Keywords for lecture 1 electromagnetic spectrum, (pit viper), mechanical energy, chemical energy, stages of vision, (i) eye movements,
(ii) focus, (iii) light regulation, pupil, pin-hole camera, refraction, focus, cornea, lens, accommodation, myopia, hyperopia, astigmatism, presbyopia

Eye movements
Point eyes to right place
Accommodation focus
Pupils
Light
Adaptation
Adjust for the light level
Transduction
Convert light energy to activity in cells

DISTANT
OBJECT eg. star
Even the relaxed lens is too strong. The rays are focused in front of the retina!
DISTANT
OBJECT eg. star
The CONCAVE lens makes the rays DIVERGE, thus compensating for the unwanted strength of the eye's optics.
The eye and its optics 4 - 5

LONG SIGHTED
(Hyperopia)
CLOSE
OBJECT
The fully-contracted lens cannot get strong enough. The rays are focused behind the retina!
CLOSE
OBJECT
The CONVEX lens helps the rays CONVERGE, thus assisting the inadequate strength of the eye's optics.
The eye and its optics 4 - 6

With age, the lens becomes less flexible and accommodation becomes fixed at some distance. This fixing of the focal length of the lens is called PRESBYOPIA .
The refracting power of the eye may not be the same in all dimensions.
This is called ASTIGMATISM .
Side view
Top view
For this person, the cornea is flatter from left to right than it is from top-to-bottom. Therefore, for this astigmatic person, vertical lines would be better in focus than horizontals.

Photo taken through a LARGE aperture shallow depth of field
(only one distance is in focus)

Photo taken through a SMALL aperture long depth of field
(lots of distances are in focus)

Most of the refraction takes place at the air/water boundary of the CORNEA in the air
No refraction takes place at the water/water boundary of the CORNEA in the water
Lens in the eye of an AIR-LIVING animal
AIR LIVING
Lens in the eye of a
WATER-LIVING animal
WATER LIVING

DIVING ANIMALS
1 put on a mask that keeps air in front of cornea
2 rely on a STRONG lens that can change from air-living to water living eg: otter
3 Have a FLAT cornea (to remove its influence) and then use a WATER-LIVING style lens eg. Penguin, flying fish
4 Have two pairs of eyes - one for each environment eg. Four-eyed fish
5 Use a WATER-LIVING style lens in the water and bi-pass the cornea by using a
PIN HOLE pupil on land eg. seal
Air Type
Water Type

1. Diving mask

2. strong
… Air Type
The Otter - who can change her eye from .....
… to…. ….Water Type

3. Flat cornea + fish-type lens

4. Four eyes (!)
Four-eyed fish

4. Four eyes (!)

5. Pin hole on land; fish-type in water

Human using the seal solution

Antony van Leeuwenhoek (1632-1723)

Leeuwenhoek’s
Microscope

Na +
K + nucleus cytoplasm membrane
Potassium K + (Latin Kalium)
Sodium Na + (Latin Natrium) extra-cellular fluid

voltage dependent sodium channels
NERVE CELL
ONE WAY synapse neurotransmitters

ACTION POTENTIAL

THE CELL CONCEPT
KEYWORDS:
Cell, membrane, cytoplasm, nucleus, extracellular fluid ions, sodium, potassium, channels electrode, voltmeter, microelectrode, resting potential millivolt (1/1000 volt)
NERVE CELLS sodium channels, action potential axons, synapse, neurotransmitter, millisecond

SUBJECT
Half-silvered mirror
VIEWER
How an OPHTHALMOSCOPE works

Optic
Disc Fovea

RETINAL PROPERTY PERCEPTION
1 Image upside down >>>>> seen right way up
2 image is very small >>>>> world seen actual size
3 image on a curved surface >>>>> no curve seen
4 TWO retinas >>>>> only ONE world seen
5 blood-vessel tree >>>>> no tree seen!!!

RETINAL PROPERTY PERCEPTION
1 Image upside down >>>>> seen right way up
2 image is very small >>>>> world seen actual size
3 image on a curved surface >>>>> no curve seen
4 TWO retinas >>>>> only ONE world seen
5 blood-vessel tree >>>>> no tree seen!!!
6 BLIND SPOT (where the nerve comes in ) has no receptors >>>>> no hole seen!
7 only the central part of the no difference in retina is very sensitive >>>>> clarity between vision in different parts of the field

Filling in

Visual memory test: what letters are on the
‘4’ key?

So: visual input is poor visual memory is poor therefore vision is poor!
We are almost blind!!

Sometimes: we see what is not there do not see what is there
(Do we ever see what
IS there?! There might be more to this perception thing than meets the eye..)

Adaptation

.. than this one.
.. than this one.
This one appears brighter...
This one appears dimmer...
Under PHOTOPIC CONDITIONS but under SCOTOPIC CONDITIONS

Structure of eye and retina

lens
STRUCTURE OF THE EYE retina pupil
EXPANDED
VIEW cornea blind spot optic nerve retinal ganglion cell bipolar cell photoreceptor
LIGHT to the blind spot where this fibre will become part of the optic nerve inner layer middle layer outer layer
The eye and its optics 4 - 1

Rod cone

RECEPTIVE FIELD: the area in which energy will have an effect
VISUAL RECEPTIVE FIELD: the area in the outside world where light will have an effect

The Visual Receptive Field of a single photoreceptor.
Light outside this region will have no effect on this cell.
screen a single rod

The foveal pit

Different shape
Different distribution edge BLIND
SPOT
FOVEA
BAD starts off bad edge
Different sensitivity gets very good
GOOD
GOOD time in dark
RODS
CONES
Different pigments
BAD
BLUE RED edge BLIND
SPOT
FOVEA edge
BAD starts off better than rods
GOOD doesn't improve much time in dark
GOOD
RODS CONES
BAD
BLUE RED

lens
STRUCTURE OF THE EYE retina pupil
EXPANDED
VIEW cornea blind spot optic nerve retinal ganglion cell bipolar cell photoreceptor
LIGHT to the blind spot where this fibre will become part of the optic nerve inner layer middle layer outer layer
The eye and its optics 4 - 1

RETINAL GANGLION CELLS