Tonometry test - definition

Tonometry test - definition

Tonometry is a test that measures INTRAOCULAR PRESSURE (the pressure within the EYE). The primary reason for tonometry is to screen for GLAUCOMA, a condition for which elevated intraocular pressure is a characteristic symptom. Increased intraocular pressure is also common with ORBITAL CELLULITIS and GRAVES’S OPHTHALMOPATHY. Tonometry is a standard component of the OPHTHALMIC EXAMINATION.

There are several methods of tonometry. The most commonly used are

  • applanation, in which the ophthalmologist puts anesthetic drops in the eyes and then touches a device called a tonometer to the surface of the CORNEA to measure how much pressure it takes to depress the cornea
  • noncontact, or air puff, in which the person stares at a focused light while a device blows a quick puff of air at the cornea, then measures the change in reflected light from the cornea

Elevated intraocular pressure, or intraocular HYPERTENSION, requires further evaluation to detect and correct the cause. Intraocular pressure that remains elevated damages or destroys the OPTIC NERVE, resulting in total vision loss in the affected eye.

See also OPHTHALMOSCOPY; SLIT LAMP EXAMINATION.

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