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Chea-su Kee, Daniel Marzani, Josh Wallman; Differences in Time Course and Visual Requirements of Ocular Responses to Lenses and Diffusers. Invest. Ophthalmol. Vis. Sci. 2001;42(3):575-583.
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purpose. Myopia can be induced in chickens by having them wear either negative
lenses (lens-compensation myopia [LCM]) or diffusers
(form-deprivation myopia [FDM]), whereas positive lenses cause
lens-compensation hyperopia (LCH). These three conditions were compared
with respect to (i) their early time course and (ii) the effect of two
manipulations of the lighting.
methods. Longitudinal changes in ocular dimensions and refractive error were
measured in chicks maintained under three different conditions: (i)
wearing either −15 D lenses or diffusers in a normal light/dark
cycle; (ii) wearing either +15 D lenses, −15 D lenses, or diffusers
with brief periods of stroboscopic lights at the beginning and end of
the dark period; (iii) wearing either +6 D lenses, −6 D lenses, or
diffusers with the nights interrupted by brief periods of white light.
In addition, scleral and choroidal proteoglycan synthesis was measured
in eyes that wore positive lenses, negative lenses, or diffusers for 3
hours followed by different periods of darkness.
results. (i) The time course of the changes in axial length over the first 72
hours was significantly faster in LCM than in FDM. Indeed, the
diffusers did not begin to significantly affect the total length of the
globe for 3 days, although the vitreous chamber had deepened after 9
hours, because the choroid thinned extremely rapidly (within 1 hour)
with either diffusers or negative lenses. (ii) Scleral proteoglycan
synthesis was higher in eyes with negative lenses than in those with
diffusers at 11 hours, but the reverse was true at 27 hours. (iii)
Brief periods of stroboscopic light attenuated FDM more than LCM. (iv)
In contrast, interruption of the nights by brief periods of light
attenuated LCM more than FDM. (v) Neither lighting manipulation
affected LCH. (vi) Choroidal proteoglycan synthesis decreased similarly
with 3 hours of wearing either diffusers or negative lenses.
conclusions. Although both negative lenses and diffusers cause similar increases in
the rate of ocular elongation, the responses differ in time course and
in the effect of manipulations of the daily lighting. The responses to
positive lenses differ from both of these.
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