Accommodative accuracy by retinoscopy versus autorefraction spherical equivalent or horizontal meridian power.

BACKGROUND: To assess agreement between accommodative lag by monocular estimation method (MEM) retinoscopy and Nott retinoscopy compared to open-field autorefraction using spherical equivalent versus power in the 180 meridian for both children and adults.

METHODS: Twenty-six children aged 7-16 years (mean: 9.9 ± 2.3) and 27 adults aged 22-29 years (mean: 24.2 ± 1.7) participated. Accommodative lag was measured by examiners with autorefraction and separate examiners using MEM and Nott retinoscopy while subjects viewed 6/18 letters at 33 cm. Five measures of autorefraction were averaged with vector analysis and both power in the 180 meridian and spherical equivalent was determined. Two-factor repeated measures analysis of variance and the mean difference and 95 per cent limits of agreement were calculated.

RESULTS: Mean (standard deviation) lag for each technique was: MEM = 0.69 (0.52) D, Nott = 0.62 (0.51) D, autorefraction in 180 = 0.66 (0.50) D and autorefraction spherical equivalent = 0.60 (0.46) D. Lag did not vary across techniques (p = 0.48), but children did have smaller lags than adults (p < 0.001) and greater amounts of uncorrected astigmatism (0.61 ± 0.09 D versus 0.42 ± 0.08 D, p = 0.02). There was no significant interaction between age group and technique (p = 0.74). Mean differences between techniques were small, ranging from -0.14 to +0.06 D. Ninety-five per cent limits of agreement ranged from ±0.80 to ±1.33 around the mean with the narrowest ranges found for comparisons made to autorefraction in 180. Limits of agreement were also narrowest in children as compared to adults with similar mean differences between age groups.

CONCLUSIONS: This study demonstrates the mean agreement between autorefraction and retinoscopic techniques is centred on zero (no bias) in both children and adults. The range of agreement becomes narrower when autorefraction power in the 180 is calculated, even for a sample of subjects with moderately small amounts of uncorrected astigmatism.