Today, eye pressures are recorded at annual eye examinations as a screener and risk assessment for glaucoma; this however, has not always been routine, or even possible until the early 1900s. This website addresses my research on the role the development of indentation tonometry had in the medical understanding, diagnosis, and treatment of glaucoma in the early to mid-20th century. Tonometry is the procedure eye care professionals use to determine and monitor intraocular pressure. The correlation between a harden eye and glaucoma has been present for centuries, but it wasn’t until the invention of the tonometer that doctors were able access intraocular pressure in a much more accurate and quantitative method than in the past. The adoption of the indentation tonometry was influenced by the standardization of medical care in the early 20th century. This had both positive and negative effects on the diagnosis of glaucoma. A high intraocular pressure reading from the tonometer defined the disease. Many medical practitioners began to solely use the intraocular pressure reading to diagnosis glaucoma until the 1960s, when population studies began to investigate the true correlation of intraocular pressure and the development of glaucoma.