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Anatomy of the Eye
Anatomy of the Eye
Clinical Pearls
OD: Means right eye (oculus dexter)
OS: Means left eye (oculus sinister)
OU: Means both eyes (oculus uterque)
External Ocular Muscles
Superior Rectus: Moves eye superiorly (up)
Inferior Rectus: Moves eye inferiorly (down)
Medial Rectus: Moves eye medially (in towards nose)
Lateral Rectus: Moves eye laterally (out)
Superior Oblique: Moves eye down & out ("cheaters muscle")
Inferior Oblique: Moves eye up & out ("birdwatchers muscle")
LR6, SO4, R3
But what does this mean??
(LR) Lateral Rectus: Innervated by CN 6 (Abducens nerve)
(SO) Superior Oblique: Innervated by CN 4 (Trochlear Nerve)
(R3) "All the rest": Innervated by CN 3 (Oculomotor Nerve)
Note:
Some patients can develop Diplopia (double- vision) due to an imbalance in their eye muscles because now each eye will point in a different direction!
Arteries
These take oxygenated blood from the heart to a target organ
Veins
These take deoxygenated blood from an organ back to the heart
Think of the eye as a sandwich. You have multiple layers and structures on top of one another from front to back
Even if only one of these layers is damaged, your vision will be affected
Retina Basics
Retina Basics
This is called a Fundus Photo (AKA: Optos).
It is an actual photograph of the retina looking at it from above
It takes an image of the entire retina
The fundus refers the the inner back part of the eye as a whole (retina, optic nerve, and vessels)
Optic Nerve (blue circle)
This transmits light from the retina to the brain
This is what gets damaged by Glaucoma
You will have a natural blind spot in this area as there are no rods/cones here!
Macula (green circle)
This is where the lens focuses your vision
The macula represents 80% of your overall vision and solely responsible for your central vision
This is what gets damaged by Macular Degeneration and other retinal diseases
Note:
The optic nerve is ALWAYS closer to your nose when looking into the eye. You can tell you are looking at OD or OS this way, even if the images are mislabeled
You can also remember it this way: for OD, the optic nerve will always be to the right of the Macula. For OS, the the nerve will be to the left of the Macula
This is called an OCT (Optical Coherence Tomography)
An OCT is a different type of retinal image done with a laser
It takes an image of a very small part of the retina
It looks at cross sections of the retina and you can see all the individual tissue layers throughout it
This is the macula as seen on an OCT image
The center of this dip is the Fovea Centralis (absolute center of the macula with the highest visual acuity)
When looking at the Macula, we always take 2 images per eye but on different settings
This is what the OCT analysis look like
Certain diseases can affect the health of the macula, such as age related macular degeneration (AMD)
Here is what your vision would be like with AMD
You would have to look off- centered to see people's faces!
Blind Spot Test
Cover your left eye
Look at the plus symbol on the left
Move closer to the screen until the black circle on the right disappears
At this distance, the black circle is right over your optic nerve which has no photoreceptors, and hence, you cannot see it anymore!!
Self Test
Self Test
Where is the Cornea and what does it do?
What does the Crystalline Lens do?
Name the 2 types of fluid inside the eye. Where are they located in the eye?
What is the pupil?
What is the name of the muscle that regulates the amount of light coming into the eye?
What does OU mean? OD? OS?
What is an OCT?
What does an artery do?
What does a vein do?
What is the part of the retina that accounts for your central vision? What disease primarily damages this structure?
What is the Fundus?
True of false: If you were looking into the left eye the optic nerve would be to the right of the Macula
What part of the eye transmits light from the retina to the brain? What disease primarily damages this structure?
10) True or false: This is an image of OD (explain your thought process)
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