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Unformatted text preview: K IN 4512 Exam 3 Chapter 8 Movement and the Changing Senses Understanding the Mechanics of Vision Light rays converge and meet at a focal point (Retina) Cornea and fluids in the eye retract and bend The lens can adjust the focal point by changing shape When the ciliary muscles relax the lens flatten and when they contract Sight Accommodation: adjusts to variations in distance; does this at varying lights Retina: has two proprioceptors • Rods: vision and low illumination; night vision • Cones: responsible for color vision and acuity Macula: yellow circle, in and around the retina; less than 5% of the retina; sharp vision is possible when light converges with this • Fovea: center of the macula; point of best vision for acuity is when light converges with this part of the eye; cone cells are concentrated at the fovea but there is an absence of rod cells Ciliary Muscle: change the shape of the lens Physical Development of the Eye The eye develops as an outgrowth of the forebrain Part of the central nervous system (6 nerves) At birth - The eye is hyperopic (light focuses beyond the retina) • Retina contains mostly rod cells At 1 month postnatal: Cone cells start to appear; start to see some colors At 8 months postnatal: Macula is mature Refraction problems and corrections Visual Acuity Static Visual Acuity: target and the performer are stationary Snellen Eye Chart: 20/20 what you see at 20 feet is what normal people see at 20 feet Birth: 20/300; 6 months 20/200 and 1 year 20/ 50 and 4-5 20/20 Dynamic Visual Acuity: ability to see in detail moving objects Occulomotor system: catch and hold an object image in the eyes fovea Improves between 6-20 & declines after 25 Visual Acuity and Exercise Aerobic activities appear to improve visual acuity for up to two hours post-exercise Increase in acuity due to increase in blood flow and oxygenation to the eye Visual Acuity and Aging Age-related eye diseases (ARED) are the leading cause of loss of visual acuity Conditions/diseases • Age-related macular degeneration (AMD) ♦ Senile macular degeneration or Age-related maculopathy ♦ Loss of central vision ♦ Dry form: break down of light sensitive cells in the macula, central vision affected, not allowed to drive, trouble reading ♦ Wet form: new blood vessels that form behind the retina and they start to leak and destroy the macula • Glaucoma ♦ Leading cause of loss in visual acuity and blindness ♦ High pressure in the eye, loss of peripheral vision and eventually loss of central vision • Cataracts: clouding of the eye lens, causes glare, fading of color, increased need for light for reading, risk is increased with alcohol, smoking, and long term exposure to UV rays • Senile miosis: 30-60 there is a normal loss; decrease in resting diameter of the pupil by age 60 the amount of light that can come in is about a 1/3 of what could...
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- Spring '09
- Visual acuity, plantar reflex, Primitive reflexes, Palmar Grasp Reflex