Since 1912, the techniques used to determine the correct eyeglass prescription for a patient and mark uncut lenses have changed little. Lensmeters (or lensometers) are automatic analyzers designed to be used by the ophthalmologist or optometrist to fill eyeglass prescriptions as quickly and efficiently as possible. They typically have spherical and cylindrical power ranges of 0 to ±25D/±10D respectively, and cylindrical axes of up to 180 degrees, adjusted in one degree-step increments. A lensometer with an LCD display that represents lenses graphically will make the interpretation of progressive lens measurement easier. Light sources are usually green. While almost every lens analyzer enables computer control and printer connection via RS-232 or USB, some machines have built in printing capability.