Cardinal Eye Disease

We all have six cardinal positions of the eye. These are the positions in which a normal eyeball can turn. Cardinal Eye Disease refers to the diseases which are caused when the extraocular muscles that hold the eyeball in its position become weak and cause the cardinal positions of the gaze to shift, causing aberrations in sight and other problems in the eyes. Those suffering from the cardinal eye disease, have trouble shifting their gaze and focusing intently on objects that they desire to see.

Cardinal Positions of Gaze

• In all, there are six cardinal positions of gaze. These are essentially six positions in which the gaze can rest, aided by the six extra ocular muscles. These six cardinal positions are:
  • up/right
  • down/right
  • up/left
  • down/left
  • right
  • left
  Each of these positions of the gaze is aided by a muscle which is the primary mover of the eye. Each of these muscles is in turn yoked to the same muscle in the other eye. It is because of this reason that we cannot move our eyes independent of each other.

The Extraocular Muscles

• The extraocular muscles are very small in size. However, they are extremely flexible and strong. These six extraocular muscles help in rotating the eye in the horizontal, vertical and antero-posterior directions on the axes. These muscles are the Superior Rectus, Inferior Rectus, Medial Rectus, Lateral Rectus, Superior Oblique and Inferior Oblique. The rectus muscles help move the eyes in the horizontal and vertical positions, whereas the oblique muscles help move them in the diagonal directions.

Movement of the Eyes

• Each of the extraocular muscles is attached to a cranial nerve. These nerves and the muscles together form a conical orbit in which the eyeball is nestled. It is this formation of the muscles and the nerves that allows the eyes to move on different axes. When the eyes move, we are able to see in different directions without moving our head or the rest of the body. Since each of the muscles is yoked to the muscle of the other eye, the eyes never function independently, except in cases where this yoke is not proper and the eyes become independent of each other.

What Happens in Cardinal Disease

• In a normal eye, both the eyes focus on an object together, and the lines of sight intersect. The intersection casts the image of the object upon the macula of each of the eyes. Here the brain helps in merging the two images into one. However, if the extraocular muscles become weak or damaged due to diseases like glaucoma or damage to the cranial nerves, the eyes no longer remain aligned and a squint is caused in the eyes.

Treatment

• The treatment methods include orthoptics and optometric vision therapy. In these therapies, the eye muscles are trained so that they become stronger and visual clarity is more. Vision therapy also involves improving the neurological control of the movement of the eyes. The ultimate aim is to improve the yoke of the two identical muscles in the socket of each eye, so that the coordination between the two eyes is improved and their movement becomes independent.