Unit Three: The Eye Flashcards
What is the cornea?
A transparent ‘window’ with a convex shape and a high refractive index.
The cornea does most of the eye’s focusing
What is the iris?
What is the pupil?
The coloured part of the eye.
It’s made up of muscles that control the size of the pupil - the hole in the middle of the iris.
This controls the the intensity of light entering the eye.
What is the lens?
It changes shape to to focus light from objects at varying distances.
It’s connected to the ciliary muscles by the suspensory ligaments and when the ciliary muscles contract, tension is released and the lens takes on a fat, more spherical shape.
When they relax the suspensory ligaments pull the lens into a thinner, flatter shape.
How are images formed (in the eye)?
They are formed on the retina, which is covered in light-sensitive cells.
These cells detect light and send signals to the brain to be interpreted.
How is short sight corrected?
With diverging lenses
How is long sight corrected?
With converging lenses
What is short sight caused by?
The eyeball being too long, or by the cornea and lens system being too powerful
What is long sight caused by?
The cornea and lens being too weak, or the eyeball is too short
How does laser eye surgery work?
The laser is used to vaporise some of the cornea to change its shape, which changes focusing ability
What do optical fibres do?
Carry visible light over long distances
What is an endoscope?
How is it used?
Give an advantage:
- A think tube containing optical fibre that allows surgeons to examine inside the body
- They consist of two bundles of optical fibres (one to carry light and and one to carry an image back to be viewed)
- Surgeons can perform operations by only cutting tiny holes (keyhole surgery)
