Abstract
This study quantified preschool children's optical quality in terms of their aberrations and modulation transfer function (MTF), and examined the dependence of MTF on pupil size and grating orientation. Aberrometry was used to measure Zernike coefficients in 34 Chinese preschool children (18 males, 16 females; aged 4.95-6.89 years; mean, 5.91 +/- 0.56). For each subject, after mathematical correction for refractive error, these wavefront errors were used to calculate MTF (lambda = 550 nm) for pupil sizes from 1 to 5 mm and for gratings at orientations in 15 degrees intervals. Aberrations were correlated between right and left eyes, for wavefront RMS and some Zernike coefficients. Average aberrometry results showed that third-order terms predominated, in addition to some positive spherical aberration with an average higher order root mean square (RMS) of 0.20 micro m over a 5-mm pupil. Average MTFs were optimal for 3-mm pupil sizes at lower spatial frequencies (<69 cyc/deg) and slightly better than those found by similar techniques in young adults. Heights of MTFs were significantly related to higher order RMS (Spearman rho = -0.926). MTFs showed a small meridional anisotropy for 3-mm pupils, with average MTF for vertical gratings (horizontal modulation) being slightly, but significantly better than for horizontal gratings (vertical modulation). There was no evidence of an oblique effect in the optics of these children. In these children, ocular optical quality is pupil dependent, shows slight meridional anisotropy and is slightly better than that for young adults.
Highlights
This study quantified preschool children’s optical quality in terms of their aberrations and modulation transfer function (MTF), and examined the dependence of MTF on pupil size and grating orientation
Average MTFs were optimal for 3-mm pupil sizes at lower spatial frequencies (Ͻ69 cyc/deg) and slightly better than those found by similar techniques in young adults
Heights of MTFs were significantly related to higher order root mean square (RMS) (Spearman ϭ Ϫ0.926)
Summary
Aberrometry was used to measure Zernike coefficients in 34 Chinese preschool children (18 males, 16 females; aged 4.95– 6.89 years; mean, 5.91 Ϯ 0.56). Subjects underwent induction of cycloplegia with 3 drops of 1% tropicamide— each drop instilled at 5-minute intervals, because tropicamide has been found to be a suitable cycloplegic agent in this age group.[18] Aberrometry measurements were attempted on the right and left eyes of subjects, approximately 30 minutes after the installation of the last drop (Zywave aberrometer; Bausch & Lomb, Rochester, NY). This is a Hartmann-Shack– based instrument[19] that samples the pupil at 0.6-mm intervals. Aberration measurements could not be obtained from the left eye of one subject (a girl aged 5.6 years), because she had poor tear quality, and results for this (left) eye were excluded from analysis, but aberration measurements were obtained from the right eyes of all subjects
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