Visual symptoms associated with computer use occur frequently in the general population producing discomfort for extended periods of time. They are strongly associated with ocular surface disease. Therapeutic regimens need to be developed for this widespread condition.

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Purpose: Dynamic retinoscopy (DR) is a procedure for assessing the accommoda-tive response using a standard clinical instrument. The present study compared measurements of the amplitude of accommodation (AA) obtained using this technique with two subjective methods (modified push-down and minus lens). Additionally, the expected ranges for AA when measured by DR were determined. Method: AA was measured in 1298 subjects between 5 and 60 years of age using the three techniques described above. Subjects were grouped into 5-year bins, and a descriptive univariate analysis of the data performed. Goodness-of fit plots were constructed to examine the overall model fit. Centile curves were calculated from the final model. Results: Mean values of AA obtained using DR were significantly lower than for the two subjective techniques. For the DR findings, no significant change was observed between 5 and 19 years of age (mean AA = 8.3 D) and between 45 and 60 years of age (mean AA = 0.6 D). AA values as a function of age were best fit by the polynomial regression equation: logAA = 1.93 + 0.49(age) À 0.19(age) 2. Conclusion: Measurements of AA determined using DR are significantly lower than the normative subjective findings published previously. This difference is at least partly due to the depth-of-field of the eye. These norms markedly overestimate accommodative responsivity. DR provides a simple technique for quantifying accommodation in the clinical setting. The normal values for the amplitude of accommodation (AA), i.e., maximum accommodative ability, as a function of age were determined by Donders 1 towards the end of the 19th century and by Duane in the early 20th century. 2 In both cases the subjective push-up (PU) technique was used to measure this parameter. However, several studies have shown that the amplitude findings cited in these classic papers probably overestimated the true result as the authors failed to consider the depth-of-field of the eye, i.e., the dioptric range of object distances over which visual acuity does not deteriorate. 3 Measurements of the maximum accommodative response show a different pattern of change with age compared with the standard clinical measurement of target position when blur is first reported. 4 A recent report by Anderson and Stuebing 5 observed that objective measurements of the AA obtained using an open-field, infra-red optometer in 236 subjects between 3 and 64 years of age were significantly and markedly lower than those found with the subjective PU technique. In some cases, the objectively measured AA was only 56% of that predicted by Hof-ststeter's norms. 6 Le on et al. 7 reported similar findings for a group of 79 subjects between 18 and 30 years of age using dynamic retinoscopy (DR). With this simple technique, the mean AA (7.44 D) was also significantly lower than that found using either the subjective modified push-up (9.84 D) or minus lens (9.43 D) procedures. Dynamic retinoscopy (DR) provides a straightforward method of determining the accommodative response using a...

The DR technique provides a more veridical measurement of the AA because it avoids the overestimation resulting from the depth-of-field. Moreover, the DR technique exhibited higher reproducibility, when compared with subjective methods. These differences may be important when evaluating accommodative dysfunctions or monitoring accommodative therapy. The fact that the DR procedure can be performed using standard clinical equipment makes this a valuable technique both for vision screening programs and routine eye care.

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