What is Perimetry?
Our visual world is composed of images of colors, textures, edges and contrasts. In addition, these images may be moving or flickering. The goal of visual testing is to quantitate of these functions.
Traditionally we have tested visual function as visual acuity - the capacity to discriminate the fine details of objects and visual field - the portion of space in which objects are visible at the same moment during steady fixation of gaze in one direction. Color vision testing, flicker sensitivity, contrast sensitivity, pupillary responses and motion testing are some of the other methods of quantitating vision.
Perimetry is the systematic measurement of visual field function. The two most commonly used types of perimetry are Goldmann kinetic perimetry and threshold static automated perimetry. With Goldmann or "kinetic" perimetry, a trained perimetrist moves the stimulus; stimulus brightness is held constant. The limits of the visual field are mapped to lights of different sizes and brightness.
With threshold static automated perimetry, a computer program is selected. The most commonly used one tests the central 30° of the visual field using a six degree spaced grid. This is accomplished by keeping the size and location of a target constant and varying the brightness until the dimmest target the patient can see at each of the test locations is found. These maps of visual sensitivity, made by either of these methods, are very important in diagnosing diseases of the visual system. Different patterns of visual loss are found with diseases of the eye, optic nerve central nervous system.
Read more about perimetry
Conventional Perimetry. Part I: Introduction, Basic Terms. (pdf)
As Slightly modified translation of:
U. Schiefer, J. Pätzold, F. Dannheim: Konventionalle Perimetrie. Teil I: Einführung – Grundbegriffe. Der Ophthalmologe 2005, 102(6):627-646.
With kind permission from Springer Science+Business Media, Heidelberg, Germany