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Designing for the Life Span Segment 3

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Slide 11 of 74

Slide 11 Content

Vision changes over time are complex and numerous. While hearing changes are profound, changes to the human eye and what we see and perceive condition how we will relate to an environment that continues to grow in visual complexity. Age changes to the eye include:

• Increasing opacity of the lens with severe opacity considered a "cataract."
• Flattening and stiffening of the lens, increasing farsightedness and lessening the ability to focus.
• Opacity, crazing or scratching of the cornea- defusing the light entering the eye.
• Loss of sensitivity to blue photopigmentation (only 2% blue sensitivity initially).
• Slower light adaptation (changing from low light to high lighted environments), 3 times slower at 70 than at 25.
• Lower ability to accommodate to light variance in an environment.
• A slowing of adaptation to changes in light levels in the environment.
• Loss of strength in the muscle controllers that change the shape of the lens, slowing focus or increasing the difficulty of focus.
• Yellowing of the vitreous humor or supportive fluid in the eye- affecting the perception of light color.

Narration of Slide 11

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The human eye has a specific design that has inherent limitations in capability. The human eye does not see the spectrum of color to the ultraviolet blues or the infra-reds. It cannot detect motion as well as a hawk looking for prey in a grassy field. The house fly has a greater capacity to see pattern.

Issues of acuity can be addressed by the prosthesis of eye glasses, contact lenses or, now, lasic surgery. Cataracts can also be addressed through surgery and the use of replacement prosthetic lenses. Lens replacements have also had a beneficial effect upon color perception for some older adults.

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