Lens Distance From Eye
The overall size of the lens is controlled by how far the lens is positioned away from the eyes. A closer distance allows for a smaller lens, but there is a limit on how close eyeglass lenses in a frame can be to the eye, imposed by the eyelashes and eyelid.
Contact lenses placed directly on the cornea are physically larger than the pupillary region, and have a ring of extra unused material around the outer perimeter that simply helps to center the lens on the cornea.
Eyeglass lenses need to be larger the further away they are from the eye. Very large lenses in a double-bridge frame do not necessarily provide greater peripheral vision, due to the nose rest holding the lenses slightly further away from the eyes than with smaller lens frames.
Read more about this topic: Corrective Lens
Famous quotes containing the words distance and/or eye:
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—Benjamin Franklin (1706–1790)
“The eye by long use comes to see even in the darkest cavern: and there is no subject so obscure but we may discern some glimpse of truth by long poring on it.”
—George Berkeley (1685–1753)