Unit 2 Notes: Vision Tuesday

(1) Outer Layers of The Eye 3 layers surrounding inner fluid:3 layers surrounding inner fluid: –Outermost = Sclera –Middle Tissue = Choroid –Innermost = Retina Inner Fluid = HumorInner Fluid = Humor –Humor increases inner pressure –Maintains eyeball shape –Glaucoma  Increase in Pressure

(2) The Sclera White tissue on the outside Contains the cornea:Contains the cornea: –Light enters the eye here –Directly connected to nerve endings

(3) The Choroid Made of darker pigments:Made of darker pigments: –Keeps light rays inside the eye Contains the ciliary body and the iris:Contains the ciliary body and the iris: –Ciliary Body = Lens is attached to this Tissue –Iris = Pigmented portion of your eye Muscle Contract = Decrease Light Inflow Relax = Increase Light Inflow

(4) The Retina Contains Photoreceptors (Rods & Cones)Contains Photoreceptors (Rods & Cones) –Electrical signal passes from receptors  optic nerve  brain Rods = Shades & Grays Cones = Colors –Blue-Yellow –Green –Red-Green Impulses from multiple receptors  In Between Colors

(5) Color Blindness MonochromacyMonochromacy –All cones are missing or damaged –No color –Still can see shades (rods function) DichromacyDichromacy –Red-Green  Colors look the same –Blue-Yellow  Colors look the same

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(6) Light Refraction & The Lens Light passes through the cornea and Lens to enter eyeball…Light passes through the cornea and Lens to enter eyeball… –Light passing thru different mediums  Refraction –Refraction = Bending of light Eye controls amount of light entering with Iris + Lens:Eye controls amount of light entering with Iris + Lens: –Ciliary Body Contraction  Closing In of Iris  Decreased Pupil Size –Ciliary Body Relaxes  Widening of Iris  Increased Pupil Size

(7) Types of Eyesight Emmetropia = Perfect Eye Sight Myopia = Nearsighted Hyperopia = Farsighted Astigmatism = All Messed Up

(8) Myopia Cornea too convex or bulging…Cornea too convex or bulging… –Light is over focused and refracted before hitting retina –Light rays are scattered when hitting retina –Blurred Vision Solution:Solution: –Concave Lens (thinner in middle) –Decreases refraction, Spreads out Light Rays

(9) Hyperopia Cornea is too concave (flattened out): –Light is not focused or refracted enough –Light rays are scattered when hitting retina –Blurred Vision Solution: –Convex Lens (thicker in middle) –Refracts and Focuses light before hitting eye

(10) Astigmatism Uneven cornea or lens:Uneven cornea or lens: –Causes blurred vision because light is refracted unevenly –Astigma = Not A Point Solution:Solution: –Concave + Convex Lens –Cancels out Uneveness

Optical / Visual Illusions Not all are fully understood Unusual combinations of color, shades and angles confuses our brain Lack of “stable”, familiar surroundings confuses our brain Our brains “fill in” areas we do not know or see to stabilize the visual

Science & Perception

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