A nurse is reinforcing teaching about a tonometry examination with a client who has manifestations of glaucoma. Which of the following statements should the nurse include in the teaching?

Choice A rationale This diagnostic procedure utilizes a device to apply a small amount of pressure to the corneal surface to determine the resistance of the globe. By measuring how much the cornea indents or flattens, the tool calculates the internal pressure of the eye in millimeters of mercury. This is the primary screening method for detecting ocular hypertension, which is a major risk factor for the development of optic nerve damage and subsequent vision loss in patients. Choice B rationale Inspection of the optic disc is typically performed using an ophthalmoscope during a funduscopic examination, not through this specific pressure test. Funduscopy allows the clinician to visualize the cup-to-disc ratio and look for signs of cupping or atrophy. While assessing the optic nerve is crucial for managing the disease, it involves direct visualization of the posterior segment of the eye rather than the measurement of fluid tension within the anterior chamber of the eye. Choice C rationale While this test identifies elevated pressure, it does not by itself distinguish between open-angle and angle-closure types. Differentiation requires gonioscopy, which allows the provider to visualize the drainage angle between the iris and the cornea. The pressure measurement is a quantitative data point that suggests the presence of the disease but does not provide the anatomical detail necessary to classify the specific mechanical cause of the fluid backup or the narrowness of the angle. Choice D rationale Evaluation of peripheral vision is conducted through visual field testing or perimetry. This assesses the functional loss of the retinal periphery, which often occurs as the disease progresses. This pressure-based test is a physiological measurement of tension rather than a functional assessment of the visual cortex or retinal sensitivity. While both tests are part of a comprehensive ocular workup, they measure entirely different aspects of eye health and disease progression in the patient.