Perimetry is a visual field test that measures a person's peripheral vision. It helps detect any changes or loss in vision, which can indicate various eye conditions, such as glaucoma or retinal diseases. During the test, patients focus on a central point while lights or objects are presented in their side vision. The results are plotted on a chart, showing areas where vision is normal or diminished. This information assists eye care professionals in diagnosing and monitoring eye health. Regular perimetry tests can be crucial for early detection and management of vision-related issues.