Eye Flashcards
The eye contains light sensitive ___
Photoreceptors
Rods
Active when light - poor intensity
Gives rise to black and white vision
Cones
Sensitive when light is high intensity
Permit color vision
How is the eye protected
- eyeball is situated in a bony socket : protects everywhere except front (protected by lashes and lids). Sockets padded with fatty deposits
- eyelids lined with conjunctiva ( thin sensitive membrane). When stimulated, causes blinking and secretion of tears
- glands of Meiboom: inside eyelids, secret fluid that lubricates movem. Of eye, traps foreign particles.
- lachrymose glands release lachrymose fluid (tears): wash dust from eye, destroy germs, prevents desiccation, lubricates movem.
What is the conjunctiva
Thin sensitive membrane lining eyelid
Causes blinking and tears when stimulated
What does the lachrymal gland release and what does it do
Lachrymal fluid (tears) Washes dust from eye, destroys germs (contains lysozyme) prevents desiccation, lubricates movem.
Which two fluids protect the eye and lubricate movem.
Glands of Meiboom secret fluid
Lachrymal glands
(Functioning of the eye)
What is binocular vision
Ability to focus on one object using both eyes. Each eye has a separate image and the brain puts the two images together, allows us to have 3D view
(Functioning of eye)
Describe pupillary mechanism
High intensity light can damage the eye, therefore it’s important the amount of light that enters is regulated. This is controlled by the iris which has circular and radial muscles which are antagonistic
(Functioning of the eye)
Accommodation (definition)
The adjustment of the curvature of the lens for vision at different distances
Describe accommodation
At rest: eyes adapted for viewin objects within a range of 6m
Anything closer/farther than this requires adjustment of the curvature of the lens.
The lens is stretchy and elastic, can bulge/flatten when focusing on objects at different distances.
Change of curvature changes refraction of light so the Rays fall on the retina.
Ciliary muscles and suspenders ligaments (hold the lens in position) are responsible for the curvature of lens
(Accommodation)
What are the ciliary muscles and suspends pry ligaments responsible for
- holding the lens in position
- changing the curvature of the lens
(Accommodation)
Why and how does the lens change when focusing on different distances
The lens is stretchy and elastic and can bulge/flatten
Compare: Near vision. Vs distant vision for; - ciliary muscles - suspensory ligaments - lens
Near vision
- muscle contracted
- slack and distance small
- bulges, thick
Distant vision
- relaxed
- tight, distant, tense
- flat, thin
Name the four eye disorders
1) myopia (short-sightedness)
2) longsighted/ hyperopia/ presbyopia
3) astigmatism
4) cataracts
Ability to focus on near objects, distant objects are blurred. Eyeball is too long, image falls in front of retina instead of on.
Myopia
Can see distant objects, near is blurred. Eyeball too short, image falls behind retina instead of on.
Long sightedness
Caused by an irregularly shaped cornea/ lens, causing blurred vision.
Astigmatism
Cloudy region that appears on the lens due to accumulation of certain proteins in these regions. Lens no longer completely transparent, therefore harder to see.
Cataracts
Can be treated with glasses/ contact lenses with concave lenses to diverge incoming light rays
Myopia
Can be treated with glasses/ contact lenses specifically shaped for the particular individual.
Astigmatism
Can be treated with glasses/ contact lenses with convex lenses to bend the light rays further together
Long sightedness/ hyperopia
Can be treated with surgery. Clouded lens removed and replaced with a plastic intraocular lens
Cataracts
