Outline - The Eye & Sight: How does it work in the normal...

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The Eye & Sight: How does it work in the normal eye? Jason S. Ng Left-Right Conflict Look at the chart and say the COLOUR , not the word. Your right brain tries to say the color , but your left brain insists on reading the word. Optical Illusions Look at the black dot straight ahead: But once you look at them, they disappear and turn white while the surrounding dots turn gray or black. Are you seeing edges that are not there? Is it 4 Pacmen? Is it a white square blocking 4 black circles? Your eyes and brain try to fill in info. Which line is longer? Of course they are both the same. Hering Illusion Diverging lines from the distance or converging lines to a point in the distance make the two horizontal lines seem bent when they are really straight. Poggendorff Illusion Two ends of a straight line obstructed by a rectangle do not seem to line up. The bottom one seems even lower. Electromagnetic Energy
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The source? The sun. The spectrum: Gamma rays X-rays UV rays Visible spectrum (400nmVIBGYOR700nm) Infrared rays Microwaves Radio waves White light contains lots of wavelengths. Put it through a glass prism. See the dispersion angle. How do we get light? From light source through pupil until it hits the retina The human eye sees well over an enormous range of light levels: Sunny day Dusk Stars in a dark sky Eye Anatomy The eye is like a camera…only in some ways
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2 focusing componenets: cornea: 2/3’s power of eye lens: 1/3 power of eye 3 main layers: sclera: outermost tough coat of eye choroid: spongey network of blood vessels retina: innermost part of eye With age comes change: Eye size Human eye diameter: Dime to quarter 18mm at birth to 24mm in adult size Only takes ~2 years Lens changes The human crystalline lens: Gets yellower Gets stiffer Pushes forward into the anterior aqueous chamber
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Vitreous (Posterior Chamber) Changes Originally jelly-like Becomes more liquid “Floaters” Macular area Using OCT (ocular coherence topography) to map out density and surface; can see fovea pit Two kinds of photoreceptors in the retina: Rods Night Grayscale 20/200 Cones Daytime 20/20 3 types: blue green red Cones are highly concentrated in the fovea/pit In general, rods (120million): cones (6million) 15 degrees
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blind spot where optic nerve is no photoreceptors Visual impact of eye diseases Retinitis pigmentosa Can only see straight ahead; like looking into a hole Macular degeneration Image straight-ahead is unclear, missing; can see periphery Diabetic eye disease Splotches of image are missing Cataract Blurry image Glaucoma Periphery is closing in Eye movements Muscles involved: Trochlea Superior oblique Superior rectus Annulus of Zinn
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Lateral rectus Medial rectus Inferior rectus Inferior oblique 9 cardinal positions of gaze: UL, UC, UR ML, MC, MR DL, DC, DR Eye movements must be: Stable (1 eye) Precise (1 eye) Coordinated (both eyes)
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This note was uploaded on 09/24/2009 for the course OPTOM c10 taught by Professor Levi during the Spring '08 term at Berkeley.

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Outline - The Eye & Sight: How does it work in the normal...

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