B5 - The eye and correcting vision defects
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What is the Sclera
Supporting wall of the eye
What is the Cornea
Transparent outer layer found at the front of eye, refracts light into eye
What is the Iris
Contains muscles that allow it to control the diameter of the pupil (how much light enters eye)
What is the lens
Focuses light on to retina which contains receptor cells sensitive to light intensity and colour
What is the shape of the lens controlled by
Ciliary Muscles and Suspensory Ligaments
What does the Optic Nerve do
Carries impulses from receptors on the retina to the brain
What happens when receiving very bright light
Circular muscles in iris contract and radial muscles relax
What happens when receiving dim light
Radial muscles contract and circular muscles relax
Focus on near objects
Ciliary muscles contract which slackens suspensory ligaments Lens becomes more curved -Increases refraction of light
Focus on distant objects
Ciliary muscles relax which allows suspensory ligaments to tighten Makes lens less curved -Refracts light less
Lens or eyball of Long-sighted
Lens doesn’t refract light enough or eyeball is too short Images of near objects are brought into focus behind the retina
What glasses lens do long-sighted wear
Convex lenses
Medical term for long-sighted
Hyperopia
Lens or eyeball of Short-Sighted
Lens refracts light too much or eyeball is too long Images of distant objects are brought into focus in front of the retina
What glasses do short-sighted wear
Concave lenses
Medical term for short-sightedness
Myopia Laser eye surgery Replacement lens surgery
3 Treatments for vision defects
Contact lenses Laser eye surgery Replacement lens surgery