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The Eye and Problems with it (Structures of Eye (Pupil - The hole in the…
The Eye and Problems with it
Structures of Eye
Pupil
- The hole in the middle of the eye
Lens
- Focuses the light onto the retina
Iris
- Contains muscles that allow it to control there diamond of the pupil (hole in the middle) and therefore how much light enters they eye
Retina
- Contains receptor cells sensitive to light intensity and colour
Cornea
- Transparent outer layer found at front of eye. It refracts light into the eye
Ciliary Muscles
- Controls shape of lens
Sclera
- Tough, supporting wall of the eye
Suspensory Ligaments
- Controls shape of lens
Optic Nerve
- Carries impulses from the receptors onto the truna to the brain
Focusing the Light
Looking at distance objects
This makes the lens go thin (less curved)
So it refracts light by a smaller amount
The ciliary muscles relax which allows the suspensory ligaments to pull tight
Looking at near objects
The ciliary muscles contract, which slakens the suspensory ligaments
The lens becomes fat (more curved)
This increases the amount by which it refracts light
Iris Reflex
When light receptors in the eye detect very bright light, a reflex is triggered that makes the pupil smaller. The circular muscles in the iris contract and the radial muscles relax. This reduced the amount of light that can enter they eye
The opposite prrocess happens in dim light. This time the radial muscles contract and the circular muscles relax, which makes the pupil wider
Very bright light can damage tetina so you have a reflex to protect it
Myopia
Light is focused in front of retina so images that actually land on retina seem out of focus and blurry
May be result of lens being too curved or they eyeball being long
If you have this you can see close objects in clear focus but distant objects look blurred
Treated by wearing concave lens glasses
Hyperopia
This may be the result of the lens being too flat and thin or a short eyeball
As a result the lens cannot refract the rays of light strong enough meaning the light is focused behind the retina
If you have this you can see distant objects in clear focus but close objects look blurred
Can be trated by wearing glasses with convex lenses