Bio - The Eye Flashcards
What is the function of the sclera
It’s the tough supporting wall of the eye
What is the function of the cornea
It’s the transparent outer layer at the front of the eye and refracts light into it
What is the function of the iris
Contains muscles which allow it to control the diameter of the pupil
What is the function of the lense
To focus light onto the retina
What is the function of the ciliary muscles and suspensory ligaments
To control the shape of the lense
What’s the function of the optic nerve
To carry impulses from the receptors in the retina to the brain
Why must the pupil become smaller in bright light?
To protect the retina
What muscles when contracted make the pupil smaller
The circular muscles
What muscles when contacted widen the eye
Radial muscles
When looking at a near object…
Ciliary muscles contract slackening the suspensory ligaments and making the lens become fat increasing the amount it refracts light
When looking at a distant object…
Ciliary muscles relax allowing suspensory ligaments to pull tight and makes the lens go thin so it refracts light a smaller amount
How does long sightedness happen?
- The lens is the wrong shape and doesn’t refract the light enough
- The eyeball is too short
Where does the image form in long sightedness
Behind the retina
Where does the image form in short sightedness
In front of the retina
How does short sightedness happen
- The lens is the wrong shape and refracts light too much
2. The eyeball is too long
What’s the medical term for long sightedness
Hyperopia
What’s the medical term for short sightedness
Myopia
What sort of lens can correct long sightedness
A convex lens (bulgy) looks like ()
What sort of lens can correct short sightedness
A concave lens (bendy) looks like )(
What are three alternatives to glasses
- Contact lenses
- Laser eye surgery
- Replacement lens surgery
One advantage to contact lenses
They’re lightweight and almost invisible
One disadvantage to contact lenses
Eye infections
How does laser eye surgery work
Vaporises tissue from the cornea
Disadvantage to laser eye surgery
There’s always a risk of complications
Advantages to laser eye surgery
It’s permanent
What does slimming down the cornea do
Makes it less powerful and improve vision for short sighted people
What would changing the shape of the cornea do
Make it more powerful which improves vision for long sighted people
How is replacement lens surgery done
The faulty lens is replaced by an artificial one made of plastic
What’s a disadvantage to replacement lens surgery
Has higher risks than laser eye surgery and could damage the retina
