Comparison of disparometer fixation disparity curves as measured with and without the phoropter

Traditionally, Disparometer fixation disparity curve (FDC) measurement has been performed using a phoropter, although more recently some clinicians have suggested that the Disparometer be used outside the phoropter. Whereas vertical fixation disparity (FD) measurements have been found to correlate well when obtained with and without a phoropter, there is currently no evidence that horizontal FDC's are similar in the two testing situations. A FDC was plotted for 30 visually asymptomatic young adults both in and out of the phoropter. Statistical analysis revealed no significant differences between results on the basis of curve type, slope, y- or x-intercept; however, noteworthy individual variations did occur. Therefore, we conclude that consistency of testing method is important when serial curves are plotted for a given patient. Although each method has some advantages and disadvantages, neither is clearly superior based on this study.