title: Optical power of the isolated human crystalline lens.
abstract: OBJECTIVE
  To characterize the age dependence of isolated human crystalline lens power and quantify the contributions of the lens surfaces and refractive index gradient.
  
  
  METHODS
  Experiments were performed on 100 eyes of 73 donors (average 2.8 +/- 1.6 days postmortem) with an age range of 6 to 94 years. Lens power was measured with a modified commercial lensmeter or with an optical system based on the Scheiner principle. The radius of curvature and asphericity of the isolated lens surfaces were measured by shadow photography. For each lens, the contributions of the surfaces and the refractive index gradient to the measured lens power were calculated by using optical ray-tracing software. The age dependency of these refractive powers was assessed.
  
  
  RESULTS
  The total refractive power and surface refractive power both showed a biphasic age dependency. The total power decreased at a rate of -0.41 D/y between ages 6 and 58.1, and increased at a rate of 0.33D/y between ages 58.1 and 82. The surface contribution decreased at a rate of -0.13 D/y between ages 6 and 55.2 and increased at a rate of 0.04 D/y between ages 55.2 and 94. The relative contribution of the surfaces increased by 0.17% per year. The equivalent refractive index also showed a biphasic age dependency with a decrease at a rate of -3.9 x 10(-4) per year from ages 6 to 60.4 followed by a plateau.
  
  
  CONCLUSIONS
  The lens power decreases with age, due mainly to a decrease in the contribution of the gradient. The use of a constant equivalent refractive index value to calculate lens power with the lens maker formula will underestimate the power of young lenses and overestimate the power of older lenses.
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
authors.forename: David
authors.initials: D
authors.lastname: Borja
authors.forename: Fabrice
authors.initials: F
authors.lastname: Manns
authors.forename: Arthur
authors.initials: A
authors.lastname: Ho
authors.forename: Noel
authors.initials: N
authors.lastname: Ziebarth
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Rosen
authors.forename: Rakhi
authors.initials: R
authors.lastname: Jain
authors.forename: Adriana
authors.initials: A
authors.lastname: Amelinckx
authors.forename: Esdras
authors.initials: E
authors.lastname: Arrieta
authors.forename: Robert C
authors.initials: RC
authors.lastname: Augusteyn
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Parel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002648:Child; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D007908:Lens, Crystalline / Q000502:physiology*; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*