The use of tonometry for the measurement of intraocular pressure (IOP) occupies a key position among those tests that optometrists routinely carry out in practice. Tonometry’s importance is inextricably associated with glaucoma, notably primary open angle glaucoma (POAG). This link with glaucoma can be traced back for more than 100 years, but the nature of the link is regularly modified as we learn more about glaucoma in all its forms. For example, over the past 25 years elevated IOP has shifted from being an essential part of the definition of POAG to its current position where elevated IOP no longer features in modern definitions of the disease, reflecting the high proportion of those with POAG (estimated to be approximately 40 – 50% of those diagnosed) who suffer from normal tension glaucoma (NTG). Instead, elevated IOP is now regarded a major glaucoma risk factor. These changes do not reduce the importance of IOP for POAG because, unlike other risk factors, IOP is modifiable with drugs or surgery and, as a result, reducing IOP is the cornerstone of POAG management around the world.
Accurate tonometry is the only means at our disposal to detect the important glaucoma risk factor and this article, by Professor David F Edgar BSc FCOptom, reviews different methods.
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