Background
There were individuals observing a hardening of the eye as far back as the 10th century, but it wasn't until the early part of the 19th century that many were making correlations and writing about glaucoma and increased intraocular pressure. There was no instrument to measure the actual pressure of the eye, but in 1862 William Bowman, an English ophthalmologist, recommended that a digital palpation of the eye should be part of routine eye exams (Kronfeld). By pressing on the closed eyelid, ophthalmologist could gauge the pressure of the eye in a subjective manor. This method was considered a special skill that only an ophthalmologist could correctly perform and interpret.
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In 1863, Albrecht von Graefe was the first to attempt to invent an instrument to measure and record a quantitative value for eye pressure. This initial attempt to measure intraocular pressure failed due to inconsistencies in measurement and inaccurate readings because the instrument had to be placed on the eyelid, rather than directly on the eye. Through the years following von Graefe’s attempt, there were many other unsuccessful attempts at inventing a successful tonometer.
New doors opened for the measurement of intraocular pressure in 1884 with the development of using cocaine as local anesthetic (Keeler et al. 2004). The anesthetic, applied topically, allowed for the tonometers to make direct contact with the cornea, eliminating the inaccuracies that resulted from measuring through the eyelid. This led to the next big development in measuring IOP: the corneal indentation tonometer.
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