1. The Eye
Part 1: Structure and Function

2. Anatomy of the Eye
cornea
sclera
retina
fovea
pupil
iris
optic nerve

3. Step 1
Light rays pass through the clear cornea, which focuses them through the pupil.

4. The size of the pupil can be changed..
This is done by a ring of muscles called the iris, which surround the pupil.
The color of the iris muscles vary, which gives people different eye colors.

5. Pupil closes - constricts
Dim Light
Bright Light
Iris muscles contract
Iris muscles relax
Pupil opens - dilates
Pupil closes - constricts
Lets in more light
Lets in less light

6. SEM – Iris Muscles

7. Step 2
Light passes through the lens, which further focuses the light rays onto the retina.

8. The thickness of the lens can be changed.
The lens can become thicker or thinner, depending on how far away an object is.
This is done by ciliary muscles that pull the lens from above and from below.

9. Distant Objects
Muscles contract
Lens pulled thinner
Focus shifts back
Near Objects
Muscles relax
Lens made thicker
Focus shifts forward

10. Step 3
The light rays hit a layer of specialized light-sensitive cells in the retina.

11. The retina is a layer of specialized cells at the back of the eye.
It contains photoreceptor cells called rods and cones that detect light.
Rods and cones detect different information about the light that hits them...
Rod Cell
Cone Cell

12. Rods and Cones Cone Cells Rod Cells At the center of the retina
3 types: red, green & blue
Detect color of light
Rod Cells
At the edges of the retina
Only black & white
Detect brightness of light

13. The fovea is a dip in the centre of the retina.
Cones are concentrated in the fovea; most of our color vision occurs here.

14. The fovea is a dip in the centre of the retina.
Rods found at the edges
Cones concentrated at the fovea

15. From Eye to Brain Your brain “sees” differently than your eye!
The optic nerve from the left eye connects to the right side of the brain, and vice versa.
So, your brain “sees” everything reversed and then switches it again!

16. Summary: How We See
Light rays enter the eye through the cornea, a convex lens that focuses the light slightly.
They pass through a hole in the eye, called the pupil, which is controlled by a ring of muscles called the iris.
The light passes through the lens, which further focuses the light rays onto the retina.
The retina is a layer of light-sensitive cells: cones for color and rods for brightness
The rods and cones send electrical impulses to the brain along the optic nerve.
The brain interprets the signals as visual images.

17. Any Questions?

18. Quiz - Anatomy of the Eye2 1 5 7 4 3 6

19. Quiz - Anatomy of the Eye
1. cornea
2. sclera
5. retina
7. fovea
4. pupil
3. iris
6. optic nerve