tonometrie

Tonometry, or tonometrie, is the measurement of intraocular pressure (IOP), the fluid pressure inside the eye. IOP is a key factor in glaucoma risk and is routinely assessed during eye exams and in the management of known glaucoma. Normal IOP is commonly cited as about 10 to 21 mmHg, but individual risk depends on factors such as corneal properties and age.

Several methods are used to measure IOP. Goldmann applanation tonometry (GAT) is considered the gold standard and involves flattening a standard area of the cornea with a prism under local anesthesia. Non-contact tonometry uses a puff of air and does not require contact with the eye, offering a quick screen but with typically less precision. Rebound tonometry (eg, iCare) uses a small probe that makes brief contact and is easy to use. Other devices include Tonopen/tonometry probes, Perkins tonometer, and dynamic contour tonometry (Pascal), each with different principles and accuracy profiles. Most contact methods require topical anesthesia, whereas non-contact methods avoid anesthesia but can be more influenced by tear film and corneal properties.

Reading accuracy is influenced by corneal thickness and biomechanics, diurnal variation, posture, recent eye medication, and surface conditions. Clinically, IOP measurements are interpreted alongside optic nerve assessment, visual field testing, and imaging. Measurement carries minimal risk, mainly transient discomfort or rare corneal abrasions with contact methods. Tonometry remains a standard tool for glaucoma screening, diagnosis, and monitoring, informing decisions about treatment and follow-up.