eye Flashcards
what is the role of the retina
contains light and colour sensitive receptor cells
what is the role of the sclera
though white protective layer so eye does not get damaged
what is the role of the optic nerve
The optic nerve is a bundle of sensory neurones at back of eye. It carries impulses from the eye to the brain
Describe the structure and function of the cornea.
The cornea is a transparent area at the front of the eyeball. It is convex and transparent. The cornea refracts light - bends it as it enters the eye.
Describe the structure and function of the iris.
The iris is pigmented - decides the colour of your eyes - so light cannot pass through.
Its muscles contract and relax to alter the size of its central hole or pupil which controls how much light enters the pupil.
Describe the structure and function of the ciliary muscles.
The ciliary muscles change the shape of the lens so that the image always comes to a sharp focus on the retina.
Describe the structure and function of the lens.
The lens is a ransparent, bi-convex, flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles.
The lens focuses light onto the retina.
Describe the function of the suspensory ligaments.
Attaches ciliary muscles to the lens
What is accomodation?
Accomodation is the process of changing the shape of the lens to focus on near or distant objects.
Explain what happens to the ciliary muscles, suspensory ligaments and the lens in order to focus on a near object.
In order to focus on a near object:
the ciliary muscles contract
the suspensory ligaments loosen
the lens becomes thicker and refracts light rays strongly.
Explain what happens to the ciliary muscles, suspensory ligaments and the lens in order to focus on a distant object.
In order to focus on a near object:
the ciliary muscles relax
the suspensory ligaments tighten
the lens becomes thinner and only slightly refracts light rays.
What is myopia?
Myopia is also known as short sightedness. People with myopia can see close objects with clear focus but distant objects look blurred.
This may be a result of a lens that is too curved or a long eyeball. The light is focused infront of the retina.
What is hyperopia?
Hyperopia is also known as long-sightedness. People with hyperopia can focus clearly on distant objects but close objects appear blurred.
This may be a result of a lens that is too flat and thin or a short eyeball. This means that the lens cannot refract the light rays stongly enough and light is focused behind the retina.
Describe how myopia can be treated.
Myopia can be treated by wearing glasses with a concave lens that spread out the light rays from distant objects before they reach the eye.
Describe how hyperopia can be treated.
Hyperopia can be treated by wearing glasses with a convex lens. This brings the light rays together before they reach the eye.
