When evaluating accommodation and binocular vision, optometrists measure the amplitude and the response facility. Amplitude testing provides information about how much accommodation and vergence are available, and facility testing provides information about the speed of the response and ability to sustain the response over an extended period of time.
Testing Procedure: While holding the vertical column of letters the appropriate distance from the patient (see picture), alternate lenses or prisms in front of a patient's eye and ask the patient to report when they achieve single, clear vision of the vertical bar of characters on the fixation target. The number of responses that occur in one minute should be recorded.
Before development of the Fixi-Tic, facility testing was challenging for clinicians. The clinician must hold the fixation target, move the vergence facility prism or accommodative flippers, count the number of responses, and also time the test while observing the patient’s eyes. With one hand holding the target, one holding the prism or flippers, and the clinician's attention focused on the patient, the challenge is to accurately time the test (1 minute) without the aid of another person. Enter the Fixi-Tic. The Fixi- Tic is a timer that slides onto the fixation stick. It is easy to use, ergonomically designed, and it beeps once a minute of time has expired. By holding the fixation stick and providing timing functionality for the clinician, the Fixi-Tic greatly improves the accuracy of results for this test.