Abstract
Purpose :
Simultaneous peripheral myopic (positive) defocus can reduce the axial length and increase choroidal thickness. However, the effect of simultaneous negative defocus on ocular biometrics in humans is unknown. We investigated the effect of simultaneous negative (-5.0/plano), and positive defocus (+5.0/plano) on human axial length (AL) and choroidal thickness (CT).
Methods :
Fourteen myopic subjects aged 18-30 years with spherical equivalent -0.75 to -5.00D were enrolled in a short-term (60 mins), cross-over, investigator-masked trial. Subjects used soft contact lenses for refractive correction and wore 4 experimental and 2 control spectacle lenses (Conventional single vision plano lens & MiYOSMART) mounted on a spectacle frame in their right eye and conventional plano lens in their left eye on 6 different days with a 24-hour washout period between lens wear. Experimental lenses had a plano central zone of 9 or 2 mm with concentric alternating zones of either plano and +5.0 D (+5.0/Pl 9 mm & +5.0/Pl 2mm) or plano and -5.0 D ( -5.0/Pl 9 mm & -5.0/Pl 2mm). AL was measured using the Lenstar LS 900® (Haag Streit, Switzerland) and CT was measured using the ETDRS grid, DRI OCT Triton™ (Topcon). The post-lens wear change in AL (Δ AL) and average CT were calculated, and data was analyzed using repeated measures ANOVA.
Results :
Overall, shorter AL was observed with experimental lenses compared to the plano lens in the test eye (-06±13 µm vs 02±12 µm, p=0.004). However, no significant reduction was observed in the contralateral eye (-06±14 µm vs -05±17 µm, p=0.86). With MiYOSMART, AL reduction in the test and contralateral eyes was not significant (p>0.19). The decrease in AL was not different between -5.0/Pl & +5.0/Pl (p=0.88) and between the central clear zone 9 mm & 2 mm (p=0.46). Change in CT with experimental lenses was not different from the baseline in both test and contralateral eyes.
Conclusions :
In this study, short-term exposure to simultaneous negative defocus induced a significantly shorter axial length.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.