Concept explainers
Light that enters your eyes is focused to form an image on your retina. The optics of your visual system have a total refractive power of about +60 D - about +20 D from the lens in your eye and + 40 D from the curved shape of your cornea. Surgical procedures to correct vision generally do not work on the lens; they work to reshape the cornea. In the most common procedure, a laser is used to remove tissue from the center of the cornea, reducing its curvature. This change in shape can correct certain kinds of vision problems.
59. Suppose a woman has a far point of 50 cm. How much should the refractive power of her cornea be changed to correct her vision?
A. –2.0 D
B. –1.0 D
C. +1.0 D
D. +2.0 D
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