SB2 The Eye Flashcards
What are the parts of the eye?
- cornea
- iris
- pupil
- lens
- retina
- optic nerve
What is the function of the cornea?
Transparent lens that refracts light as it enters the eye
What is the function of the iris?
Controls how much light enters the eye
What is the function of the lens?
Transparent disc that can change shape to focus light onto the retina
What is the function of the retina?
Contains light receptor cells
What is the function of the optic nerve?
Sensory neurone that carries impulses between the brain and the eye
What is the function of the pupil?
Hole that allows light into the eye
What is the function of the ciliary muscles?
A ring of muscle that contracts and relaxes to change the shape of the lens
What is the aqueous humour and where is it located?
The watery liquid between the cornea and the lens
What is the vitreous humour and where is it located?
Jelly-like substance filling the eyeball (behind the lens)
What are the two types of light receptors within the retina and what do they do?
- Cones: can detect colour
- rods: can detect light
How does the lens move?
Through the contraction and relaxation of the ciliary muscles
What happens if the lens wants to focus on a nearby object?
- ciliary muscles contract
- causing the lens to become fatter
- light is refracted more
What happens if you want to focus on a far-away object?
- ciliary muscles relax
- causing the lens to become thinner
- light is refracted less
What is the pupil reflex action and why is it carried out?
Reflex action carried out to protect the retina from damage
What happens to the pupil in dim light?
It dilates
What happens to the pupil in bright light?
It constricts
What is the effect of short-sightedness?
Distant objects blurry but closer objects clear
What causes short-sightedness?
- lens more curved than normal
- eyeball too long
What happens in short-sightedness?
- light is refracted too much
- causing the focal point to fall in front of the retina rather than on the retina
How is short-sightedness treated?
- using glasses with a concave lens
What are the effects of long-sightedness?
Close objects appear blurry but far away objects look fine
What are the causes of long-sightedness?
- lens less curved than normal
- eyeball too short
What happens in long sightedness?
- light isn’t refracted enough
- focal point falls behind the retina
How can long sightedness be treated?
Using convex lenses
What is the impact of colour-blindness?
Not all colours are seen
What is the cause of colourblindness?
Cones don’t work properly
What is cataract?
A condition that causes the build up of a lot of protein, clouding the lens
What is the effect of having cataract?
- light is dispersed throughout the lens
- or absorbed by the lens
- rather than focussing the light on one sharp point
How is cataract treated?
Replace the real lens with an artificial one
