Which statement best describes the purpose of tonometry?

The purpose of tonometry is to measure intraocular pressure (IOP) within the eye. Maintaining the correct level of IOP is essential for preserving the health of the optic nerve and preventing conditions such as glaucoma. This measurement helps eye care professionals monitor, diagnose, and manage various eye diseases that may lead to vision loss if untreated.

Tonometry is typically performed during an eye examination and can involve different methods, such as applanation tonometry or non-contact tonometry (often referred to as the "air puff" test). These techniques help provide a precise assessment of the eye's pressure, which is a crucial component in evaluating the overall health of the eye.

In contrast, the other statements focus on different aspects of eye health that are not the primary goal of tonometry. Assessing peripheral vision, evaluating the drainage of aqueous humor, and identifying cataract formation involve separate diagnostic methods and considerations that do not pertain directly to measuring intraocular pressure.