topic 2 the eye Flashcards
outline the structure and function of the retina
● Light sensitive layer composed of rod and cone cells
● Converts light energy into neural signals which are sent to the brain via the optic nerve
What are cone cells?
Cells found in the retina that are sensitive to high light intensity (bright light) and can detect different colours.
describe how dim light affects the size of the pupil
● Light receptors detect dim light ● Circular muscles relax ● Radial muscles contract ● Pupil dilates ● More light enters the pupil
What is accommodation?
the process by which the eye’s lens changes shape to focus near or far objects on the retina
describe how the eye focuses on near objects
● Near object ● Ciliary muscles contract ● Suspensory ligaments slacken ● Lens becomes more convex (more rounded) ● Light is refracted more ● Light rays focused onto the retina
How is short-sightedness treated?
● Using a concave lens (causes light rays to diverge) in glasses or contact lenses
● Replacement lenses
● Laser eye surgery
How are cataracts treated?
The clouded lens is exchanged for a synthetic lens during surgery.
identify the structures of the eye labelled in the diagram below
A = cornea B = iris C = ciliary muscle D = lens E = suspensory ligamets F = retina G = optic nerve
outline the structure and the function of the cornea
transparent outer covering of the eye refracts light entering the eye
outline the structure and function of the iris
● Pigmented ring of circular muscles and radial muscles
● Controls the size of the pupil to alter how much light enters the eye
What is the pupil?
The hole in the iris center where light rays enter
outline the structure and the function of the lens
● Transparent, bi-convex structure
● Suspensory ligaments attach the lens to a ring of ciliary muscle
● Refracts light, focusing it onto the retina
what is the function of the ciliary muscles and suspensory ligaments
To change the shape of the lens to allow light to focus on the retina
What are rod cells?
Cells in the retina that are sensitive to low light intensity (dim light)
what is the function of the optic nerve?
It transmits nerve impulses to the brain from the retina.
describe how bright light affects the size of the pupil
● Light receptors detect bright light ● Circular muscles contract ● Radial muscles relax ● Pupil contracts ● Less light enters the pupil
Why is the iris reflex important?
It prevents bright light from damaging the retina.
Describe how the eye focuses on distant objects
● Distant object ● Ciliary muscles relax ● Suspensory ligaments tighten ● Lens becomes less convex (less rounded) ● Light is refracted less ● Light rays focused onto the retina
What is long sightedness?
Can’t focus on near objects
what are the causes of long sightedness
● Eyeball is too short
● Lens is less elastic (usually age-related)
● ∴ light rays are not focussed onto the retina, instead converging behind the retina
How is long-sightedness treated?
● Using a convex lens (causes light rays to converge) in glasses or contact lenses
● Replacement lenses
● Laser eye surgery
What is short sightedness?
● Can focus on near objects clearly
● Cannot focus on distant objects
what are the causes of short-sightedness?
● Eyeball is too long
● Lens is too thick and too rounded
● ∴ light rays are not focussed onto the retina,
instead converging in front of the retina
What are cataracts?
clouding of the lens
What is colour blindness?
● A deficiency of the eye that makes it difficult to distinguish between colours
● e.g. individuals with red-green colour blindness have difficulty differentiating between red and green
what is the cause of colour-blindness?
Damage to cone cells in the retina
