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

The Human Eye
Comparing human eye to camera
Hyperopia, Presbyopia & Myopia
Components of the Eye
Iris
Pupil
Iris
Pupil
Eye
Camera
equivalent
Function
Iris
Diaphragm
Controls amount of light
Aperture
Where light enters the
eye
(coloured part)
Pupil
(hole in iris)
Components of the Eye
Iris
Pupil
Cornea
Eye
Lens
Camera
equivalent
Cornea &
Converging lens
Lens combo
Function
Refraction of light
(mostly in cornea)
Focuses light
Components of the Eye
Retina
Iris
Pupil
Cornea
Lens
Eye
Camera
equivalent
Function
Retina
Film or
digital sensor
Light sensitive cells
convert light signals to
electrical signals
Components of the Eye
Retina
Iris
Pupil
Optic
Nerve
Cornea
Lens
Eye
Optic nerve
Camera
equivalent
Function
Electrical signals are
passed through to the
brain
Components of the Eye
Image formed on retina will be smaller & inverted.
You “see” with your brain
Your brain will “flip” the image
Eye Accommodation
Ciliary muscles can change the shape of the lens
slightly to accommodate focusing on distant &
nearby objects.
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)
Presbyopia
Also problem on seeing nearby objects.
HOWEVER, this is due to aging  because lens
lose their elasticity.
Solution: Corrective converging lens.
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)