Visual Field Testing Periprocedural Care

Updated: Sep 01, 2016
  • Author: Meghan A Cummins, MD; Chief Editor: Hampton Roy, Sr, MD  more...
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Periprocedural Care

Equipment

None necessary; optional is a white, green, or red disc mounted on a stick.

Several perimetry devices exist: the Goldmann perimeter, tangent screen, Amsler grid, and the computerized automated perimeters are all used for perimetry testing.

Goldmann perimeter

This perimeter uses static or kinetic perimetry and tests the entire visual field. The device is a white bowl that is positioned in front of the patient. This type of device uses a light that the examiner presents from behind the bowl as the stimulus.

Tangent screen

This perimeter uses static or kinetic perimetry; however, it only tests the central 30º of the visual field. The tangent screen consists of a black screen that is placed in front of the patient. The examiner presents pins as the stimuli, in front of the screen while the patient focuses on a central target.

Amsler grid

This device tests the central 20º of the visual field. The Amsler grid is different in that it is a grid of transecting lines with a central target marked on the grid. This device is used more for testing macular function. The patient focuses their gaze on the central target and notes whether or not the lines on the grid appear wavy or if any spots on the grid appear to be missing.

Computerized automated perimeter

This perimeter tests the visual field by using only static perimetry and tests the entire visual field. Computerized automated perimeters are the newest and most sophisticated perimetry devices in existence. They also use a bowl that is placed in front of the patient. Computer generated light stimuli are created throughout the visual field, and when the patient signals visualization of each stimulus, the computer generates a numerical score related to that specific stimulus and the area of the field in which it was displayed and visualized. An overall numerical score is created at the conclusion of testing that corresponds to the degree of visual field deficit. A person's individual score may be compared to their own past scores or to the scores of patients with normal visual fields.

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Patient Preparation

Positioning

The patient should be seated in a chair or on the examination table in an adequately lit room. The examiner should assume a position directly across from the patient at an arm's length, so that their eyes align on the same horizontal and vertical plane.

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