There are many additional handheld tonometers of varying cost, ease of use, and availability. The Perkins MK-2 (Haag-Streit, Essex, UK) and the Kowa HA-2 (Kowa Optimed, Inc., Torrance, CA) are two handheld tonometers utilizing the Goldmann prism technique (i.e., aligning the semicircular images). They are portable, but require a familiarity with Goldmann applanation. The Accupen (Accutome, Malvern, PA) is similar to the Tono-Pen with a few differences. These include ease of use, longer battery life, and not requiring calibration before every use. The Diaton transpalpebral handheld tonometer (Bicom Inc., Long Beach, NY) is designed to measure IOP through a patient's closed eyelids.11 The Pulsair IntelliPuff (Keeler, Brownhill, PA) is the only portable, handheld, noncontact tonometer. The iCare Rebound (Tiolat Oy, Helsinki, Finland) uses a smaller zone to indent the cornea and claims not to require topical anesthesia.12 This would be particularly useful for the Emergency Department should it prove to be reliable.