Projection or focusing

The difference between the lens of the eye and and ordinary optical lens is that the former is flexible, its shape being controlled by the tension of muscle fibers. These muscles allow the lens to become flatter or thicker in order to focus on distant or near objects.

Figure- The extrinsic muscles of the eye viewed from above (from Fischler and Firschein, 1987)
Figure- Optical representation of the eye looking at a tree: point C is the optical center of the lens (from Gonzalez and Woods, 1992)


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Last modified on April 05, 1999, G. Scott Owen,