Eye Structure and Function Guided NotesName: ______

Do Now

Which ‘fact’ is false?

1) Your eye muscles are the most active muscles in your body.

2)Newborns don’t produce tears

3)Corneal scratches heal in about 48 hours.

4)If you sit too close to a TV , computer, or tablet, you will damage your eyes.

External Eye and Accessory Structures

______ are the membranes the line the eyelid and eyeball.

______inflammation of these membranes, caused by irritants, allergies, or infection (e.g. “pink eye”).

Extrinsic Eye Muscles

Control movement of the eyes. Remember: rectus = straight, oblique = slanting

Eye muscle names and actions

Name / Action
Lateral rectus
Medial rectus
Superior rectus
Inferior rectus
Inferior oblique
Superior oblique

Eyeball

The eye has three ______, or coats.

•______– “whites of the eye” , outermost, thick connective tissue.

•______– has blood vessels, middle layer

•______– contains the photoreceptors (rods & cones), inner layer

The eye is divided into two fluid-filled chambers:

•The anterior chamber is filled with ______

• The posterior chamber is filled with ______

• Both fluids ______, and the aqueous humor ______.

______occurs when the aqueous humor doesn’t drain properly, resulting in increased eye pressure and blindness

Pathway of Light

  1. Light enters the eye at the ______– a clear, hard part of the sclera.

Functions: protects eye and focuses light

Fun fact: the cornea is responsible for ~70% of the eye’s focusing ability

  1. Light passes through the ______which is the opening in front of the lens.

•The size of the pupil is controlled by the muscles of the ______(the colored part of the eye).

• The pupil dilates or contracts to vary the amount of light hitting the retina.

  1. The light passes through the ______which focuses the light onto the retina.

•The______are muscles which change the shape of the lens to focus on nearby items, a process called ______.

  1. The light passes through the ______to land on the retina, which contains the photoreceptors.

There are no photoreceptors on the ______, which is where the optic nerve exits the eye – this causes a small blind spot.

Photoreceptors

Rods

• more abundant

• sensitive to ______

• do not discriminate ______

Cones -______

•3 types, ______

•triggering of more than one cone isinterpreted by brain as different colors

e.g. if both red and green are activated, the brain will interpret the light as yellow or orange

•______than cones

•mostly found in ______

Responsible for color and fine detail vision – including reading

Refraction and Accomodation

Light is bent – or ______– by nearly every eye structure that it passes through on the way to the retina.

However the lens is the only structure that can vary how much the light is bent in order to allow us to focus on different objects – a process called ______.

As we get older, our lens loses elasticity – making it harder to focus on nearby items.

This condition is called ______(old eyes)

Refraction flips and reverses the light rays, forming an upside down and reversed image on the retina … but the brain learns to interpret visual information correctly.