The importance of the test parameters in the clinical assessment of accommodative facility

Normative data for accommodative facility have recently become available. This study investigates the effect of varying the test parameters of lens power, target size, test distance, and test duration on binocular accommodative facility. Binocular accommodative facility decreased as a function of increasing lens power and decreasing target size. Differences in response times to the plus and minus phases of the flip test were not evident under any of the conditions. Interesting effects of proximity occurred at the nearer test distance. The results show the importance of strict control of testing procedures to achieve meaningful data.