• 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.
Structure Function
Sclera Supports and protects delicate photocells
Cornea Refracts light towards pupil
Aqueous Humour Supplies cornea with nutrients and refracts light
Choroid Layer Contains pigments that prevent scattering of light in the eye by absorbing stray light; also contains blood vessels
Iris Regulates the amount of light entering the eye
Pupil The opening in the iris that allows light into the eye
Lens Focuses the image on the retina
Ciliary muscles Change the shape of the lens
Vitreous humour Maintains the shape of the eyeball and permits light transmission to the retina
Retina Contains the photo receptors
Fovea Centalis Most light sensitive area of the retina; contains only cones

Vision Defect Cause Treatment
Glaucoma Build up of aqueous humour in the anterior chamber of the eye
Cataract When the lens or cornea become opaque, preventing light from passing through
Astigmatism Abnormal curvature of surface of the lens or cornea Glasses that contain an astigmatic lens
Nearsightedness (myopia) Condition that occurs when the image is focused in front of the retina Glasses 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

author avatar
William Anderson (Schoolworkhelper Editorial Team)
William completed his Bachelor of Science and Master of Arts in 2013. He current serves as a lecturer, tutor and freelance writer. In his spare time, he enjoys reading, walking his dog and parasailing. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2024 | Creative Commons 4.0

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