P3.1a (The Eye) Flashcards
What is the function of the Cornea?
Refracts light as it enters the eye (by a fixed amount).
What is the function of the Iris?
Controls how much light enters the pupil.
What is the function of the Pupil?
Allows light to pass through as it enters the eye.
What is the function of the Ciliary muscles?
Adjust the shape of the lens to make it more or less curved, so as to increase or decrease the refraction of light.
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 function of the Retina?
Contains the light receptors, which trigger electrical impulses to be sent to the brain when light is detected.
What is ‘accommodation’?
The eye can alter the shape and curvature of the lens to adjust the degree of refraction.
How is accommodation achieved?
Accommodation is achieved by the contraction or relaxation of the ciliary muscles, which slacken or stretch the suspensory ligaments.
What is the ‘near point’?
The nearest point to the eye at which an object remains in focus.
What is the distance between the near point and the far point called?
Range of vision
Match up the following camera parts with structures in the eye: Lens, focusing screw, aperture, photosensitive surface.
lens = lens
focusing screw = ciliary muscle
aperture = iris
photosensitive surface = retina
What is a key difference between a camera structure and an eye structure?
A camera does not focus light onto the photosensitive surface by adjusting the shape of the lens. Instead, the focusing screws move the lens forwards or backwards in order to focus the image onto the photosensitive surface.
How is short-sightedness caused?
The eyeball being elongated - so that the distance between the lens and the retina is too great.
The lens being too thick and curved - so that light is focused in front of the retina.
How can short-sightedness be corrected?
By placing a diverging lens in front of the eye.
How is long-sightedness caused?
The eyeball being too short - so the distance between the lens and retina is too small.
A loss of elasticity in the lens - meaning it cannot become fat enough to focus (which is often age-related).
