The Eye Flashcards
What type of organ is the eye
A sense organ
What is the sclera
A tough supporting wall of the eye
What is the cornea and what does it do
The transparent outer layer found at the front of the eye
It refracts light into the eye
What does the iris do and where is it
It’s inside the pupil and it contains muscles that allow it to control the diameter of the pupil and how much light enters the eye
What’s the lens’ job
It’s focuses the light into the retina
What does the retina contain
Receptor cells sensitive to light intensity and colour
What is the shape of the lens controlled by
The ciliary muscles and suspensory ligaments
What is the optic nerve
It carries impulses from the receptors in the retina to the brain
Why is there the iris reflex
It protects you from very bright light which can damage the retina
How is the iris reflex triggered
When light receptors in the eye defect very bright light
What does the iris reflex do when bright light is detected
It makes the pupils smaller and the circular muscles in the iris contract and the radial muscles relax
This reduces the amount of light that can enter your eye
What are the 2 muscles in the iris
Circular muscles
Radial muscles
What happens to the muscles in the iris in dim light
The radial muscles contract and the circular muscles relax making the pupil wider so it can take in more light
What is accommodation
When the eye focuses light on the retina by changing the shape of the lens
What happens to the ciliary muscles when looking at near objects
They contract which slackens the suspensory ligaments
What happens to lens when looking at near objects and what does this do
The lens becomes fat which increases the amount it refracts light
What happens to the ciliary muscles when looking at distant objects and what does this do to the lens
They relax which allows the suspensory ligaments to pull tight which makes the lens go thin
What happens to the amount of refraction when the lens gets thinner
The amount it refracts gets smaller
What does it mean if you are long sited
And what is the medical term for longsightedness
You are unable to focus on near objects
Hyperopia
How are people long sited
The lens will be the wrong shape and won’t refract enough light or the eyeball is too short
The images of near objects are brought into focus behind the retina
What lenses are used to correct long sited people
Glasses which have a convex lens
The lens curves outwards to correct it
The lens refracts the light ray so they focus on the retina
What does it mean if you are short sited
And what is it’s medical term
You are unable to focus on distant objects
Myopia
What does the lens do if you are short sited
It’s the wrong shape and refracts light too much
The images of near objects are brought into focus in front of the retina
What lens’ are used to correct short sitedness
Concave lens the lens curves inwards
What are several treatments for vision defects apart from glasses
Contact lenses
Laser eye surgery
Replacement lens surgery
What are the advantages of contact lenses
Lightweight and almost invisible
More convenient for sport activities
Disadvantages of soft lenses
Carry a higher risk of eye infections than hard lenses
How does laser eye surgery treat the eye
It vaporises the tissue and changes the shape of the cornea
What happens in replacement lens surgery
Natural lens of the eye is removed and an artificial plastic lens is inserted
Does laser eye surgery or replacement lens surgery carry higher risks
Replacement lens surgery
