What does tonometry measure in the context of glaucoma?

Tonometry specifically measures intraocular pressure (IOP), which is critical in the assessment and management of glaucoma. Glaucoma is a condition characterized by damage to the optic nerve, often associated with elevated IOP. By measuring the pressure inside the eye, tonometry helps to identify individuals at risk for glaucoma or those who have the condition. Elevated IOP can lead to optic nerve damage and vision loss if not addressed.

The other options, while relevant to overall eye health and vision, do not pertain directly to what tonometry assesses. Visual acuity pertains to the clarity or sharpness of vision, corneal thickness relates to the physical attributes of the cornea, and retinal health involves the condition of the retina and its components, none of which are specifically measured by tonometry. This makes the measurement of intraocular pressure the critical focus in the context of diagnosing and monitoring glaucoma.