human eye

1. The Human Eye

2. The Human Eye
 Refractive index of lens
different for each
wavelength (colour)
 Cool colours (blues)
appear closer; warm
colours (reds) further
away
 Agree?

3. Most people see the red,
Closer than the blue.
Others see the opposite.
How about you?

4. The Human Eye
 Your eyes are about to get a workout. Have
you stretched your eye muscles yet?
 No? Then do that now!

5. Are you seeing spots?

7. Look at the cross for 10 seconds. What do you see?

8. Are these lines
bent….?

9. …or straight?

10. What shapes do you see?

17. Reading What is wrong with
with this sentence?
Aoccdrnig to rscheearch at Cmabrigde
Uinervtisy, it deosn't mttaer in waht oredr the
ltteers in a wrod are, the olny iprmoetnt tihng is
taht the frist and lsat ltteer be at the rghit pclae.
The rset can be a toatl mses and you can sitll
raed it wouthit a porbelm. Tihs is bcuseae the
huamn mnid deos not raed ervey lteter by istlef,
but the wrod as a wlohe.

19. Do you see the rabbit or the duck?

20. Read This Out Loud.

21. Are You Sure? Read again.

23. The Human Eye

24. Structure & Function
 IRIS
 coloured part of eye
 controls light entering
 PUPIL
 black hole in iris
 where light enters

25. Structure & Function
 SCLERA
 whites of the eye
 supports eyeball
 provides attachment
for muscles
 LENS
 converging lens
 allows us to see
objects near and far

26. Structure & Function
 CORNEA
 transparent bulge over
pupil
 focuses light (refracts)
onto retina
 RETINA
 internal membrane
 contain light-receptive
cells (rods & cones)
 converts light to electrical
signal

27. Blind Spot
 On retina where optic
nerve leads back into
the brain
 No rod or cone cells
 Other eye compensates
for this area
 Try this test to prove
you have a blind spot…

28. Close left eye and approach screen while
staring at the letters…watch the dot!

29. Structure & Function
OPTIC NERVE
 Transmits electrical
impulses from retina to
the brain
 Creates blind spot
 Brain takes inverted
image and flips it so we
can see

30. Structure & Function
 RODS
 120 million cells
 detect brightness
(black & white)
 for night vision
 CONES
 6 million cells
 detect colour (RGB)
 GANGLION CELLS
 Detect movement and
patterns

31. Normal Eye Focus
“Blind spot”

32. Video
 YouTube
“The Human Eye” and “How the Human Eye
Works”

33. Focusing Problems
HYPEROPIA
 Far-sightedness
 Problem seeing close
objects
 Distance between lens
and retina too small
 Light focused behind
retina
 Corrected with
converging lenses

34. Far-Sighted (Hyperopia)

35. Focusing Problems
PRESBYOPIA
 Form of far-sightedness
 Harder for people to
read as they age
 Lens loses elasticity
 Corrected by glasses
with converging lenses

36. Focusing Problems
MYOPIA
 Near-sightedness
 Problem seeing objects
far away
 Distance between lens
and retina too large
 Light focused in front of
retina
 Correct with diverging
lenses

37. Near-Sighted (Myopia)

38. Diseases of the Eye
ASTIGMATISM
 Eye cannot focus an
object’s image on a
single point on retina
 Cornea is oval instead
of spherical
 Causes blurred vision
 Some types can be
corrected with lenses

39. Diseases of the Eye
GLAUCOMA
 Group of diseases
 Affects optic nerve -
pressure
 Loss of ganglion cells
 Gradual loss of sight
and eventual blindness
 Check eyes regularly
 Can be treated

40. Diseases of the Eye
CATARACTS
 Clouding forms in lens
due to denaturing of
lens protein
 Obstructs passage of
light
 Caused by age, chronic
exposure to UV, or due
to trauma
 Removed by surgery

41. Vision Correction
CONTACT LENSES
 Artificial lens placed
over cornea
 Same as glasses
 Corrects for both near
and far-sightedness
 Also used for cosmetic
purposes (eye colour,
Hollywood)

42. Vision Correction
LASIK
 “Laser Assisted In Situ
Keratomileusis”
 Refractive surgery
using laser
 Corrects near and far-
sightedness and
astigmatisms