OPTICAL INSTRUMENT • DICTIONARY ONE.COM • Definition of Optical instrument

... stepped forward and applied his eye to the lens. I suspect it to have been shut most of the time, for I observe a good many elderly people adjust the organ of vision to any optical instrument in that way. I suppose it is from the instinct of protection to the eye, the same instinct as that which makes the raw militia-man close it when he pulls the trigger of his musket the first time. He expressed himself highly gratified, however, with what he saw, and retired ...

— The Poet at the Breakfast Table • Oliver Wendell Holmes, Sr.

... optical instrument, contrived to give to the eye a large appearance of many objects which ...

— The Illustrated London Reading Book • Various