made up of light sensitive cells which create an image
Lens
Jelly like material brigs light through to focus on retina
Iris
ring of coloured muscle that controls the size of the pupil
Pupil
Hole which lets different amounts of light into the eye
Ciliary muscles
control the shape of the lens
Contract when an object is close, lens gets fatter
Relax when object is far, lens is thinner
Opticnerve
Carries electrical signals o the brain
Close objects
CM contract , SL slacken, lens fatter , strong refraction
distant objects
CM relax, SL stretch, lens thinner, weaker refraction
Cornea
thick transparent layer which helpsfocus the light and protects it
Sclera
Tough supporting wall of the eye
what is the retina made up of
Receptor cells -
rod cells- more sensitive to light, only black and white
Cone cells- sensitive to Colour so we can see colour
fovea
main spot on the retina which light focuses on to help us see clearly, has only cone cells
Myopia
short sightedness
light focusesed in front of the retina
Cause- eyeball is too long , lens is too curved
Solution - concave lens which spreads out the light so it focuses on retina
Hyperopia
longsightedness
Light is focused behind the retina
Causes - eyeball is too short and lens isn’t curved enough
Solution - convex lens which brings the light tgr so it focuses on retina
accomodation
changing the shape of the lens to allow light to focus on the retina
Bright light
Circular muscles contract, radial muscles relax, pupil gets smaller , less light goes through
Dim light
Circular muscles relax, radial muscles contract, pupil gets bigger, more light is let through
Treatments for vision defects
laser eye surgery, using a laser to change the shape of the cornea to refract light better, for short sighted people the cornea is shaved slimmer reducing the refraction, for long sighted ppl the cornea is made bigger to increase refraction
Contact lenses- thin convenient lens that helps refract light, softlens - comfortable , hard lens- risk of eye infections
lens replacement- faulty lens is removed and replaced w an artificial one but high risk bcs Retina cld get damaged and patient can go blind
Blind spot
Small area in the retina where no light is detected bcs there aren’t any rod or cone cells