VisSys-Ia - Introduction The visual process is the...

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Introduction The visual process is the detection and translation of light into static or dynamic mental images. Specialised photoreceptor cells, rods & cones, found within the retina transduce visible light energy into electrical signals that ultimately pass to the visual cortex. Rods are responsible for monochromatic night vision and cones for high-acuity daylight colour vision. The structure of the eye modifies light before it is detected by the rods & cones. The light level is altered by changing the size of the pupil and light waves are focussed by changing the shape of the lens. Accessory structures, e.g. extraocular muscles and eyelids are essential to the visual process.
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What we see The electromagnetic spectrum extends from high energy short wavelength gamma rays to low energy long wavelength radio waves. Human visible light lies only within the range ~380-750 nm . Objects emit light (candelas m -2 ) or reflect light (lux). The eyes detect this light over an intensity range of 0.6 - 10 log cd m -2 (15 orders of magnitude). The light is detected as photons by the retinal cells - rods & cones Light Dark Rods Cones
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Anatomy of vision 2x binocular vision plus accessory structures Neural pathway for vision Optic disk - blood supply optic nerve Retina Retinal cells
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Cross-section of the eye Choroid Sclera Eyelid 3 main layers (connective tissue) (vascular) Filled with aqueous humor at an intraocular pressure 15mmHg. from the cilary body. Drains via mesh at junction of cornea & sclera into venous system via canal of Schlemm.
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A peek with an ophthalmoscope
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Retinal layers Ganglion cell axons form the optic nerve
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Cellular organisation of the retina Light Light must                 Synapses Synaptic integration
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Rods and cones. . ...are light transducers
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This note was uploaded on 08/24/2011 for the course MED 605 taught by Professor Skeen during the Fall '09 term at University of Delaware.

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VisSys-Ia - Introduction The visual process is the...

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