Question

8. Explain the muscles involving eye movements and nerves that innervate them. Explain how you determine eye function (movement) as a health care practitioner when you assess your patients.

What does near sighted and far sighted mean and the physiology of this condition.

Answer 1

There are 6 muscles responsible for eye movement;(extrocular Muscle)

4 Rectus muscle -

1) Medial Rectus, 2) Lateral rectus, 3) Superior Rctus and 4) Inferior rectus

2 Oblique Muscle -

1) Superior oblique 2) Inferior Oblique

Nerve supply of Extra-ocular muscle can be remembered as - Mnemonic- All Extra-ocular muscle are supplied by Occulomotor nerve ( CN-III) except LR6 & SO4.

i.e. Lateral Rectus - VI cranial nerve (Abducent nerve)

Superior aoblique - IV cranial nerve (Trochlear nerve )

Rest 4 muscle - III cranial nerve (Occulomotor)

Determining eye movement function -

Patient is made to sit in front of examiner and asked to focus on the tip of index finger of examiner. Then examiner moves his index finger in all the quadrant in zig zag fasion and subject is asked to follow the finger tip without moving his head.

In normal subjects the movement in all the quadrant are equal in both the eyes.

Near sighted - It is a condition in which objects near can be visualised clearly but object placed far are blurred. Seen in case of myopia.

In this the elongate anterioposteriorly hence parelle beam of light from far object gets focused (focal point) in front retina, hence far obeject appear blurred.

Far sighted - in this object placed near is blurred while object placed at far distance visualised clearly. Seen in hypermetropia.

In this eyeball shortens in anterioposteriorly hence near object are not focused on retina, while the light from far object is focused behind the retina.