Single figure indices for the steady-state accommodative response.

The slope of the regression line fit is often used to characterize an accommodation response-stimulus curve. It is argued that comparisons based on this parameter alone may be misleading, as also may be those using the intercept or correlation coefficient of the regression line. It is suggested that it would be more useful to compare curves on the basis of a combination of all three regression line parameters, together with the stimulus interval over which the fit is derived. A new parameter, the accommodative error index which is effectively the mean of the magnitude of the response error divided by the correlation coefficient, is proposed to achieve this.