1. The Human Eye Comparing human eye to camera Hyperopia, Presbyopia & Myopia

2. Components of the Eye Eye Camera equivalent Function Iris (coloured part) DiaphragmControls amount of light Pupil (hole in iris) ApertureWhere light enters the eye Iris Pupil

3. Components of the Eye Eye Camera equivalent Function Cornea & Lens combo Converging lensRefraction of light (mostly in cornea) Focuses light Iris Pupil Cornea Lens

4. Components of the Eye Eye Camera equivalent Function RetinaFilm or digital sensor Light sensitive cells convert light signals to electrical signals Iris Pupil Cornea Lens Retina

5. Components of the Eye Eye Camera equivalent Function Optic nerve Electrical signals are passed through to the brain Iris Pupil Cornea Lens Retina Optic Nerve

6. Components of the Eye Image formed on retina will be smaller & inverted. You “see” with your brain Your brain will “flip” the image

7. Eye Accommodation Ciliary muscles can change the shape of the lens slightly to accommodate focusing on distant & nearby objects.

8. Hyperopia (Far-sightedness) Problem focusing on nearby objects. Due to either: a)Distance between lens & retina are too small b)Focusing power of cornea-lens combination is too weak  light is focused behind the retina Solution: Corrective converging lens (or positive meniscus)

9. Presbyopia Also problem on seeing nearby objects. HOWEVER, this is due to aging  because lens lose their elasticity. Solution: Corrective converging lens.

10. Myopia (Near-sightedness) Problem focusing on distant objects. Due to either: a)Distance between lens & retina are too large b)Focusing power of cornea-lens combination is too strong  light is focused in front of retina Solution: Corrective diverging lens (or negative meniscus)