neuromuscular disorder that causes muscle weakness (myasthenia gravis), Graves’s disease, which is a side effect of hyperthyroidism and strabismus.
The doctor will check if one or both eyes are turned up, down in, or out. It is a characteristic of strabismus. Patients with this disorder are often called wall-eyed or cross-eyed. The disease may be congenital or arise later in life. Strabismus in adults might be due to eye trauma, brain injury (including stroke), or other conditions like diabetes, Graves’ disease, and Guillain-Barré syndrome. It can cause double vision, problems with depth perception and increase the risk of the patient developing a lazy eye or amblyopia.
It is a condition in which the patient’s brain can not process data from one of the patient’s eyes. Amblyopia can occur because one of the patient’s eyes is misaligned and including its signals would cause double vision. The disorder can also arise if one of the patient’s eyes has a more precise view than the other, causing the patient’s brain to select the better image. Amblyopia starts at an early age when the eye is not used well or stimulated and can lead to an irreversible decrease in vision.
Shaking of the eyes
The involuntary, rhythmic wobbling or shaking of the eyes is an indication of a disorder called nystagmus. The wobbling may be vertical, diagonal, or horizontal. Frequently, the disease is congenital and may be a component of other developmental syndromes. In adults, it may indicate brain damage from trauma stroke or infection, vitamin deficiency, excess alcohol consumption, side effects of certain medications or disorders, such as multiple sclerosis and brain tumors. In severe cases, it can impact visual acuity because the eyes are always moving back and forth.
Eye movement accuracy
Overcorrection or under correction of some eye muscles shows that the patient’s eye movement is inaccurate. It could be a symptom of inherited disorders like Duane's retraction syndrome, which is a type of strabismus affecting the horizontal eye movement.
Often, these occur in traumatic injuries like a blow to the eye. Blunt trauma to the bones that form the floor of the eye orbit can blow them out because they are thin. It may cause an eye muscle to get hooked or trapped in the bone.
Cranial nerve palsies
The brain controls movement of the eyes through cranial nerves. Often, the motility test helps the doctor to detect central nervous system disorders.
Preparation & Expectation
The ocular motility test is an easy and quick eye exam that only involves normal eye movements. The patient doesn’t require any preparation before the test and there is no discomfort.
The patient will stand or sit looking straight ahead and hold their head up. The doctor can first visually check the eyes for deviations that may result from Strabismus, or cranial nerves palsy or dysfunction of the extraocular muscle. He/she will then hold an object, usually a pen, about 16 inches in front of the patient’s eyes. He/she will move the object to various sides and ask the patient to follow it with their eyes, without moving the head. The doctor may also conduct a cover/uncover test where the patient looks at a distant target. Then he/she covers one of the patient’s eyes and uncovers it after a few seconds. The test is done for both eyes.
The doctor may further conduct an alternate cover test. The patient stares at a distant target and the doctor covers one of the patient’s eyes and, after several seconds’ shifts the cover to the other eye. The patient keeps staring at the same distant target, no matter which of their eyes is covered. It can take three or four cycles.
The doctor will reveal the results of the test and talk to the patient about any abnormalities that may be found and the treatment options.
The eye movement disorders might be due to muscle abnormalities or problems in the areas of the brain that control the muscles. Eye oscillations could be due to recreational drugs, medications, impaired vision or brain stem disorders. It is essential to detect eye movement disorders early, especially in children, to improve the chances of regaining a better vision.
Treatment of eye movement disorders varies depending on the type of condition and the patient. The doctor will also suggest treatment for any underlying trauma or disease. For examples, in adults with strabismus, the doctor may recommend a series of steps to improve the patient’s vision, including:
- Corrective glasses
- Eye muscle exercises
- Eye surgery to correct the direction the eye points
Risks & Complications
An ocular motility test is safe and has no risks or complications associated with it.