title: Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens.
abstract: OBJECTIVE
  To determine whether the cellular physiology of the lens actively maintains the optical properties of the lens and whether inhibition of lens transport affects overall visual quality.
  
  
  METHODS
  One lens from a pair of bovine lenses was cultured in artificial aqueous humor (AAH), while the other was cultured in either AAH-High-K+ or AAH + 0.1 mM ouabain for 4 hours. Lens pairs or whole enucleated eyes were then imaged in 4.7 Tesla (T) high-field small animal magnet. Lens surface curvatures, T1 measurements of water content, and T2 measurements of water/protein ratios were extracted from cultured lenses, while the geometrical parameters that define the optical pathway were obtained from whole eyes. Gradients of refractive index (GRIN), calculated from T2 measurements, and the extracted geometric parameters were inputted into optical models of the isolated lens and the whole bovine eye.
  
  
  RESULTS
  Inhibiting circulating fluxes by inhibiting the Na/K-ATPase with ouabain or depolarization of the lens potential by High K+ caused changes to lens water content, the water/protein ratio (GRIN) and surface geometry that manifested as an increase in optical power and a decrease in negative spherical aberration in cultured lenses. Changes to optical properties of the lens resulted in a myopic shift that impaired vision quality in the optical model of the bovine eye.
  
  
  CONCLUSIONS
  The cellular physiology of the lens actively maintains its optical properties and inhibiting the Na/K/ATPase induces a myopic shift in vision similar to that observed clinically in patients who go on to develop cataract.
authors.affiliation: School of Optometry and Vision Science School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Aukland, New Zealand 2Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Vaghefi
authors.affiliation: School of Optometry and Vision Science School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Aukland, New Zealand.
authors.forename: Andy
authors.initials: A
authors.lastname: Kim
authors.affiliation: School of Optometry and Vision Science School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Aukland, New Zealand 2Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand 3Department of Physiology, S.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Donaldson
mesh_terms: D000818:Animals; D002417:Cattle; D007908:Lens, Crystalline / Q000033:anatomy & histology* / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008954:Models, Biological; D012029:Refraction, Ocular / Q000502:physiology*