Vision Flashcards
Cornea
is the transparent portion at the center front part if the eye that allows light through
Sclera
the firm white tissue that covers all of the eye. It helps maintain the shape of the eye and protects the inner parts
Pupil
The dark opening in the middle of your eye, surrounded by the iris. It allows light to enter your eye (black hole)
Iris
a group of muscles that controls how much light enters the eye by adjusting the opening or pupil. The iris contains pigments that determine your eye colour.
Lens
Part of the eye which changes shape, getting thicker or thinner
- It can adjust how much light is let in, focusing it as it beams it on the retina
- This is how you can create clear images of objects even if they’re at different distances
Ciliary Muscles
a group of muscles and ligaments that attach to the lens. These muscles change the shape of the lens as they relax and contract
Retina
is the inside lining of the back of the eye that changes light waves into electrical signals. (yellow)
Aqueous Humor
The area between the cornea and the lens is filled with a transparent liquid material called the aqueous humour
Vitreous Humor
The area between the lens and the retina contains a clear gel-like substance called the vitreous humor.
conjunctiva
covers the inside of the eyelids, the cornea, and the front portion of the sclera. It helps lubricate the eye
Optic nerve
The optic nerve transmits visual information from the retina to the brain along nerve cells
What are the four surfaces that bend light as it enters the eye?
Cornea, aqueous humour, lens and vitreous humour.
rods
rods see in black and white and in shades of grey. And tells us the forms or shape something has. They are super sensitive, allowing us to see when its very dark
cones
sense color and they need more light than rods work well. The retina has three types of cones. Each cone type is sensitive to one of three different colour, red bleu, green
Why can the eye focus objects at different distances?
The eye can focus objects at different distances because the ciliary muscles push and pull to make the lens change shape
Seeing objects that are far?
When you look at an object that is far away, the ciliary muscles relax and the lens has a flattened shape
Object that is close by
When you look at an object that is close by, the ciliary muscle are contracted and the lens is thickened
How many rods
120 million
how many cones
7 million cones
The Snellen Chart
A Snellen eye chart is used to determine how “normal” your vision is. It sets a standard for what most people should be able to see when they stand 20 feet away from the chart.
Farsightedness aka hyperopia
is a condition of the eye in which light is focused behind, instead of on, the retina. This results in close objects appearing blurry, while far objects appear normal.
Myopia aka nearsightedness
means that light is focussed in front of the retina. Close objects look clear but distant objects appear blurred.
The first known eyeglasse
made in the 13th century out of quartz set into bone, metal, or leather.
Who invented the first bifocals? Why?
Benjamin Franklin has two pairs of glasses, one for near and one for far. He got tired of changing them so he cut the lenses in half and repositioned them so that he could see both near and far using the same glasses, the first bifocals
Lasik
Some people want a more permanent solution to their vision problem. LASIK is a surgery that reshapes the cornea
How does lasik work
-The surgeon uses a sharp scalpel to cut a flap of the top layer of the cornea, then directs the laser into the middle layer. As the layer pulses onto this surface of the cornea and vaporizes a microscopic portion of the cornea. By controlling the number and location of the pulses, the surgeon controls how much of the cornea is removed
-If you’re nearsighted, the cornea need flattening
-If you’re farsighted, the cornea needs a steeper angle
Once the aviation is complete, the corneal flap is replaced so it can heal
What is your blind spot? Why do you not normally notice it?
The spot where your optic nerve connects to your retina is called the optic disc. There are no photoreceptors cells on this disc, so when an image hits that part of your retina, you can’t see it
This is your blind spot. You don’t notice this blind spot in everyday life, because your two eyes work tgt to cover it up
Cataracts
Cataracts are cloudy areas that form on the lens of your eye. Your lens is a clear, flexible structure made mostly of proteins. As you get older, the proteins in your lens break down, forming cloudy patches that affect your vision.
What happens during cataract surgery? How many people will need to get cataract surgery in their lifetime?
Cataract surgery removes your clouds lens and replaced it with a clear artificial lens
By age 65 more than 90 percent of people will develop cataracts and will need surgery
Glaucoma
Glaucoma is caused by damage to the optic nerve, which leads to visual field loss
What happens in your eye when you have glaucoma
Your eye constantly makes aqueous humor. As new aqueous flows into your eye, the same amount should drain out. The fluid drains out through an area called the drainage angle. But if the drainage angle is not working properly, fluid builds up, pressure inside the eye rises, damaging the optic nerve
As optic nerve diners die, you will develop blind spots in your vision. You may not notice these blind spots until most of your optic nerve fibres have died. If all the fibers die, you will become blind
Retinal Detachment
Retinal detachment describes an emergency situation in which a thin layer of tissue (the retina) at the back of the eye pulls away from its normal position.
Retinal detachment separates the retinal cells from the layer of blood vessels that provides oxygen and nourishment to the eye. The longer retinal detachment goes untreated, the greater your risk of permanent vision loss in the affected eye.
Macular Degeneration
It happens when a part of the retina called the macula is damaged. You lose your central vision. You cannot see fine details, whether you are looking at something close or far. But your peripheral vision will still be normal (very common)
