1. The Human Eye

2. A colossal squid has eyes that can be over 40 cm (more than 1 ft!)
in diameter. That’s 100X larger than a human eye!

3. Comparing the Eye to A Camera

4. How the Human Eye Focuses
The ciliary muscles make the lens shorter & thicker to focus
on nearby objects.

5. Myopia (near-sightedness)
The eye cannot focus on distant objects because the eyeball
is too long.

6. diverging lens

7. The eye cannot focus on nearby objects because the eyeball is
too short.

8. converging lens

9. A condition where the lenses of the eyes become stiff & the ciliary
muscles can no longer make the lenses change shape.
As a result, people with presbyopia cannot focus on nearby objects.

10. If a near-sighted person develops presbyopia, they will need to
wear bifocals.

11. Astigmatism
Blurred vision that is
usually caused by a
cornea that is oval
rather than rounded.

12. LASIK (laser eye surgery) is an alternative to eyeglasses
or contact lenses for patients with myopia, hyperopia, or
astigmatism.
This procedure involves reshaping the cornea with laser light.

13. Night-Vision Devices