Clinical Testing
of the Eye
Introduction
During the clinical testing of the eye movements, the aim is to test the movements of the individual extraocular muscles. In order to do this, the gaze has to be lined up to the plane of the muscles that are being tested.
Testing the muscles individually also allows the nerve supply to each muscle to be tested.
In this resource you will find a series of interactive 3D models that will help you understand how the muscles are tested, as well as some introductory models.
You can click and drag on the model to rotate, use the mouse wheel to zoom in and out and click on the annotations to learn more about each structure.
Contents
Bones of the orbit
The orbit is formed by six bones: frontal, maxilla, zygomatic, sphenoid, lacrimal and ethmoid. The orbits have a pyramidal shape with a roof, floor, medial wall and lateral wall.
The apex of the pyramid is directed posteromedially. The nasal bones and inferior nasal conchae, which are not part of the orbit, are also shown in the model.
Axes of the eye and orbit
The eyeballs are directed anteriorly, as shown by the blue arrow. In contrast, the axis of each orbit, as shown by the green arrow, is directed slightly laterally from back to front.
This is relevant to clinical testing because in order to isolate the movements of the superior and inferior rectus muscles, the axis of the eyeball has to be aligned with the axis of the orbit. That explains why they have to be tested with the eye abducted.
Extra-ocular muscles
There are seven extra-ocular or extrinsic muscles. The superior, inferior, medial and lateral rectus and the superior and inferior oblique move the eyeball. The levator palpebrae superioris, which lifts the upper eyelid, is not shown in this model.
The superior, inferior and medial rectus and the inferior oblique are innervated by CN III (oculomotor nerve). The superior oblique muscle is innervated by CN IV (trochlear nerve), and the lateral rectus muscle is innervated by CN VI (abducent nerve).
Eye movements
Note: to name the movements, take into account that the model represents the right eye
It is also important to remember that, while these are the movements involved in the clinical testing, other combinations of movements are possible and some muscles have more than one action.
Abduction
The lateral rectus muscles abducts the eye. That is its only action. It brings the axis of the eyeball in line with the axis of the orbit and also with the superior and inferior rectus muscles. Innervation is provided by CN VI (abducent nerve).
Abduction and Elevation
Abduction has already occurred. The lateral rectus muscle keeps the eyeball looking laterally where its axis is in line with the axis of the orbit and the superior and inferior rectus muscles. During clinical testing, the superior rectus muscle elevates the eye when the eye is already abducted. Innervation of the superior rectus is provided by CN III (oculomotor nerve).
Abduction and Depression
Abduction has already occurred. The lateral rectus muscle keeps the eyeball looking laterally where its axis is in line with the axis of the orbit and the superior and inferior rectus muscles. During clinical testing, the inferior rectus muscle depresses the eye when the eye is already abducted. Innervation of the inferior rectus is provided by CN III (oculomotor nerve).
Adduction
The medial rectus muscle adducts the eye. It is its only action. It brings the gaze into the same plane as the superior and inferior oblique attachments.
Adduction and Elevation
Adduction has already occurred. The medial rectus muscle has caused the eyeball to look medially, where its axis is in line with the superior and inferior oblique muscles. During clinical testing, the inferior oblique muscle elevates the eye when the eye is already adducted. The inferior oblique is innervated by CN III (oculomotor nerve).
Adduction and Depression
Adduction has already occurred. The medial rectus muscle has caused the eyeball to look medially, where its axis is in line with the superior and inferior oblique muscles. During clinical testing, the superior oblique muscle depresses the eye when the eye is already adducted. The superior oblique is innervated by CN IV (trochlear nerve).