Are eyes spheres?

Is the Earth a sphere?

More or less. It depends how accurately and detailed you want to measure them. The globe (eyeball) is shaped more like a pear: It has a "bulge" on the front where the cornea, iris, and natural lens are. The curvature of the corneal surface is not perfectly spherical either -it is actually what is called a "spheroid:" roughly the shape of a rugby ball. To be even more specific, the cornea's curve (like that of the eyeball), is steepest at the center of its surface and gets flatter as you go out to the sides (the limbus). There are optical reasons why this works better in vision than a pure sphere. Anybody who has done photography and knows about "aspheric lenses" will understand.

Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic

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