作者：许军　马立威　刘凌梅　徐艳春    作者单位：1（110005）中国辽宁省沈阳市，中国医科大学附属第四医院眼科；2（125100）中国辽宁省兴城市人民医院五官科

    【摘要】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 vs 0.196mm/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±4.78vs 128.5±3.84 μm），纤维巩膜变薄(12.1±0.9vs 26.9±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±3.32vs 144.3±4.78μm)，纤维层厚度增加(20.6±1.2vs 12.1±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。

    【关键词】  幼鸡　形觉剥夺　近视　巩膜　眼轴　屈光

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

    Jun Xu1, Li-Wei Ma1, Ling-Mei Liu2, Yan-Chun Xu1

    1Department of Ophthalmology, the Fourth Affiliated Hospital of China Medical University, Shenyang 110005, Liaoning Province, China; 2Department of Eye and Otolaryngology, People's Hospital of Xingcheng City, Xingcheng 125100, Liaoning Province, China

    AbstractAIM: 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 pathogenesisMETHODS: 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 A- ultrasound 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, scleral 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. Scleral fibrous layer is thinner and degenerated, companied with form-deprived myopia formation.

    · KEYWORDS: chick；form deprivation；myopia；sclera；axial length; refraction

    0引言

    有研究指出，眼球的生长不仅和其它所有器官一样，受发育机制所调节，也受到视觉输入所引起的反馈机制的调节[1-3]。大量研究表明，视网膜上的视觉活动能够引起眼轴的变化[3,4]。实验性的形觉剥夺性近视（form deprivation myopia , FDM）是近年来作为研究人类高度近视的动物模型。由于其结构和屈光特点与人类剥夺性近视及人类的轴性近视极为相似，即都伴有眼轴的增长及纤维巩膜的变薄、延伸。因此，对动物FDM机制的研究有利于人类近视眼机制的探讨。我们通过制作雏鸡形觉剥夺性近视眼模型及形觉剥夺性近视眼恢复模型来判定视环境的改变对屈光、眼轴及巩膜形态的影响，进而探讨眼轴生长与巩膜形态变化之间的关系，为探讨近视进展的病理机制及进一步防治打下基础。

    1材料和方法

    1.1材料 选用新孵出的普通肉食家鸡25只，体质量 30～45g，沈阳市于洪区华联鸡雏场提供，雌雄兼用。带状检影镜（苏州），眼科A/B型超声诊断仪（天津），手术显微镜（日本），40g/L多聚甲醛固定液，0.1mol/L PBS pH7.4。

    1.2方法 新孵出的普通家鸡20只，孵出后2d，将左眼（作为实验眼）进行形觉剥夺：火棉胶将半透明薄膜制成的眼罩固定到鸡眼眶周围的羽毛上。固定后，剥夺眼可以自由地睁闭；对侧眼（右眼）用火棉胶将中间无薄膜的眼罩固定在其眼眶周围的羽毛上，作为对照眼。其中10只雏鸡眼的剥夺时间为14d，作为形觉剥夺组；另10只剥夺时间为11d，之后去剥夺，允许该剥夺眼有3d恢复的时间，作为形觉剥夺恢复组。另取雏鸡5只10眼作为空白对照组。采用室内饲养，白天用自然光照射，维持12h/12h的黑／昼周期。分别对生后当日雏鸡、形觉剥夺组及形觉剥夺恢复组的雏鸡进行带状检影镜检影验光，A超测量前房深度（anterior chamber depth, ACD）、晶状体厚度（lens thickness, LT）及眼轴长度（axial length, AL）。14d后处死各组雏鸡，迅速取出眼球，40g/L多聚甲醛固定2d后，于眼球中央部做矢状面的纵向切开，石蜡包埋，切片，HE染色，于光镜下观察巩膜形态学的改变，采用图像分析仪提供的Metamorph图像分析软件测量巩膜软骨层（cartilaginous sclera,CS）及纤维层（fibrous sclera,FS）厚度。

    统计学处理：采用SPSS10.0统计软件对结果做统计学处理，用t检验对各组进行比较；采用图像分析仪提供的Metamorph图像分析软件测量巩膜厚度。

    2结果

    2.1屈光检查 雏鸡出生后当日左、右眼的屈光呈远视状态，双眼之间无明显差异（7.6±0.9vs 7.5±1.0 D，P >0.05）。形觉剥夺14d后，剥夺眼形成了高度近视（-12.1±4.3D），与对侧的对照眼（+2.7±0.5D）相比，差异有显著性意义 （P <0.01）；剥夺恢复组的实验眼的屈光（-5.5±1.2D）有所恢复，与对侧未遮盖的对照眼（+2.9±0.7D）相比，差异虽仍具有显著性（P <0.01），但与形觉剥夺组中的遮盖眼 （-12.1±4.3D）相比，差异也具有显著性（P <0.05，表1）。

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