Which of the following is a measure of intraocular pressure?

Tonometry is the procedure specifically designed to measure intraocular pressure (IOP) within the eye. This measurement is critical in assessing the risk of glaucoma and other ocular conditions. Various types of tonometers exist, such as applanation tonometers and non-contact tonometers, each employing different techniques to determine the pressure exerted by the fluid inside the eye.

Other options serve different purposes related to eye health. Ophthalmoscopy is used for viewing the interior of the eye, including the retina, while perimetry assesses the visual fields to identify peripheral vision loss. Refraction involves testing for vision correction needs and determining the appropriate prescription for glasses or contact lenses. These other tests do not address intraocular pressure specifically, making tonometry the correct choice in the context of measuring IOP.