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The Eye

The Eye. Refraction by the Cornea & Lens. Image focused on retina is inverted & reversed from left to right Brain learns to work with that information 75% of Refraction is done by cornea -- rest is done by the lens

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The Eye

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  1. The Eye

  2. Refraction by the Cornea & Lens • Image focused on retina is inverted & reversed from left to right • Brain learns to work with that information • 75% of Refraction is done by cornea -- rest is done by the lens • Light rays from > 20’ are nearly parallel and only need to be bent enough to focus on retina • Light rays from < 6’ are more divergent & need more refraction • extra process needed to get additional bending of light is called accommodation

  3. Correction for Refraction Problems • Emmetropic eye (normal) • can refract light from 20 ft away • Myopia (nearsighted) • eyeball is too long from front to back • glasses concave • Hypermetropic (farsighted) • eyeball is too short • glasses convex (coke-bottle) • Astigmatism • corneal surface wavy • parts of image out of focus

  4. Tunics (Layers) of Eyeball • Fibrous Tunic(outer layer) • Vascular Tunic (middle layer) • Nervous Tunic(inner layer)

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