Abstract
Purpose: :
To determine the distribution and characteristics of off-axis higher order aberrations (HOAs) in the eyes of myopic and non-myopic children.
Methods: :
On and off-axis (30° temporal, nasal and inferior retinal fields) cycloplegic refractive error (RE) and HOAs were obtained with a Shack-Hartmann aberrometer from right eyes of children participating in the Sydney Myopia Study. Analyses were performed on a sample of high school children (year 7, mostly aged 12 years old). Myopia was defined as M≤-0.50D. Eyes with astigmatism >1.00D and PD<5mm were excluded from analysis. Off-axis HOAs (3rd and 4th orders) and RMS values were analysed. Comparisons between samples were conducted using Univariate-adjusted analysis of variance with significance set at p<0.05.
Results: :
A total of 1,603 children (164 myopes; 442 emmetropes; 997 hyperopes) were analysed. Mean on-axis M of RE groups was -1.91 ± 1.38D (myopes), -0.05 ± 0.58D (emmetropes), and 1.10 ± 0.68D (hyperopes). On average, off-axis coma RMS and 3rd orders RMS were 2 times higher than on-axis mean values for all RE groups. Low myopes had significantly higher levels of coma, 3rd orders RMS and HO RMS (3rd to 6th orders) than emmetropes (p<0.05) and hyperopes (p<0.05) in the temporal field. Fourth orders RMS did not increase with eccentricity. Hyperopic eyes had higher levels of off-axis spherical aberration (SA) and 4th orders RMS than emmetropic and myopic eyes but the differences were not always statistically significant.
Conclusions: :
Similar to on-axis aberrations and to previous reports of off-axis HO aberrations in adults, there were no significant differences in the mean levels of off-axis HOAs between RE groups. Myopic eyes had higher HO RMS only temporally. Although HOAs increased in the peripheral retina, their magnitude was small in comparison to lower order aberrations to have a major effect in reducing the optical quality of the peripheral retina.
Keywords: refractive error development • aberrations • myopia