What is the basis of threshold perimetry?

Threshold perimetry is based on the principle of determining the minimum intensity of light that a patient can perceive in different regions of their visual field. This is achieved by gradually increasing the brightness of a target until the patient can detect it. The method helps to map out areas of the visual field and identify any potential deficits in vision.

In the context of this question, the correct choice emphasizes the importance of light intensity and the patient’s perceptual threshold, which is central to understanding and measuring visual function. This technique is vital in diagnosing conditions that affect the retina and optic nerve, as it provides a measurable way to assess the functionality of these areas in the visual pathway.