Abstract
Purpose :
Early visual experience can modulate postnatal ocular growth. We recently reported the role of astigmatic blur in myopia development by comparing the effects of -10D hyperopic defocus with and without astigmatic blur on chicks. Here we investigated whether astigmatic blurs can affect the development and recovery of moderate myopia, induced by spherical and sphero-cylindrical lenses having an identical spherical-equivalent hyperopic defocus (-5D)
Methods :
Five-day old White Leghorn chicks (Gallus Gallus Domesticus,n=26) were randomly assigned to wear one of three lenses monocularly for a week (P5-P12): (1) spherical lens (-5D, Hyperopic defocus, “H”;n=8); (2) sphero-cylindrical lens with vertical axis; (-1.00DS/-8.00DC x 90; Hyperopic With-The-Rule astigmatic defocus, “H-WTR”; n = 9); or (3) sphero-cylindrical lens-wear with horizontal axis; -1.00DS/-8.00DC x 180, Hyperopic Against-The-Rule astigmatic defocus, “H-ATR”; n = 9). All three lenses imposed the same degree of -5D spherical-equivalent (SE) hyperopic error. Refractive state and ocular axial dimensions were measured using a modified Hartinger refractometer and a high-resolution A-scan ultrasonographer, respectively, at the end of the lens-wear period (P12) and after the lens removal (P15 and P19). A mixed-model two-way ANOVA with Bonferroni’s pairwise post hoc comparisons was used for statistical analysis. All parameters were expressed as the interocular difference (treated eye – fellow untreated eye; mean±SD)
Results :
Compared to the -5D spherical lens, both sphero-cylindrical lenses induced significantly less myopia (H= -4.20±0.29D; H-WTR= -0.55±0.27D; H-ATR= -2.65±0.29D;both p<0.001) but higher refractive astigmatism (H= -0.22±0.26D; H-WTR= -3.54±0.24D; H-ATR= -2.36±0.26D;both p<0.001) at the end of the one-week treatment period. Compared to H-ATR, H-WTR induced less myopia (p<0.001), higher refractive astigmatism (p<0.001), and shallower anterior chamber depth (p<0.01). After 3 days of recovery, no significant difference in SE was found between H-WTR and H-ATR (H-WTR= -0.59±0.29D vs H-ATR= +0.46±0.30D,p=0.056), but H-WTR had significantly shallower anterior chamber depth (p=0.003) and thicker lens (p=0.04) when compared to H-ATR. After 1 week of recovery, no significant differences in any parameter were found across the three groups
Conclusions :
The orientation of the astigmatic blur can modulate myopic-astigmatic eye growth and its recovery
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.