Fig. 2. Schiøtz tonometry. A hollow footplate (gray) rests on the cornea, while a freely moving weighted cylinder (black) indents the cornea. The softer the eye, the greater the amount of indentation. The amount of indentation is multiplied by a lever mechanism and displayed as a “Scale Reading” at the top of the instrument. Standardized tables, based on these scale readings and considering the weight on the central cylinder, provide an estimate of IOP.