title: The Effects of the Relative Strength of Simultaneous Competing Defocus Signals on Emmetropization in Infant Rhesus Monkeys.
abstract: We investigated how the relative surface area devoted to the more positive-powered component in dual-focus lenses influences emmetropization in rhesus monkeys.
  
  
  
  From 3 to 21 weeks of age, macaques were reared with binocular dual-focus spectacles. The treatment lenses had central 2-mm zones of zero-power and concentric annular zones that had alternating powers of either +3.0 diopters (D) and 0 D (+3 D/pL) or -3.0 D and 0 D (-3 D/pL). The relative widths of the powered and plano zones varied from 50:50 to 18:82 between treatment groups. Refractive status, corneal curvature, and axial dimensions were assessed biweekly throughout the lens-rearing period. Comparison data were obtained from monkeys reared with binocular full-field single-vision lenses (FF+3D, n = 6; FF-3D, n = 10) and from 35 normal controls.
  
  
  
  The median refractive errors for all of the +3 D/pL lens groups were similar to that for the FF+3D group (+4.63 D versus +4.31 D to +5.25 D; P = 0.18-0.96), but significantly more hyperopic than that for controls (+2.44 D; P = 0.0002-0.003). In the -3 D/pL monkeys, refractive development was dominated by the zero-powered portions of the treatment lenses; the -3 D/pL animals (+2.94 D to +3.13 D) were more hyperopic than the FF-3D monkeys (-0.78 D; P = 0.004-0.006), but similar to controls (+2.44 D; P = 0.14-0.22).
  
  
  
  The results demonstrate that even when the more positive-powered zones make up only one-fifth of a dual-focus lens' surface area, refractive development is still dominated by relative myopic defocus. Overall, the results emphasize that myopic defocus distributed across the visual field evokes strong signals to slow eye growth in primates.
authors.affiliation: College of Optometry, University of Houston, Texas, United States 2Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Baskar
authors.initials: B
authors.lastname: Arumugam
authors.affiliation: College of Optometry, University of Houston, Texas, United States 2Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Li-Fang
authors.initials: LF
authors.lastname: Hung
authors.affiliation: Center for Myopia Research, School of Optometry, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 4State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat Sen University, Guangzhou, People's Republic of China.
authors.forename: Chi-Ho
authors.initials: CH
authors.lastname: To
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Padmaja
authors.initials: P
authors.lastname: Sankaridurg
authors.affiliation: College of Optometry, University of Houston, Texas, United States 2Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Earl L
authors.initials: EL
authors.lastname: Smith
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D005123:Eye / Q000254:growth & development*; D005139:Eyeglasses; D007908:Lens, Crystalline / Q000254:growth & development; D008253:Macaca mulatta; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology / Q000628:therapy*; D042262:Retinoscopy