雏鸡形觉剥夺眼屈光状态、眼轴长度及巩膜形态学改变之间的关系

Relationship of refractive status,axial length,and scleral metamorphic change in chicken form deprivation eyes

目的:研究雏鸡形觉剥夺性近视眼及形觉剥夺性近视眼恢复模型的屈光状态和眼轴长度的变化,并观察后极部巩膜的形态学改变,为探讨轴性近视的发病机制打下基础。方法:选用新孵出的普通肉食家鸡25只,采用半透明薄膜眼罩遮盖的方法对左眼进行形觉剥夺14d(形觉剥夺组)或遮盖11d后,去遮盖3d(形觉剥夺恢复组)。两组右眼作为对照眼。分别对两实验组进行检影验光及A超测量眼轴长度。达规定时限后处死动物,取出眼球,于眼球中央部做矢状面的纵向切开,行HE染色,光镜下观察巩膜形态学改变,采用Metamorph图像分析软件测量巩膜软骨层和纤维层厚度。结果:形觉剥夺组剥夺眼形成了高度近视(-12.1±4.3D),眼轴增长(9.86±0.38mm),与右眼的屈光(+2.7±0.5D)和眼轴(8.71±0.28mm)相比,差异具有显著性(P<0.01);形觉剥夺恢复3d与剥夺14d相比,屈光度(-5.5±1.2D)减低(P<0.05),眼轴长度虽无明显变化(P>0.05),但眼轴增长速度明显减慢(0.003mm/d vs0.196mm/d),甚至比对侧对照眼的增长速度(0.116mm/d)还要慢。各组前房深度、晶状体厚度无明显变化(P>0.05)。巩膜HE染色及厚度测量可见,剥夺眼的软骨巩膜增厚(144.3±4.78vs128.5±3.84μm),纤维巩膜变薄(12.1±0.9vs26.9±1.7μm),纤维层细胞数目减少,排列紊乱;剥夺恢复眼与剥夺眼相比,软骨层厚度变薄(135.4±3.32vs144.3±4.78μm),纤维层厚度增加(20.6±1.2vs12.1±0.9μm),分别接近对侧对照眼的软骨层和纤维层厚度。结论:形觉剥夺可导致幼鸡眼轴增长,诱发轴性近视,此眼轴增长主要是眼球后段的增长。在幼鸡发育期间去剥夺后,近视屈光度减低,眼轴增长速度减慢。伴随形觉剥夺性近视的形成,剥夺眼的纤维巩膜变薄,发生退行性改变。

AIM： To study the changes of refractive status and axial length in chicken form deprivation myopia and its recovery model, to observe the metamorphism of posterior sclera and to lay foundation for investigation of axial myopia pathogenesis METHODS： Twenty-five newly incubated chicken were selected. Their left eyes were covered with semi-translucent membrane to deprive form perception for 14 days （form-deprivation group）, or covered for 11 days followed by uncovered for 3 days （recovery group）. Unoccluded eyes in either group served as control eyes respectively. Retinoscopy and Aultra- sound were conducted to collect the refraction and axial length data. Chicken were executed right at time limit .Eye balls were then extracted and dissected at sagittal plane in the middle. After HE staining, sclera sections were observed under light microscope .thickness of scleral cartilage layer and fibrous layer were obtained by Metamorph image analysis software. RESULTS： High myopia （-12.1±4.3D） and axial lengthening （9.86± 0.38mm） were found in form deprivation eyes, and were significantly different from refraction （＋2.7±0.5D） and axial length （8.71±0.28mm） of the lateral control eye（P〈0.01）. After recovery from form deprivation for 3 days, refraction（-5.5±1.2D） decreased compared to chicken occluded for 14 days （P〈0.05）, while axial length was the same （P 〉0.05）. However, the length growth rate was slower （0.003mm/day vs 0.196mm/day）, and was even slower than lateral control eye （0.116mm/day）. Anterior chamber depth, lens thickness showed no changes （P 〉0.05） in every group. As for HE staining and thickness measurement, scleral cartilage layer was thickened （144.3±4.78 vs 128.5±3.84μm）, fibrous layer was thinner （12.1±4.78 vs 26.9±1.7μm）, fiber cell number decreased and disarranged in form-deprivation group. Comparably, sckeral cartilage layer in deprivation recovery group was thinner （135.4±3.32 vs 144.3±4.78μm）, and fibrous layer was thickened （20.61±1.2 vs 12.1±0.9μm） than deprivation group; in addition, those data in deprivation recovery group were close to those in lateral control group. CONCLUSION： Form deprivation can lead to prolonged axial length in chicken, which is mainly the lengthening of posterior segment, thus induce axial myopia. After deprivation is removed during the chicken development period, myopic refractive power decreases, and axial growth rate slows down. Sderal fibrous layer is thinner and degenerated, companied with form-deprived myopia formation.