the eye Flashcards
how many layers in the eye and what r they called
-3 , fibrous, vascular and inner layers
what does the vascular layer consist of - 1
the iris, the coloured part of the eye which helps regulate amount of light entering
what does the inner layer consist of
- the retina, optic nerve and rods/cones
what is the pupil
opening at centre of eye which changes size to control amount of light entering the eye
what is the iris
iris is the coloured part of the eye. colour depends on amount of melanin. it controls the size of the pupil in ressponse to the brightness of light
inner layer
what is the retina
innermost layer of the eye which contains photoreceptors such as rods and cones it also contains nerve cells
- It converts the light rays into electrical signals and send them to the brain through the optic nerve
what is the fovea
No rods but many cone photoreceptors surrounding it.
* Fovea represents the area in our retina which has the highest acuity vision – centre of gaze
what r photoreceptors
rods and cones r photoreceptor cells which detect and respond to light in retina.
what is the purpose of rods and cones
rods : peripheral (eveyrthing that isnt central vision) vision and detection of movement & night vision
cones: colour & day vision - central vision management
inner layer
what is the optic nerve
- Connects the eye to the brain .
- Carries nerve impulses to the visual cortex of the brain.
what is refraction
Change in direction of light as a result of it travelling at different speeds in mediums of different densities, approaching the medium at an ANGLE .
is concave lens for myopia or hyperopia
myopia - thin centre, thick edges
is convex lens used for myopia or hyperopia
hyperopia, thicker in middle, thinner edges
what are the visual disorders
- myopia, hyperopia
what is myopia
nearsighted eye, the eyeball too long and faraway objects are blurry
what is hyperopia
near object is blurry eyeball is too short
what are the technologies used to correct eye sight
- spectacles
- refractive laser eye surgery (LASIK)
what are spectacles
glasses. two types. spectacles with diverging, concave lens which aims to reduce refactive power of lens
spectacles with converging convex lens, aims to add refractive power to eye
what is LASIK
This aims to change the curvature of the cornea to alter its refractive power. It involves :
cutting and lifting a flap of the cornea , leaving it partly intact.
Introducing laser to the middle layers of the cornea beneath the lifted flap.
Changing the shape of the cornea with the laser.
Myopia = flatten cornea
Hyperopia = steepen cornea
