title: Temporal properties of compensation for positive and negative spectacle lenses in chicks.
abstract: OBJECTIVE
  Chicks' eyes rapidly compensate for defocus imposed by spectacle lenses by changing their rate of elongation and their choroidal thickness. Compensation may involve internal emmetropization signals that rise and become saturated during episodes of lens wear and decline between episodes. The time constants of these signals were measured indirectly by measuring the magnitude of lens compensation in refractive error and ocular dimensions as a function of the duration of episodes and the intervals between the episodes.
  
  
  METHODS
  First, in a study of how quickly the signals rose, chicks were subjected to episodes of lens-wear of various durations (darkness otherwise), and the duration required to cause a half-maximum effect (rise-time) was estimated. Second, in a study of how quickly the signals declined, various dark intervals were imposed between episodes of lens-wear, and the interval required to reduce the maximum effect by half (fall-time) was estimated.
  
  
  RESULTS
  The rise-times for the rate of ocular elongation and choroidal thickness were approximately 3 minutes for positive and negative lenses. The fall-times had a broad range of time courses: Positive lenses caused an enduring inhibition of ocular elongation with a fall-time of 24 hours. In contrast, negative lenses caused a transient stimulation of ocular elongation with a fall-time of 0.4 hour.
  
  
  CONCLUSIONS
  The effects of episodes of defocus rise rapidly with episode duration to an asymptote and decline between episodes, with the time course depending strongly on the sign of defocus and the ocular component. The complex etiology of human myopia may reflect these temporal properties.
authors.affiliation: Department of Biology, The City College of The City University of New York, New York 10031, USA. xiaoying@sci.ccny.cuny.edu
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Zhu
authors.forename: Josh
authors.initials: J
authors.lastname: Wallman
mesh_terms: D000818:Animals; D002645:Chickens; D002829:Choroid / Q000503:physiopathology; D003261:Contact Lenses; D003623:Dark Adaptation; D004195:Disease Models, Animal; D005123:Eye / Q000000981:diagnostic imaging / Q000254:growth & development*; D006956:Hyperopia / Q000209:etiology / Q000503:physiopathology*; D009216:Myopia / Q000209:etiology / Q000503:physiopathology*; D012590:Sclera / Q000503:physiopathology; D012683:Sensory Deprivation; D013997:Time Factors; D014463:Ultrasonography
references.citation: Vision Res. 1995 Jan;35(1):37-50
references.pmid: 7839608
references.citation: J Am Optom Assoc. 1995 Jul;66(7):405-14
references.pmid: 7560727
references.citation: Vision Res. 2004 Mar;44(7):643-53
references.pmid: 14751549
references.citation: Exp Eye Res. 2000 Apr;70(4):519-27
references.pmid: 10866000
references.citation: Vision Res. 2008 Sep;48(19):1980-91
references.pmid: 18585403
references.citation: Invest Ophthalmol Vis Sci. 2006 Nov;47(11):4687-99
references.pmid: 17065475
references.citation: Vision Res. 1987;27(7):1139-63
references.pmid: 3660666
references.citation: Epidemiol Rev. 1996;18(2):175-87
references.pmid: 9021311
references.citation: Vision Res. 1995 May;35(9):1175-94
references.pmid: 7610579
references.citation: Ann Acad Med Singap. 2004 Jan;33(1):7-15
references.pmid: 15008555
references.citation: Vision Res. 1988;28(5):639-57
references.pmid: 3195068
references.citation: Exp Eye Res. 2006 Aug;83(2):456-64
references.pmid: 16635488
references.citation: Ophthalmic Physiol Opt. 1992 Oct;12(4):448-56
references.pmid: 1293533
references.citation: Invest Ophthalmol Vis Sci. 2002 Feb;43(2):291-9
references.pmid: 11818369
references.citation: Vision Res. 2001 Feb;41(3):267-73
references.pmid: 11164443
references.citation: Invest Ophthalmol Vis Sci. 1993 Mar;34(3):690-4
references.pmid: 8449687
references.citation: Neuron. 2004 Aug 19;43(4):447-68
references.pmid: 15312645
references.citation: J Vis. 2008 Mar 03;8(3):1.1-12
references.pmid: 18484807
references.citation: Br J Ophthalmol. 2001 Jul;85(7):855-60
references.pmid: 11423462
references.citation: Vision Res. 2002 Nov;42(24):2651-68
references.pmid: 12445851
references.citation: Invest Ophthalmol Vis Sci. 2000 May;41(6):1249-58
references.pmid: 10798638
references.citation: Optom Vis Sci. 1999 May;76(5):308-15
references.pmid: 10375247
references.citation: Exp Eye Res. 2001 Oct;73(4):533-46
references.pmid: 11825024
references.citation: Invest Ophthalmol Vis Sci. 2005 Jul;46(7):2238-41
references.pmid: 15980206
references.citation: Invest Ophthalmol Vis Sci. 2003 Jul;44(7):2818-27
references.pmid: 12824218
references.citation: Invest Ophthalmol Vis Sci. 2000 May;41(6):1259-69
references.pmid: 10798639
references.citation: Invest Ophthalmol Vis Sci. 2000 Jun;41(7):1623-8
references.pmid: 10845578
references.citation: Vision Res. 1998 Nov;38(22):3505-15
references.pmid: 9893785
references.citation: Vision Res. 2006 Jan;46(1-2):267-83
references.pmid: 16139323
references.citation: J Comp Physiol A. 1996 Dec;179(6):837-42
references.pmid: 8956500
references.citation: Vision Res. 1997 Jun;37(12):1557-64
references.pmid: 9231222
references.citation: Exp Eye Res. 1998 Feb;66(2):163-81
references.pmid: 9533843
references.citation: Ophthalmic Physiol Opt. 1999 Mar;19(2):103-11
references.pmid: 10615446
references.citation: Vision Res. 1995 May;35(9):1337-44
references.pmid: 7610595
references.citation: Invest Ophthalmol Vis Sci. 2007 Mar;48(3):957-62
references.pmid: 17325132
references.citation: Optom Vis Sci. 1995 Jul;72(7):506-10
references.pmid: 8539015
references.citation: Ophthalmic Physiol Opt. 1997 Jul;17(4):279-90
references.pmid: 9390372
references.citation: Vision Res. 1996 Apr;36(7):1023-36
references.pmid: 8736261
references.citation: Vision Res. 2003 Jun;43(14):1519-31
references.pmid: 12782066
references.citation: Invest Ophthalmol Vis Sci. 1980 Oct;19(10):1250-5
references.pmid: 7419376
references.citation: Invest Ophthalmol Vis Sci. 2002 Feb;43(2):332-9
references.pmid: 11818374
references.citation: Invest Ophthalmol Vis Sci. 2002 Dec;43(12):3633-40
references.pmid: 12454029
references.citation: Acta Ophthalmol Scand. 1996 Jun;74(3):213-9
references.pmid: 8828713
references.citation: Nat Med. 1995 Aug;1(8):761-5
references.pmid: 7585177
references.citation: Vision Res. 2005 Jun;45(13):1667-77
references.pmid: 15792842
references.citation: Optom Vis Sci. 2000 Sep;77(9):465-72
references.pmid: 11014673