Therefore, mounting lenses required a special preparatory procedure.

The tiny lenses of a conventional system required supporting rings that would obscure the bulk of the lens' area.

The lenses require organic materials that are biologically safe and also use inorganic material for the electronic circuits.

The lens is metabolically active and requires nourishment in order to maintain its growth and transparency.

The lenses will require approval by the Food and Drug Administration before they can be sold.

The problem was, of course, that such a lens required as much light as she could find.

These lenses require moving parts, and as moving parts become smaller, overcoming friction between them is increasingly difficult.

However, not all such lenses require the shorter back focus, and may feature the standard EF mount.

Soft lenses are immediately comfortable, while rigid lenses require a period of adaptation before full comfort is achieved.

Other lenses require regular cleaning and disinfecting to prevent surface coating and infections.