The stability of steady state accommodation in human infants

Abstract

Retinal image quality in infants is largely determined by the accuracy and the stability of their accommodative responses. Although the accuracy of infants' accommodation has been investigated previously, little is known about the stability of their responses. We performed two experiments that characterized the stability of infants' steady state accommodation. Analyses were performed in the time domain (root mean square [RMS] deviation) and in the frequency domain (spectral analysis). In Experiment 1, accommodation responses were recorded for a period of 3 s from the left eye of four groups of infants (8-10, 11-13, 14-19, and 20-30 weeks of age) and eight prepresbyopic adults while they focused on a small toy placed at a dioptric viewing distance of 1.0 D (at 1 m). In Experiment 2, accommodation responses were recorded for a period of 14 s from the left eye of a group of 8- to 12-week-old infants and six prepresbyopic adults while they focused on a cartoon image placed at three different dioptric viewing distances (1.25, 2.0, and 3.0 D). The data, collected using a photorefractor sampling at 25 Hz, showed two important characteristics. First, the RMS deviations and the power were quantitatively similar across different infant age groups, and they were significantly larger in infants than in adults. Second, the overall and relative power also increased with the dioptric viewing distance both in infants and adults. At all three dioptric viewing distances, the measures of power were larger in infants than in adults. These data demonstrate that infants' accommodative responses contain instabilities that are qualitatively very similar to those observed in adults. However, the larger RMS deviations suggest that infants are likely to experience larger fluctuations in retinal image quality than adults.

Accommodative Fluctuations, Lens Tension, and Ciliary Body Thickness in Children

“…All accommodative microfluctuation measurements decreased with advancing age in this sample of children. In addition, the mean power values for the high-frequency component (0.005 D 2 /Hz), low-frequency component (0.042 D 2 /Hz), and root mean square (0.49 D) in this study are smaller than those found by Candy and Bharadwaj25 in infants but larger than those found by Day et al12 in young adults. The accommodative ability of children in this study was not yet adult-like but more advanced than the infant state.…”

“…Monocular accommodative response for measurements of microfluctuations was measured using a PowerRefractor (MultiChannelSystems, Reutlingen, Germany) at a sampling rate of 25 Hz and a test distance of 1 m. The instrument has a range of −8.75 to +4.00 D22 and requires a pupil size larger than 3.7 mm 23. Its use has been established for measuring refractive error in children24 and for the measurement of accommodative microfluctuations 11,25. While positioned in a head and chin rest to minimize the head movement, subjects viewed a high-contrast Maltese cross target (angular subtense: 1.4°) at a distance of 0.25 m (−4.00 D) continuously for two, 30-second periods while measurements were taken.…”

Sensitivity of vergence responses of 5- to 10-week-old human infants

“…For vergence, plotted in Figure 4, the mean amplitudes were 0.068 MA for adults and 0.071 MA for infants, which were not significantly different from each other ( t = −0.11, p = 0.54). For accommodation, plotted in Figure 7, the mean amplitudes were 0.05 D for adults and 0.45 D for infants, which were significantly different from each other ( t = 2.76, p = 0.008; Candy & Bharadwaj, 2007). …”

The Effect of Lens-Induced Anisometropia on Accommodation and Vergence during Human Visual Development

“…[41][42][43][44] Subjects were aligned at 1 m from a set of light-emitting diodes (LEDs) immediately beneath a camera aperture. Light from the LEDs passed into the eye and was reflected back from the retina through the pupil.…”

“…The slopes of the functions were determined using linear regression, and these slopes were used to scale each participant's raw data. 32,43,47 The default PR calibration was used for subjects who did not complete that part of the data collection. Calibration slopes of individual subjects are approximately evenly distributed about the default PR calibration slope values, 46 with no strong age-related trends.…”