A comparison of the reliability of dynamic retinoscopy and subjective measurements of amplitude of accommodation

Abstract

Dynamic retinoscopy (DR) is an objective technique for assessing maximum accommodative responsivity. The present study examined the test-retest reliability of this procedure when measuring the amplitude of accommodation (AA). In the first trial, the within-session repeatability of the AA was measured in 79 subjects between 18 and 30 years of age using DR and two subjective procedures, namely the modified push-down (MPD) and minus lens (ML) techniques. Data were collected by two different examiners. In a second trial, the inter-session repeatability of the AA was assessed in 76 subjects by a single evaluator with a time interval of 7 days between the first and second sessions. The repeatability, reproducibility and agreement between the methods were determined using the mean difference, 95% limits of agreement, intraclass correlation coefficient and concordance correlation coefficient. DR showed the lowest mean value of AA in each trial (average for the two trials = 7.44 D) while the equivalent mean values for the MPD and ML techniques were 9.84 and 9.43 D, respectively. Further, DR showed the best repeatability in both the repeatability trials and poorer inter-examiner agreement was observed for the MPD and ML procedures. The concordance correlation coefficient for DR-MPD, DR-ML and MPD-ML procedures were 0.32, 0.33 and 0.62, respectively for the within-session trial and 0.31, 0.36 and 0.76, respectively for the inter-session trial. 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.