Eyes and Lenses Flashcards
What does the iris do?
It controls the amount of light entering the eye and relaxes in bright light to reduce excess light from damaging the eye.
What is the pupil?
The hole in the centre of the iris
What is the retina?
The screen at the back of the eye
What are the rods?
The cells that behave as brightness indicators
What are the cones?
The cells that sense red, green and blue light
What are the photoreceptors?
The cells that convert light energy to electrical signals
What is the cornea?
The tough, transparent outer surface of the eye that is responsible for the majority of the refraction that focuses an image
What is the lens do?
It is convex in nature and enables fine tuning of focus as a person looks at objects at different distances
What happens when you have cataracts?
Cloudy spots appear in the lens, generally due to age
What happens when you have presbyopia?
There is general deterioration in long and short distance focus
What happens when you have astigmatism?
There is difficulty with either horizontal or vertical focus
What happens when you have myopia?
Your focusing power is too strong, your lens is thicker than normal and distant objects are blurry
What happens when you have hyperopia?
The lens system is too weak and near objects are hard to focus on
What is the corrective method for myopia?
Concave lenses to diverge light rays and allow stronger lens to refocus image
What is the corrective method for hyperopia?
Convex lenses to enable greater refraction to compensate for weaker lens
