What instrument is primarily used to measure intraocular pressure?

The tonometer is the primary instrument used to measure intraocular pressure (IOP), which is a critical factor in diagnosing and managing conditions such as glaucoma. Intraocular pressure is the fluid pressure within the eye, and measuring it helps assess the health of the optic nerve and the overall condition of the eye.

Tonometers come in various forms, including applanation tonometers, which flatten a portion of the cornea to measure pressure, and non-contact tonometers, which use a puff of air to assess IOP. The ability to accurately measure IOP is essential for evaluating patients at risk for glaucoma and for monitoring those already diagnosed with the condition.

The other instruments serve different purposes; a slit lamp is primarily used for examining the anterior segment of the eye in detail. An ophthalmoscope is utilized for viewing the retina and the internal structures of the eye, providing essential information for diagnosing retinal conditions and other ocular diseases. An autorefractor is used to measure a person's refractive error to determine the proper prescription for glasses but does not assess intraocular pressure. Hence, the tonometer remains the critical device for measuring IOP.