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Sara J. McCullough, Julie-Anne Little, Kathryn J. Saunders; Optical Quality Measures Of Higher Order Ocular Aberrations And Their Relation To Visual Function In Children With Down Syndrome. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3604. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies report atypical optical structures in Down syndrome (DS) and a degrading influence of the optics on visual performance. Recent work from our laboratory has shown greater levels of higher order ocular aberrations (HOA) and reduced optical quality in children with DS compared with age-matched typically developing children. The present study investigates the relation between measures of optical quality and visual function for children with and without DS.
Participants were 25 children with DS (6-16 years) and 192 age-matched controls. HOA aberrations were measured following cycloplegia for the dominant eye using Shack-Hartmann aberrometry (IRX3, Imagine Eyes). Zernike coefficients were analysed over the central pupil area (3mm diameter, 3rd-6th order) and root mean square (RMS) values of total coma, trefoil, spherical aberration and combined hHOA were calculated. Strehl ratios were derived to describe optical quality. Three measures of visual function were assessed for the dominant eye; high and low contrast recognition acuity and grating resolution acuity. Convolutions of point spread functions (PSF) were also used to simulate image quality.
Weak relations were found between HOA data and all measures of visual function for both the DS and control groups. Statistically significant relations were found between the RMS of coma and low contrast recognition acuity (r=0.14, p<0.05) and grating resolution acuity (r=0.16, p<0.05) for the control group. A similar correlation was found between the RMS of coma and low contrast acuity for the DS group but did not reach statistical significance (r=0.23, p=0.30). Simulated PSF for the DS group were markedly poorer than that of the control group.
Non-rotationally symmetric coma aberrations were more deleterious to visual performance than rotationally symmetric aberrations for both groups. However, in agreement with previous adult studies, no further correlations were found between optical quality and visual performance amongst typically developing children and those with DS. Visual performance remains robust in the presence of HOA which may be explained by neural adaptation which compensates for retinal image blur. Poorer visual acuities in the DS group may suggest this process is compromised by the poor cortical development and atypical cortical organisation reported in DS.
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