title: The effects of simultaneous dual focus lenses on refractive development in infant monkeys.
abstract: OBJECTIVE
  We investigated the effects of two simultaneously imposed, competing focal planes on refractive development in monkeys.
  
  
  METHODS
  Starting at 3 weeks of age and continuing until 150 ± 4 days of age, rhesus monkeys were reared with binocular dual-focus spectacle lenses. The treatment lenses had central 2-mm zones of zero power and concentric annular zones with alternating powers of +3.0 diopter [D] and plano (pL or 0 D) (n = 7; +3D/pL) or -3.0 D and plano (n = 7; -3D/pL). Retinoscopy, keratometry, and A-scan ultrasonography were performed every 2 weeks throughout the treatment period. For comparison purposes data were obtained from monkeys reared with full field (FF) +3.0 (n = 4) or -3.0 D (n = 5) lenses over both eyes and 33 control animals reared with unrestricted vision.
  
  
  RESULTS
  The +3 D/pL lenses slowed eye growth resulting in hyperopic refractive errors that were similar to those produced by FF+3 D lenses (+3 D/pL = +5.25 D, FF +3 D = +4.63 D; P = 0.32), but significantly more hyperopic than those observed in control monkeys (+2.50 D, P = 0.0001). One -3 D/pL monkey developed compensating axial myopia; however, in the other -3 D/pL monkeys refractive development was dominated by the zero-powered portions of the treatment lenses. The refractive errors for the -3 D/pL monkeys were more hyperopic than those in the FF -3 D monkeys (-3 D/pL = +3.13 D, FF -3D = -1.69 D; P = 0.01), but similar to those in control animals (P = 0.15).
  
  
  CONCLUSIONS
  In the monkeys treated with dual-focus lenses, refractive development was dominated by the more anterior (i.e., relatively myopic) image plane. The results indicate that imposing relative myopic defocus over a large proportion of the retina is an effective means for slowing ocular growth.
authors.affiliation: College of Optometry, University of Houston, Texas, United States Vision Cooperative Research Centre, Sydney, Australia.
authors.forename: Baskar
authors.initials: B
authors.lastname: Arumugam
authors.affiliation: College of Optometry, University of Houston, Texas, United States Vision Cooperative Research Centre, 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 State 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: Vision Cooperative Research Centre, Sydney, Australia.
authors.forename: Brien
authors.initials: B
authors.lastname: Holden
authors.affiliation: College of Optometry, University of Houston, Texas, United States Vision Cooperative Research Centre, Sydney, Australia.
authors.forename: Earl L
authors.initials: EL
authors.lastname: Smith
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D018450:Disease Progression; D004867:Equipment Design; D005123:Eye / Q000254:growth & development; D005139:Eyeglasses; D008253:Macaca mulatta; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology* / Q000628:therapy
keywords: Fresnel lenses; emmetropization; eye growth; hyperopia; myopia; refractive error