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Objective To observe the axial length,refractive error and the pathology changes of guinea pigs in short-term form deprivation myopia(ST-FDM).Explore the peculiarity and pathogenesis of the ST-FDM.Methods 50 four weeks of age guinea pigs were randomly divided into normally group(25) and form deprivation group(25).The last group is divided into five sub-group(deprived 1 days,deprived 4 days,deprived 7 days,deprived 14 days,deprived 21 days).Right eyes of the experimental groups were covered a translucent plastic occluder,the left eyes were opened.Refraction,axial lenth,stmcture and ultrastructure of sclera were measured respectively before the experimental and after 1,4,7,14,21days.Results The axial length and degree of myopia changed rapidly in the first week of form deprivation,then slowing down and stabilizing.The refractive error of the five experimental sub-group are 7.50±1.87D,4.95±2.60D,1.63±1.70D,-1.9±2.46D,-0.275±2.92D;The normal control groups are 8.40±1.82D,7.15±1.56D,6.25±1.39D,6.80±1.48D,3.95±1.28D.The differences of the 4,7,14,21days are statistically siguificant(P＜0.01).The axial length of the five experimental sub-group are 7.70±0.05mm,7.83±0.04 mm,7.88±0.01 mm,7.90±0.02 mm,7.93±0.04 mm;The normal control groups are 7.69±0.03 mm,7.74±0.07 mm,7.74±0.02 mm,7.80±0.03 mm,7.81±0.02 mm.The differences of the 4,7,14,21days are statistically significant(P＜0.01).Histopathologic examination showed thinning of posterior sclera in treated eyes.Collagen fibrillar diameters of sclera in the posterior segment of formed deprivation were obviously smaller and the space between the fibers was larger than that of control eyes.Five sub-group of form deprivation eyes average diameter fibers are 101.9896nm,67.44323nm,52.2256nm,49.7558nm,43.573nm respectively.The normal control eyes are 114.618nm,105.942nm,97.21nm,88.557nm,84.2168nm.The difference is statistically significant(P＜0.05).The difference of average diameter fibers between the experimental eye and the normal eyes,fellow eyes present peak in the first week.Conclusion Form deprived 4 days made the guinea pigs axial myopia and form deprived 1 day the structure and ultrastructure of the posterior sclera obversly changed.The sclera morphology changes faster than the biology.The first week of form deprivation is the fastigium.
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