Comparing methods of determining addition in presbyopes.

BACKGROUND The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients. METHODS Sixty-nine healthy subjects with a mean age of 51.0 years (range 40 to 60 years) were studied. Tentative near additions were determined using seven different techniques: dynamic retinoscopy, amplitude of accommodation (AA), age-expected addition, binocular fused cross-cylinder with and without myopisation, near duochrome, and balance of negative and positive relative accommodation. The power of the addition was then refined to arrive at the final addition. RESULTS The mean tentative near additions were higher than the final addition for every procedure except for the fused cross-cylinder without initial myopisation and age-expected addition methods. These biases were small in clinical terms (less than 0.25 D) with the exception of the AA procedure (0.34 D). The intervals between the 95% limits of agreement differed substantially and were always higher than +/-0.50 D. CONCLUSIONS All the techniques used displayed similar behaviour and provided a tentative addition close to the final addition. Due to the wide agreement intervals observed, the likelihood of error is high and supports the idea that any tentative addition has to be adjusted according to the particular needs of each patient. Among the methods examined here, we would recommend the age-expected procedure, as this technique produced results that correlated best with the final addition.