10.2 Sight Flashcards
3 main parts of eye
Eyebrow, eyelid, eyelash
Eyebrow function
X sweat
Eyelid function
Close: dirt, strong light
Blink: moisten surface
Eyelash function
X small particles (dust)
80% of the eye is hidden in the _____
Socket
10 parts of eye
Focusing muscle Sclera
Cornea Retina
Iris Blind spot
Pupil Optic nerve
Lens
Jelly-like fluid
Focusing muscle function
Lens thickness
Cornea function
Light pass, focus light
Iris function
Pupil size
Pupil function
Regulate amt of light
Lens function
Light pass, focus light
Jelly like fluid function
Focus light
Maintain eyeball shape
Sclera function
Protect eyebal
Retina function
Light sensitive cells detect light, produce signals
Blind spot function
Optic nerve leaves
No cells
Optic nerve function
Signals brain
All 10 parts of eye and functions
Focusing muscle: lens thickness Sclera: protect eyeball
Cornea: light pass, focus light Retina: light sensitive cells detect light, signal
Iris: pupil size Blind spot: optic nerve leaves, no cells
Pupil: regulate amt of light Optic nerve: signals brain
Lens: light pass, focus light
Jelly-like fluid: eyeball shape, focus light
When and how does pupil size change to regulate amt of light
Bright: smaller, decrease light
Dim: larger, increase light
How are images formed in the eye
- Light enters
- Cornea, lens, jelly like fluid focus light onto retina
- Sharp inverted image on retina; light sensitive cells on retina stimulated by light, produce signals
- Signals sent to brain through optic nerve; interprets signals as upright image.
The lens is ____. It’s thickness can be changed by the _________ surrounding it, so that _______ from objects at different distances can be focused onto the _________.
Elastic, focusing muscles, light, retina
What does function of each part of the eye relate to
Its form
Lens is transparent -> light can pass through
Lens is elastic -> thickness can be changed
Looking at near objects
Focusing muscle contracts, thicker lens
（縮、厚片）
Looking at distant objects
Focusing muscle relaxes, thinner lens
（放鬆、薄片）
2 kinds of light sensitive cells on retina
Cone cells, rod cells
Cone cells
- bright light sensitive
- 3 types (rgb)
- detect colour
Rod cells
- dim light sensitive
- cant detect colour
Why difficult to distinguish colours in dim light
Only rod cells are stimulated and send signals to brain
They cant detect colour
Our eyes have ______. Cant see obj that are too _____, _____ or _____
Limitations, small, close, far
We can use ________ to extend our vision
Optical instruments
What optical instruments and what they can see
- Binoculars: birds
- Hand lens: bee
- Light microscope: plant cells
- Electron microscope: viruses
- Astronomical telescope: mars
What’s another limitation, where and why
Blind spot, located on retina
No light sensitive cells; when image is formed, no signals are sent to brain, cant see obj
Common eye defects
Short sight long sight
Astigmatism
Cataract
Colour blindness
Short sight
Reason, cause, correction
Image is formed in front of retina
Lens too thick / Eyeball too long / both （厚長）
Concave
Long sight
Reason, cause, correction
Image formed behind retina
Lens too thin / eyeball too short / both (薄短）
Convex
Astigmatism
Cause, reason , correction
Cornea / lens / both unevenly curved
Light can’t be focused on retina
Diff curvatures at diff points
Cataract
Reason, cause, correction
Light cant pass through cloudy lens -> blurred vision
Old age, eye injuries, prolonged sunlight exposure, heredity
Artificial lens through surgery
Colour-blindness
Reason, cause, correction
Defect in one or more cone cells, affect distinguish colours
Inherited
No correction
How to protect our eyes
- Rest, distant obj
- Sufficient, not strong light; read 30cm
- Monitor 50-70cm
- Goggles
- Regular eye checkups
- Hat, sunglasses
- X bend
- X moving vehicle
- X rub, infection
