a device that requires skill for proper use

a transparent optical device used to converge or diverge transmitted light and to form images

(plural) an optical instrument designed for simultaneous use by both eyes

an optical instrument for examining the inside of the esophagus

an optical instrument used by jewelers; has one or more lenses and is used to view features not readily seen

an optical instrument that provides a view of an otherwise obstructed field

an optical instrument that projects an enlarged image onto a screen

a transparent optical device used to converge or diverge transmitted light and to form images