The eyeball is an instrument that gifts us the ability to see over 7 million colors everyday and boasts a resolution equivalent of about 576 mega pixels. The reason the anatomy of the eye is so fascinating is because the muscles of each and every pair of human eyes are innervated by three cranial nerves (CNs 3, 4 & 6). These innervations enable us to move our eye balls in all directions and allow us to have a binocular visual field of 100° vertical (upward & downward gaze) and 200° horizontal (medial & lateral gaze). The muscles and nerves of both of our eyes are constantly working together. For example, in order to look to the left: CN 6 fires in our left eye causing the lateral rectus muscle to contract, this allows the left eye to move outward or laterally; while this occurs, CN 3 is firing simultaneously in our right eye causing the medial rectus muscle to contract, this allows our right eye to move inward or medially. The result of these nerves working together allows us to look to the left (with the left eye moving laterally and the right eye moving medially).
In my second year of medical school, I remember the mnemonic ‘LR6-SO4-R3’ helped me memorize which cranial nerves innervated which ocular muscles. It literally saved my life in neurology and ophthalmology! The pneumonic stands for: Lateral Rectus muscle (CN 6); Superior Oblique muscle (CN 4); and CN 3 innervates the rest!
In this video provided by our fellow non-profit organization (Seattle Science Foundation), we can integrate the anatomy of the ocular muscles into our discussion of these three cranial nerves. With this in mind, let’s take a second today to be grateful for the priceless gift of vision!
Written by Student Doctor: Navpreet Singh Badesha ©06/14/2017 All Rights Reserved.
Video Narrated by: Joe Iwanaga, D.D.S., Ph.D.
