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SJ Judge, JR Phillips; Form Deprivation Myopia in Infancy is Associated With Permanent Changes in the Mechanical Properties of Sclera in the New World Monkey Callithrix Jacchus . Invest. Ophthalmol. Vis. Sci. 2002;43(13):184.
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Purpose: To investigate the long term effect of form deprivation myopia early in life on the mechanical properties of sclera late in life of the same animals. Methods: Two groups of animals were studied: an older group, in which form deprivation myopia had been induced in one eye early in life by lid-suture for <5 weeks, after which the lids were re-opened and another group consisting of normal young animals. Posterior scleral strips, 3.25 mm wide and 200-230 microns thick (measured with a micrometer) were cut from each eye of each animal, shortly after death by barbiturate overdose. Each strip was mounted in a precision stretching device in a chamber held at 37ºC. The test length of each strip was 6 mm. An ascending sequence of isotonic loads was applied covering the range associated with normal intraocular pressure (IOP). The time-course of extension was recorded (2 samples/s) for 20 mins at each load. After unloading a recovery period of 20 mins was allowed before the next load was applied. View OriginalDownload SlideView OriginalDownload Slide Results: Strain and compliance of scleral strips from eyes of older animals, at a load of 1.5g (equivalent to an IOP of approximately 15 mm Hg) are plotted in the figure. Compliance is computed as the slope of the strain v. load function, at a load of 1.5g. Each eye is represented by a dipole linking the compliance and strain values measured at 10s with those measured at 1000s after load application. The dipole indicates the nature of creep. Symbol shapes identify animals. Sclera from eyes which had been lid-sutured and had developed form deprivation myopia more than 10 yrs earlier (filled symbols) was more compliant than that of fellow eyes (open symbols). Two eyes remained myopic at the time of the experiment. At low loads (corresponding to lower than normal IOP) sclera from normal young animals (not shown) was more compliant than that of older animals. Conclusion: Monocular deprivation early in life causes long-lasting changes in the mechanical properties of sclera.
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