Repeatability of clinical measurements of the amplitude of accommodation.

In order to determine whether a significant change has occurred in a clinical parameter, it is essential to assess the repeatability of the measurement procedure. Accordingly, the present study has examined the repeatability of three techniques for evaluating the subjective amplitude of accommodation. Clinical amplitudes were determined using the push-up, push-down and minus lens procedures in 13 young individuals (mean age: 24.3 years) on five separate occasions. The standard deviation (SD) of the five examinations was calculated for each individual and the mean values for the population sample determined. The mean SDs for the push-up, push-down and minus lens techniques were equivalent, with 95% confidence limits of approximately 1.4 D being observed for all three procedures. Furthermore, the mean amplitude recorded using the push-up technique was significantly higher than that observed for the other two procedures. It is concluded that a change of at least +/- 1.50 D should be adopted as the minimum significant shift in amplitude of accommodation for this group.