Eye Flashcards
Sclera
Tough supporting wall
Cornea
Transparent outer layer at front
Refracts light into eye
Iris
Contains muscles to control diameter of pupil
Controls how much light enters eye
Lens
Focuses light on retina
Retina
Contains receptor cells sensitive to light intensity and colour
Pupil
Hole in middle of eye
Ciliary muscles and suspensory ligaments
Control shape of lens
Optic nerve
Carries impulses from receptors on retina to brain
What happens when very bright light is detected?
Circular muscles contract
Radial muscles relax
Pupil smaller
What happens when dim light is detected?
Radial muscles contract
Circular muscles relax
Pupil widens
To look at near objects
Ciliary muscles contract so suspensory ligaments slacken
Lens becomes fat
Increases amount of refracted light
To look at distant objects
Ciliary muscles relax so suspensory ligaments pull tight
Lens becomes thin
Smaller amount of light refracted
Hyperopia
Long-sighted
Unable to focus on near objects
Lens is wrong shape/eyeball too short
Images brought into focus behind retina
How to correct long-sightedness
Convex lenses
Myopia
Short-sighted
Too much light/eyeball too long
Images focussed in front of retina
