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E. A. DeHoog, C. E. Clifford-Donaldson, E. M. Harvey, J. M. Miller, V. Dobson, J. Schwiegerling; Astigmatism and Higher-Order Aberrations Measured With a Handheld Aberrometer in Native American Children. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1426. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare astigmatism measurement with a custom handheld aberrometer and the Retinomax autorefractor, as well as evaluate higher order aberrations in preschoolers with a high prevalence of astigmatism.
Cycloplegic cylinder error was measured in a sample of 15 Native American preschoolers, aged 3.3 to 5.1 years, using a portable Shack Hartmann aberrometer, (PeWE). The results obtained by the PeWE were compared with cycloplegic Retinomax autorefractometer (Nikon, Melville, NY) measurements. For each child, repeated measures from the PeWE were used to calculate J0 and J45 crossed cylinder terms and averaged to give a single mean J0 and mean J45 for each child. These mean values were compared to the cylinder refraction obtained with the Retinomax converted to J0 and J45. Bland Altmann plots were calculated to determine the bias and variability between the two devices. Wavefronts obtained with the PeWE were reconstructed and the magnitude of spherical aberration and coma was determined.
Bland Altmann plots showed 0.5 D and 0.25 D bias between the Retinomax Autorefractometer and the PeWE for J0 and J45, respectively. The PeWe gives a lower magnitude of cylinder than the Retinomax. There also appeared to be a systematic increase in the difference between the two devices as cylinder error increased, with the PeWE giving progressively lower levels of cylinder at higher errors. The average level of spherical aberration for a 5.7 mm pupil was 0.00 ± 0.25 microns. The average magnitude of coma was 0.49 ± 0.32 microns.
We were able to obtain both PeWE and Retinamox measurements for all 15 children. There is a strong correlation between the J0 values for the PeWE and the Retinomax, with r2 = 0.84 (p<0.001). The correlation between the J45 terms, however, was much lower (r2 = 0.35, not significant). The low correlation for J45 is likely due to the low prevalence of obliquely oriented astigmatism in our sample. There exists a bias between the two devices and a systematic change with increased magnitude of cylinder error. One possible explanation for the differences between Retinomax and PeWE results could be the size of the pupil over which the two devices operate. In this study we examined cycloplegic refractions, so wavefronts were measured over large diameter pupils. Presence of higher order aberrations can affect the refraction predicted by the wavefront sensor. Moving forward, we will analyze the effect of pupil diameter on the PeWe measurements to determine which pupil size gives the best correlation with the Retinomax.
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