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How Do Glasses Work?

{ DO } GLASSES WORK 50.0 20.0 50.0 8.0 34.5 34.5 140.0 75% of Americans need corrective lenses to keep their surroundings in focus, but understanding how glasses work begins with the mechanics of the eye { HOW THE H EYE FOCUSES LIGHT Pupil Allows light into the back of the eye Cornea Top layer of the eye where all light must pass through Optic Nerve L IG HT Lens Works with the cornea to fine-tune vision Retina Complex layer of cells that react to light WHAT HAPPENS WHEN YOU LOOK AT THE WORLD AROUND YOU? Light Image translated Retina Scattered light merges together and is focused on the retina Images must shrink and curve to match the shape of the retina Reaction to light is relayed from the retina to the brain and is translated into an image Light rays are focused directly on the retina for those with perfect vision, but eyeglasses can bend the light, so most everyone can have 20/20 vision H WHEN VISION GOES ASKEW H GLASSES TO THE RESCUE These common vision problems occur when the eye cannot focus an image onto the retina MYOPIA [ NEARSIGHTEDNESS ] Focal Point Retina Occurs because the image comes into focus before it reaches the retina Close objects are in focus Distant objects are out of focuS HYPEROPIA [ FARSIGHTEDNESS ] Focal Point Occurs because the image doesn't come into focUS before it gets to the retina Close objects are out of focuS Distant objects in focus ASTIGMATISM Lens Multiple Focal Points Oval Shaped Cornea Shape of the lens or cornea is distorted so light makes two focal points instead of one More curvature in one direction than in another results in blurred vision at all distances LENSES CAN BE CUT TO BRING THE IMAGE CLOSER, FURTHER AWAY, OR CORRECT OTHER VISION PROBLEMS LIKE DOUBLE VISION { HOW DO LENSES CORRECT H VISION P ROBLEMS? WHAT IS A LENS? LENS Prisms are always thicker at one end and light passing through it is bent/refracted toward the thicker end LIGHT Two rounded prisms joined together TWO MAIN TYPES OF LENSES Convex/Plus (+) lens [ Nearsightedness ] Lens bends the light Light Corrected focal point ..... 2 Bends the light towards the bottom and top of the lens, pushing the focal point back to the retina The stronger the lens, the closer the focal point is to the lens Concave/Minus (-) lens [ Farsightedness ] Lens bends the light 10 Light Corrected focal point Spreads the light away from the center of the lens and moves the focal point up The stronger the lens, the farther the focal point is from the lens WEARING THE CORRECT TYPE AND POWER OF LENS MAKES UP FOR YOUR EYE'S INABILITY TO PROJECT LIGHT ON YOUR RETINA LENS STRENGTH LENS TYPE Diopters (D) express the lens strength and indicate how much the light is bent Plus (+) or minus (-) sign before the dioper indicates lens type Higher diopters indicate stronger lenses Plus and minus lenses can be combined, so the algebraic sum is the lens type +1D -4D 1D = 1 m 2D = 2 m 3D = 3 m +1.00D lens + -4.00D lens = -3.00 lens LENS SHAPES SPHERICAL LENS CYLINDRICAL LENS COMPOUND LENS Used to correct astigmatism Curve is the same all over the surface of the lens Typically used to focus incoming light into a line Included spherical and a cylindrical component { SO HOW DO YOU H READ A PRESCRIPTION? OPTOMETRIST SHORTHAND Optometrist Shorthand OD 2.50 - 1.50 X 123 plus +2.00 OD = Right eye OS = Left eye Spherical base Cylinder strength and type [-1.50D cylinder] Cylinder axis orientation (x means "at") Strength of bifocal segment and type strength and +/- type [123 degrees] [Bifocal segment of +2.00D] [+2.5D] SOURCES FRAMESDIRECT.COM premi um e y e we ar DEVELOPED BY N NOWSOURCING

How Do Glasses Work?

shared by NowSourcing on Mar 07
Have you ever wondered how your glasses correct your vision? It's both complicated physics and simple math.


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