Easy-to-Use with a Lightweight, Ergonomic Design The Tono-Pen AVIA tonometer, with its lightweight, ergonomic design, is an easy-to-use, handheld instrument that provides IOP readings that correlate with Goldmann tonometry. Features Does not require daily calibration Accurate and easy to use Displays an average of 10 independent readings along with a statistical confidence indicator, ensuring accurate, repeatable, and reliable tonometry results Has the same proven accuracy as the clinically trusted TONO-PEN XL, but with a more ergonomic design, four times longer lasting battery, and larger LCD screens Uses single replacement battery pack (RE52031)