• Rods respond to low intensity light; cones, which require high intensity light, identify colour.
  • The blind spot is where the optic nerve attaches to the retina; no rods or cones are present in this area, so there’s an absence of photosensitive cells
  • Ciliary muscles change the shape of the lens. A thicker lens permits the greater bending of light for viewing near objects, while a more flattened lens is used to view distant objects.
  • Accommodation: adjustments made by the lens and pupil of the eye for near and distant objects. With age, the layers of transparent protein covering the lens increase throughout your life, making the lens harder. As the lens gets harder, it loses flexability.
StructureFunction
ScleraSupports and protects delicate photocells
CorneaRefracts light towards pupil
Aqueous HumourSupplies cornea with nutrients and refracts light
Choroid LayerContains pigments that prevent scattering of light in the eye by absorbing stray light; also contains blood vessels
IrisRegulates the amount of light entering the eye
PupilThe opening in the iris that allows light into the eye
LensFocuses the image on the retina
Ciliary musclesChange the shape of the lens
Vitreous humourMaintains the shape of the eyeball and permits light transmission to the retina
RetinaContains the photo receptors
Fovea CentalisMost light sensitive area of the retina; contains only cones

Vision DefectCauseTreatment
GlaucomaBuild up of aqueous humour in the anterior chamber of the eye
CataractWhen the lens or cornea become opaque, preventing light from passing through
AstigmatismAbnormal curvature of surface of the lens or corneaGlasses that contain an astigmatic lens
Nearsightedness (myopia)Condition that occurs when the image is focused in front of the retinaGlasses that contain concave lenses
Farsightedness (hyperopia)Eyeball is too short

Occurs when the image is focused behind the retina

Glasses that have a convex lens

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