Chapter 6 - The Eye and Vision Flashcards
What part of the brain processes information from the eyes?
The visual cortex
What part of the eye is the cornea?
The translucent part of the front of the eye which allows light to enter the eye.
How much focussing is the cornea responsible for?
70-80%
What is the liquid in front of the lense of the eye called?
The Aqueous Humour
What is the liquid behind the lense of the eye called?
The Vitreous humour
What is the role of the iris in the eye?
To contract and expand to regulate the amount of light entering the eye.
What is the pupil in the eye?
The hole/gap in the iris, where light enters the eye.
How does an objects distance affect the pupil size?
An object further away requires more light and so a larger pupil and vice versa.
What is the role of the lens in the eye?
It is the final focussing point, and focusses light onto the retina.
What is the role of the ciliary muscle in the eye and what is the result called?
It changes the shape of the lens by contracting.
This is called accomodation.
What is accomodation of the lens affected by?
Aging
Fatigue (tiredness)
What happens during accomodation for distant and close objects?
Distant:
Ciliary muscles relax, suspensory ligaments pull against lens, lens becomes flatter
Close:
Ciliary muscles contract, suspensory ligaments relax, lens becomes thicker and rounder.
What is the retina in the eye?
It is the light sensitive inner lining that contains photoreceptors (cones/rods)
What is the sclera in the eye?
The outer layer that makes the “white” of your eye.
What are cones and rods in the eye and what do they do?
Light sensitive cells/photoreceptors.
They convert light into electrical impulses to be sent to the brain.
What is the fovea in the eye?
The part of the retina that only contains cones and has a very high conventration of them (150000/mm).
It is the part where the most detail can be seen in day light.
What is the distribution of rods and cones on the retina?
At the fovea the concentration of cones is very high but as soon as you move away the concentration decreases rapidly.
Around the edge of the fovea is where the highest concentration of rods are and as you go further away the concentration slowly decreases.
There are no rods in the fovea.
What causes the blind spot in the eye?
The position where the optic nerve joins the eye causes there to be no photoreceptors at that spot.
What are the features of cones in the eye?
Colour sensitive
Work in bright light
Responsible for central vision (acuity and enables detail, colour and movement to be seen)
What are the features of rods in the eye?
See black and white
Sensitive in low light
Very sensitive to movement
Used for peripherals and night vision
Why is night vision affected by hypoxia?
Because the photoreceptors are the second part of the body most hungry for oxygen (brain being first)
What is vision through rods called?
Scotopic vision
What is vision through cones called?
Photopic vision
How long does it take rods and cones to adapt from dark to light conditions?
Around 10 seconds.