Chapter 6 extra Flashcards
What is vision?
Vision is how we see
What is weird about how we see?
Vision uses our brains much more than our eye balls
Where does light energy enter the eye?
Light energy enters the eye via the cornea
Where does light pass through?
Light passes through the pupil
What can the pupil do?
The pupil can expand and contract
Why does the pupil expand and contract?
The pupil expands and contracts to adjust the amount of light entering the eye
What helps focus the image?
the lens helps to focus the image
Where does light finally hit?
The light finally hits the retina at the back of the eye.
What does the retina have?
The retina has two types of cells: Cones and Rods
What are cone cells?
Cone cells are heavily involved in colour vision.
Where are cones found?
Cones are found in the area called the fovea, which is the center of the retina
Where is the fovea?
The fovea is in the center of the retina
When the viewer is looking directly at something, where does the image land on the back of the eye?
The image lands on the fovea when someone is looking at something directly
What are rods for?
Rods are important for black and white viewing.
Where are rods found?
Rods are mostly at the edge of the retina
Where does information from the rods and cones go?
The rods and cones send information through the optic nerves
What is the optic chiasm?
The optic chiasm is where the optic nerves cross before the enter the brain.
Why do the optic nerves cross?
The optic nerves cross so that the brain gets information from both eyes
Where does the information travel after the optic chiasm?
Lateral Geniculate nucleus (LGN) to the primary visual cortext (V1) and then to the occipital lobe
What happens to the image when it enters the eye?
Because it is a reflection it is flipped upside down and reversed, so the brain has to put it the right way up.
What is the first thing the brain does?
The first thing the brain does is to flip the image upright and from right to left
What does the occipital lobe do?
The occipital lobe processes the correct information
What is perception?
Perception is when you become aware of the image that has entered your brain.
What is myopia?
Myopia is near-sightedness.
What is near-sightedness?
you are able to focus on close objects but distant objects are out of focus… ie you need glasses to drive or see the board but not to read
How does myopia happen?
When light enters the eye and it converges (meets) at a point in front of the retina instead of on the retina
What shape is the eye if you have myopia?
The eye is too long front to back – axial myopia
What shape is the refractive tissue (the cornea and lens) if you have myopia?
If you have myopia you cornea and lens are too high, which causes the image to focus in front of the retina, which makes distant objects blurry
Who is an optometrist?
An optometrist is a person who measures your eyesight and prescribes glasses.
What are corrective lenses?
Corrective lenses are lenses that go into glasses to fix bad vision
How is myopia corrected?
Myopia is corrected with concave glasses lenses
How do concave lenses help?
Concave lenses diverge (spread out) the light and push the focal point further back onto the retina
What is hyperopia?
hyperopia is far-sightedness
What is far-sightedness
far sightedness or hyperopia is when near objects are out of focus, so you can see well to drive or see the board but you can’t see the words to read a book.
What happens to the light in hyperopia or far-sightedness?
In far-sightedness the light converges (meets) at a focal point behind the retina, so objects are out of focus
What is wrong with the eye that you get hyperopia?
Hyperopia or far-sightedness is caused by the eye being too short or the power of the refractive tissue being too low
If you have extreme hyperopia what happens?
IN extreme cases of hyperopia, everything is blurry
How is hyperopia fixed?
Hyperopia or far-sightedness is corrected with a refractive lens
What is the lens shape that fixes far-sightedness?
A convex lens is for far-sightedness
How does a convex lens change the light rays?
A convex lens changes the light rays by converging them (bringing them together) and pulls it further forward onto the retina.
What is presbyopia?
Presbyopia is the deterioration of the eye as you age.
Is presbyopia an illness?
No presbyopia is a natural part of aging.
What happens in presbyopia?
it becomes increasingly difficult to see images up close, in dim light and if there is sharp detail
How does this lack of focus happen?
The crystalline lens just behind the surface of your eye starts to harden and is less flexible
What happens when the lens isn’t flexible?
When the lens loses its flexibility, you cannot focus your eyes as well
How can presbyopia be fixed?
Convex lenses fix presbyopia
What is the purpose of contact lenses?
Contact lenses replace glasses and correct vision.
What is laser eye surgery?
Laser eye surgery reshapes the cornea of the eye (the clear window that light passes through)
What cuts the cornea?
Instead of scalpel (knife) the surgeon uses a laser
What is a laser?
A laser is a device that emits (gives off) amplified light (light that has more energy)
How is the laser beam used?
The laser vaporizes (turns from liquid to gas) the soft tissue of the eye’s cornea
