Christiaan Huygens built excellent lenses in the 17th century, but his telescopes lacked sharpness in comparison with what was possible at that time. In a recent study, Dr. Alex Pietrow, researcher at the Leibniz Institute for Astrophysics Potsdam (AIP), investigated Huygens' calculations and has concluded that the Dutch astronomer and mathematician was probably near-sighted and would have needed eyeglasses to improve his telescopes.