| PurposeTo investigate whether bifocal lenses treatment interrupted by single vision lenses for a short period of time could reach a compatible effect of bifocal lenses treatment continuously on lens-induced myopia.To evaluate the effect of bifocal lenses combined with atropine on lens-induced myopia in chicks.To investigate the effects of retinal defocus and image degradation on emmetropization in chicks.Methods1.Nine-day old chicks were fitted monocularly with-10 Diopter(D)lenses for 3 days to induce myopia.Then chicks were randomly assigned to one of five treatment groups for the following 6 days.Group 1: wore-10/-5 D bifocal lenses for 12 hours;Group 2: wore-10/-5 D lenses for 10 hours and-10 D SV lenses for 2 hours per day in the lighting hours;Group 3: wore-10/-5 D lenses for 8 hours and-10 D SV lenses for 4 hours;Group 4: wore-10/-5 D lenses for 6 hours and-10 D SV lenses for 6 hours;Group 5: wore-10 D SV lenses for 12 hours.Refractive error and biometry measurements were done at the ages of 9,12,15 and 18.2.Nine-day old chicks were fitted monocularly with-10 Diopter(D)lenses for 3 days to induce myopia.Then chicks were randomly assigned to one of four treatment groups.Group 1:-10 D SV lenses & PBS;Group 2:-10 D SV lenses & atropine;Group 3:-10/-5 D lenses & PBS;Group 4:-10/-5 D lenses & atropine.Refractive error and biometry measurements were done at the ages of 9,12,15 and 18.3.Each of 4 Bangerter diffusing filters 0.6,0.1,<0.1,and 0.0 combined with either +10D or-10 D lenses were fitted monocularly to 14-day-old chicks.Axial ocular dimensions and refractive errors were monitored after 2 hours,2,4 and 6 days.Results1.Mopic shifts in refractive errors were seen in all groups after 3 days(-9.19±2.23 D,-9.13±2.22 D,-8.89±1.18 D,-8.91±1.61 D and-9.05±2.07 D,respectively),accompanied with increases in axial length.The myopic shifts were significantly corralted with the changes in axial length(P<0.001).Hyperopic shifts were shown in all groups with bifocal lenses treatment(P<0.001).However,at the age of 18,group 4 exhibited more myopic refraction than group 1 and greater changes in choroidal thickness than group 5(P<0.05).2.Over the 6-day treatment period,chicks in groups 2,3 and 4 showed less myopic changes in terms of refractive errors and axial length compared with group 1(P<0.05).The hyperopic shifts were 2.50±1.34D(P<0.01)and 0.29±0.77D(P>0.05)in group 3,and 1.92±1.72 D and 1.61±1.17 D in group 5(P<0.05),both of which were greater than group 2(P<0.05).In group 4,the chororidal thickness increased dramatically and the increase was greater than other groups(P<0.01),and the inner eye length increased to 0.210±0.140 mm at aged 15 and decreased to 0.014±0.158 mm by the end.3.The <0.1 and 0.0 filters induced significant form deprivation myopia in +10D lenses group;the 0.6 and 0.1 filters induced less hyperopic shifts in refractive error,coupled to significant increases in both vitreous chamber depths and optical axial lengths as in +10D alone group.All the treatments in-10 D lenses showed large and similar myopic shifts(p<0.05).Conclusions1.Daily four hours of single vision lenses wear will not affect the anti-myopia effect of bifocal lenses.2.The anti-myopia effect could be enhanced after combining bifocal lenses and atropine treatments.3.Severe image degradation could disrupt retina from responding to the defocus,and induce form deprivation myopia. |
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