eye COPY Flashcards
name the structures that the eye contains
retina, lens, cornea, pupil/iris, ciliary muscle, suspensory ligaments
what is the function of the retina
Contains the light receptors, which trigger electrical impulses to be sent to the brain when light is detected.
what is the function of the lens
Refracts light to focus it onto the retina. The amount of refraction can be adjusted by altering the thickness and curvature of the lens.
what is the function of the cornea
Refracts light as it enters the eye (by a fixed amount).
what is the function of the pupil/iris
The iris relax or contract to adjust the size of the pupil. Controls how much light enters the pupil.
what is the function of the ciliary muscle
Adjust the shape of the lens to make it more or less curved, so as to increase or decrease the refraction of light. These changes in the shape of the lens allow light to be focused at varying distances.
what is the function of the suspensory ligaments
Slacken or stretch as the ciliary muscles contract or relax, to adjust the thickness and curvature of the lens.
what is the retina
The lining of the back of eye containing two types of light receptor cells. Rods are sensitive to dim light and black and white. Cones are sensitive to colour.
what is the lens (of the eye)
Transparent, bi-convex, flexible disc behind the iris. It is attached to the ciliary muscles by the suspensory ligaments.
what is the cornea
Tough, transparent covering over the front part of the eye. Convex in shape.
what is the pupil
Hole in the middle of the iris.
what is the iris
Coloured part of the eye that contains muscles.
what are the ciliary muscles
Muscles connected to the lens by suspensory ligaments.
what are the suspensory ligaments
Connect the ciliary muscles to the lens and hold the lens in place.
what is the usual near and far point of the human eye
usually the near point of the human eye is approximately 25cm and the far point is infinity. the eye can focus on objects between the near point and the far point. the distance between these points is the range of vision.
what is long sight caused by
it is caused by the eyeball being too short, or the eye lens being unable to focus.
what is short sight caused by
it is caused by the eyeball being too long, or the eye lens being unable to focus
how does long sight present itself (and what can be done)
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. This defect is often age-related, and due to a loss of elasticity in the lens. It is corrected by putting a convex lens in front of the eye.
how does short sight present itself (and what can be done)
Someone with short-sightedness can see near objects clearly, but cannot focus properly on distant objects. This is caused by the eyeball being elongated, so that the distance between the lens and the retina is too great. It can be corrected by placing a concave lens in front of the eye.
describe how the shape of the lens is changed for distant objects
the ciliary muscles relax, the suspensory ligaments stretch and the shape of the lens is thin - less convex.
describe how the shape of the lens is changed for nearby objects
the ciliary muscles contract, the suspensory ligaments slacken and the shape of the lens is fat - more convex.
what are lasers
lasers are a concentrated source of light
what can lasers be used for
lasers can be used for cutting, cauterising and burning. lasers can be used in eye surgery, to correct visual defects.
what is similar between the structure of the eye and the camera
in the eye the image is brought to focus on the retina by changing the shape of the lens, in a camera the image is brought to focus on the film by varying the distance between the film and the lens
what part of the eye is the equivalent of the film in a camera
the film in a camera is the equivalent of the retina in the eye
