The Eye Flashcards
Sclera
External layer of the eye that is white, tough, and fibrous. It protects and supports the eyeball.
Cornea
Transparent part of the sclera at the front of the eye that bends light rays into the eye.
Choroid
Absorbs scattered light not detected by photoreceptors and contains blood vessels
Iris
Regulates amount of light that enters the eye. Adjusts size of pupil- adaptation
Pupil
the opening for light to enter the inner eye
Retina
Thin layer that contains photoreceptors- rods and cones
Rods
Photoreceptors sensitive to light intensity
Cones
Photoreceptors sensitive to different wavelengths of light (colour vision)
Optic Nerve
Transmits sensory information back to the brain
Aqueous Humour
A clear, watery fluid in the anterior chamber that maintains the shape of the cornea and provides oxygen and nutrients to surrounding cells
Vitreous Humour
A clear, jelly-like fluid in the posterior chamber that helps maintain the shape of the eyeball, and supports surrounding cells
Ciliary Muscle
Changes shape of lens in order to focus
Fovea Centralis
Contains a high density of cones and provides acute vision
Lens
Focuses light rays on the fovea centralis
Glaucoma
Happens when the ducts that drain the aqueous humour become plugged. This can lead to pressure building up in the eye and rupturing the blood vessels. Due to lack of oxygen and nutrients, the cells of the eye then deteriorate.
Cataracts
As the lens ages, protein structures degenerate making it opaque and light cannot pass through. The condition can cause grey-white spots. Lens can sometimes be surgically replaced
Astigmatism
An uneven curvature of part of the cornea. Since the cornea is asymmetrical it cannot bend light rays to meet at the correct focal point, vision is blurred.
Hyperopia
Farsightedness. Cannot focus on objects nearby because the eyeball is too short. The light rays do not meet before reaching the retina so the image is focused behind the retina. Convex lenses can correct this by bending light rays at a sharper angle.
Colour Blindness
An inherited condition that results in nonfunctional or deficient cone function; inability to see certain colours such as red, green, or blue
Myopia
Nearsightedness. Cannot focus on objects far away because eyeball is elongated. Focus of light falls in front of the retina. Concave lenses can correct this by diverging light rays so the image lands on the retina.
Blindspot
The area where sensory fibres come together to form the optic nerve at the back of the eyeball. It is deficient in rods and cones.
Tapetum
A layer in the choroid that increases absorption of light to stimulate photoreceptors in dim conditions. Reflective - cat eyes seem to glow.
Ganglion cells
Special sensory neurons that communicate with bipolar cells in the retina to transmit a nerve impulse to the brain. These cells have long axons that converge at the back of the eye to form the optic nerve.
Iodopsin
The general name for any of the three visual pigments found in cone cells that is stimulated by light to initiate a nerve impulse
