The eye Flashcards
(20 cards)
What is the eye and what does it contain/do
The eye is a sense organ that contains receptor cells that are sensitive to light intensity and colour. they are located in the back of the eye called the retina. They all allow us to see
role of the cornea
Refracts light as it enters the eye
role of the iris
controls how much light enters the pupil by changing the size of it
role of the lens
further refracts light to focus it on the retina - changes direction of light rays
role of the retina
contains light receptors
role of the optic nerve
Carries impulses between the eye and the brain
role of the sclera
tough, white outer layer of the eye helping to protect it from injury
role of suspensory ligaments
Attaches lens to ciliary muscles
role of ciliary muscles
changes shape of the lens to allow contraction and relaxation
What is the pupil reflex
Amount of light that enters the eye. The size of the pupil changes in response to bright or dim light
What happens to the eye in Dim lighting
Pupil dilates, allowing more light in
Radial muscles contract and circular muscles relax
what happens in the eye in bright lighting
Pupil constricts, radial muscles relax and circular muscles contract
What is adaptation
features in the eye that help it function effectively like:
being able to change pupil size in different lighting
what is accommodation
A process where the lens changes shape to focus on near or distant objects
How does the eye focus on a DISTANT object
- Ciliary muscles relax, causing diameter of muscles to increase
- Pull on suspensory ligaments increase and they become taut
- the lens becomes flatter
- light rays are refracted less as they pass through the lens and focus a clear image onto the retina
How does the eye focus on NEAR objects
- Ciliary muscles contract, causing the diameter of the muscles to decrease
- This reduces pull on suspensory ligaments and they become slack
- lens becomes more convex
- light rays are refracted more as they pass through the lens and a clear image is produced on the retina
Two most common defects of the eye
- myopia: short sightedness
- hyperopia - long sightedness
why do people have myopia and how to treat it
Myopia is when the lens is too thick, and light rays refract and meet/focus before reaching the retina.
To fix this, a concave lens is placed in front of the eye, so light rays are less refracted and they focus on the retina
why do people have hyperopia and how is it treated
Hyperopia is when the lens is too thin, and light rays refract and meet/focus behind the retina, so a clear image isn’t focused.
To fix this, a convex lens is placed in front of the eye so light rays are refracted more and meet at the retina
Ways to treat eye defects
- hard and soft contacts: ideal for high movement activities like sport
- laser surgery: risk of unexpected damage, leading to worse vision or an infection
- lens replacement surgery: more invasive than laser eye surgery and carries a higher risk of damage to the retina
