The Eye Chapter 8
Sclera Thick, white tissue that covers the outermost part of the eyeball The “white of the eye” Central, anterior portion is clear
Cornea Transparent window through which light enters the eye Did you know… The cornea is the only tissue in the body that can be transplanted without the worry of rejection Since no blood vessels can reach the cornea, it is out of the reach of the immune system
Choroid Middle coat of the eyeball Prevents light from scattering inside the eye
Iris Band of muscles that control the size of your pupil Pigment in iris determines the color of your eyes Did you know… People with blue eyes have the least amount of pigment in their iris People with brown eyes have the most pigment in their iris
Pupil Opening in the iris that regulates the amount of light that passes into the eye Constricts: close vision & bright light Dilates: far vision & dim light
Lens Focuses light entering the eye on the retina Cataracts: Lens gets hard and opaque causing it to not be able to focus light as well resulting in hazy vision and eventually blindness
Nearsighted vs. Farsighted Lens doesn’t focus light correctly on retina Nearsighted (myopia) Distance objects appear blurry Point of focus before retina Farsighted Near objects appear blurry Point of focus behind retina
Retina Innermost layer Contains photoreceptor cells that respond to light Rods cones
Photoreceptors Rods Cones Allow us to see gray tones Provide for peripheral vision Cones 3 varieties (red, green, blue) Allow us to see colors Color blindness: caused by lack of cone type Did you know… Colorblindness is more frequent in men than women…it is a sex linked trait
Optic Nerve Photoreceptors transfer message they receive from light to the optic nerve Optic nerve sends message to brain Result is vision. Blind spot: Location where optic nerve leaves eyeball (optic disk) no photoreceptors
Aqueous Humor Anterior to the lens clear watery fluid Helps maintain pressure inside the eye so it doesn’t collapse inward Glaucoma: aqueous humor is blocked from draining and increases the pressure in the eye and compresses the retina and optic nerve
Vitreous Humor Posterior to the lens Gel like Helps maintain pressure inside the eye so it doesn’t collapse inward