The eye Flashcards
What is the function of the cornea and where is it located?
Front part of the tough outer coat, the sclera. It is convex and transparent.refracts light - bends it as it enters the eye
What is the function of the iris and where is it located?
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. It controls how much light enters the pupil and is in front of the lens.
What is the function of a lens and where is it located?
Transparent, bi-convex, flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles. The lens focuses light onto the retina and is situated in the front middle of the eye.
What is the retina and where is it located?
The lining of the back of eye containing two types of photoreceptor cells - rods - sensitive to dim light and black and white - and cones - sensitive to colour. A small area called the fovea in the middle of the retina has many more cones than rods. The retina contains the light receptors and is found at the back of the inner eye wall.
What is the optic nerve and where is it located?
Bundle of sensory neurones at back of eye.carries impulses from the eye to the brain
What is stereoscopic vision?
Because our eyes sit side by side, each eye captures a slightly different view. This is called stereoscopic vision. When signals from the two eyes reach the brain, they are superimposed and processed into a single picture with depth. As a result, we get a 3D picture and are able to judge distances well.
What is short sightedness?
Someone with short-sightedness can see near objects clearly, but cannot focus properly on distant objects. This is because the lens focuses the sharpest image in front of the retina, instead of on it.
What is long sightedness?
Someone with long-sightedness can see distant objects clearly, but cannot focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it.
What is colour blindness?
Colour blindness is an inherited condition. The retina contains cells that are sensitive to red, green or blue light. People with colour blindness have a lack of receptors, or defects in them. People with red-green colour blindness, for example, have difficulty distinguishing shades of red and green.
