The measurement results of the commonly used non-contact tonometer are influenced by the thickness of the cornea, which is generally 530-550 um. A thin cornea will result in a low IOP measurement, while a thick cornea will result in a high IOP measurement. Corneal thickness measurement is not required for IOP measurement in general outpatient screening, but for patients with suspected glaucoma who need to confirm the diagnosis, or patients with diagnosed glaucoma who need to set a target IOP for drug treatment, corneal thickness must be measured at this time. Some hospitals now have non-contact tonometers that automatically correct for corneal thickness when measuring IOP.