SIGNIFICANCE The prevalence of myopia and use of electronic displays by children has grown rapidly in recent years. We found that children viewing electronic displays, however, experience hyperopic defocus levels similar to those previously reported for other stimuli. PURPOSE This study aimed to compare accommodative behavior of nonmyopic and myopic children viewing a computer screen or mobile phone. METHODS Accommodative behavior was examined in 11 nonmyopic and 8 myopic children (11.32 ± 2.90 and 14.13 ± 2.30 years, respectively; P = .04; refractions, +0.51 ± 0.51 and −2.54 ± 1.29, respectively) using an open-field autorefractor (Grand Seiko) at target vergences from −0.25 to −5.95 D. Different size (scaled or nonscaled) and type (text or movie) stimuli were presented on an LCD monitor (distant) or an iPhone (near), with subjects viewing monocularly or binocularly in an illuminated or dark room. RESULTS At the typical reading distances (16.8 and 29.8 cm), all 19 children exhibited some amount of accommodative lag. Stimulus type had little impact on accommodation. However, slightly but statistically significant lower slopes were observed (Bonferroni-corrected significance level of P ≤ .01) for low room lighting (0.80 vs. 0.76; t test, t = 3.88; P = .003), nonscaled targets (0.83 vs. 0.77; t test, t = 4.28; P = .001), and monocular viewing (0.83 vs. 0.74; t test, t = 4.0; P = .002) in the nonmyopic group only. When viewing nonscaled stimuli binocularly (natural viewing), the means and standard deviations of accommodative lags (averaged across room lights on and off, and text and movie) were generally larger for the nonmyopes at all distances and were largest at 16.8 cm (1.31 ± 0.32 D for the nonmyopes and 1.11 ± 0.35 for the myopes; t test, t = 2.62; P = .01). CONCLUSIONS Generally small (mostly <1.00 D) amounts of hyperopic defocus are present in children binocularly viewing handheld electronic devices (nonmyopes slightly more than myopes). Modern electronic devices do not expose children to unusually high levels of hyperopic defocus.

SIGNIFICANCE Measurement of ocular aberrations is a critical component of many optical corrections. PURPOSE This study examines the accuracy and repeatability of a newly available high-resolution pyramidal wavefront sensor–based aberrometer (Osiris by Costruzione Strumenti Oftalmici, Firenze, Italy). METHODS An engineered model eye and a dilated presbyopic eye were used to assess accuracy and repeatability of aberration measurements after systematic introduction of lower- and higher-order aberrations with calibrated trial lenses (sphere +10.00 to −10.00 D, and astigmatic −4.00 and −2.00 D with axis 180, 90, and 45°) and phase plates (−0.57 to 0.60 μm of Seidel spherical aberration defined over a 6-mm pupil diameter). Osiris aberration measurements were compared with those acquired on a previously calibrated COAS-HD aberrometer for foveal and peripheral optics both with and without multizone dual-focus contact lenses. The impact of simulated axial and lateral misalignment was evaluated. RESULTS Root-mean-square errors for paraxial sphere (corneal plane), cylinder, and axis were, respectively, 0.07, 0.11 D, and 1.8° for the engineered model and 0.15, 0.26 D, and 2.7° for the presbyopic eye. Repeatability estimates (i.e., standard deviation of 10 repeat measures) for the model and presbyopic eyes were 0.026 and 0.039 D for spherical error. Root-mean-square errors of 0.01 and 0.02 μm, respectively, were observed for primary spherical aberration and horizontal coma (model eye). Foveal and peripheral measures of higher- and lower-order aberrations measured with the Osiris closely matched parallel data collected with the COAS-HD aberrometer both with and without dual-focus zonal bifocal contact lenses. Operator errors of focus and alignment introduced changes of 0.018 and 0.02 D/mm in sphere estimates. CONCLUSIONS The newly available clinical pyramidal aberrometer provided accurate and repeatable measures of lower- and higher-order aberrations, even in the challenging but clinically important cases of peripheral retina and multifocal optics.

PurposeThe PowerRef 3 is frequently used in studying the near triad of accommodation, vergence and pupil responses in normal and clinical populations. Within a range, the defocus measurement of the PowerRef 3 is linearly related to the eye's defocus. While the default factory‐calibrated slope of this relation (calibration factor) is 1, it has been shown that the slope can vary across individuals. Here, we addressed the impact of changes in viewing distance, age and defocus of the eye on the calibration factor.MethodsWe manipulated viewing distance (40 cm, 1 m and 6 m) and recruited participants with a range of accommodative capabilities: participants in their 20s, 40s and over 60 years old. To test whether any effect was larger than the range of measurement reliability of the instrument, we collected data for each condition four times: two in the same session, another on the same day, and one on a different day.ResultsThe results demonstrated that viewing distance did not affect the calibration factor over the linear range, regardless of age or uncorrected refractive error. The largest proportion of the variance was explained by between‐subject differences.ConclusionsCalibration data for the PowerRef 3 were not sensitive to changes in viewing distance. Nevertheless, our results re‐emphasise the relevance of calibration for studies of individual participants.

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