Anomalous Wavefront Aberrations Reduce Optical Quality In Down Syndrome

Purpose:Down syndrome (DS) is associated with ocular abnormalities and reduced visual function. Structural and functional differences in the optics of DS eyes are reported in the literature. Studies report a thinner, steeper cornea and a thinner crystalline lens and, functionally, a degrading influence of DS optics on resolution acuity. The present study further investigates optical quality in DS by comparing wavefront aberrations in DS and control eyes. Methods: Participants were 38 children with DS (6-16 years) and 209 age-matched controls. Monochromatic higher order aberrations (HOAs) were measured following cycloplegia (1% Cyclopentolate) using Shack-Hartmann aberrometry (IRX3, Imagine Eyes). HOAs were analysed over a fixed 5mm pupil using Zernike polynomials from 3rd to 6th order. Optical quality was assessed using the Strehl ratio (calculated by the IRX3 software) over 3, 4 and 5mm pupil diameters. Results: HOAs were measured successfully from 73% of the DS group and 97% of controls. Right eye data were analysed. Mean root mean square of total HOAs differed significantly between groups (0.33µm±0.09 DS; 0.29µm±0.12 controls) (Mann Whitney z=-2.34, p=0.02). Mean spherical equivalent did not correlate significantly with the degree of HOAs in either DS or control groups ( p>0.05). Significant differences were found between the DS and control group for trefoil sine term Z(3,-3), horizontal coma Z(3,1), spherical aberration Z(4,0), quadrafoil cosine term Z(4,4), Z(5,-3), Z(5,-1), Z(5,1) and Z(6,4). The wavefront patterns produced a significantly lower Strehl ratio in the DS group compared to controls over all pupil diameters with the greatest difference seen at 3mm (0.27±0.14 DS; 0.43±0.16 controls) (Mann Whitney z=4.84, p