Heys Karl Robert, Cram Sandra Leigh, Truscott Roger John Willis
Australian Cataract Research Foundation, University of Wollongong, Wollongong, Australia.
Mol Vis. 2004 Dec 16;10:956-63.
To determine the stiffness of different regions of human lenses as a function of age, and to correlate the biophysical measurements in the lens center with nuclear water content.
A custom made probe fitted to a dynamic mechanical analyzer was employed to measure stiffness values at 1 mm increments across equatorial sections of individual human lenses. Thermogravimetric analysis was used to determine the percentage water content in the nuclei of human lenses.
There was a pronounced increase in lens stiffness over the age range from 14 to 78. In the nucleus, stiffness values varied almost 1,000 fold over this age range, with the largest change observed in lenses between the ages of 20 to 60. Nuclear stiffness values increased on average by a factor of 450. By contrast, in the cortex the average increase in stiffness was approximately 20 fold over this same time period. In lenses younger than age 30, the nucleus was found to be softer than the cortex. This was true for all six lenses examined. In contrast all lenses older than 30 were characterized by having nuclear values higher than those of the cortex. In lenses over the age of 50, the lens nucleus was typically an order of magnitude more rigid than that of the cortex. The crossover age, when the cortical and nuclear stiffness values were similar, was in the 30s. There was no significant change in the water content of the human lens nucleus from age 13 to age 82.
There is a marked increase in the stiffness of the human lens with age. This is most pronounced in the nucleus. Since in vivo data indicate that the nucleus must change shape significantly during accommodation, it is highly likely that these measured changes in physical properties will markedly diminish the ability of the lens to accommodate, and thus may be a major contributing factor to presbyopia. Since there was no measurable difference in the water contents of the nuclear regions of the lenses, this marked increase in stiffness is not due to compaction of the lens nucleus.
确定人晶状体不同区域的硬度随年龄的变化情况，并将晶状体中心的生物物理测量结果与核含水量相关联。
使用安装在动态力学分析仪上的定制探头，以1毫米的增量测量各个人类晶状体赤道截面的硬度值。采用热重分析法测定人晶状体核中的含水量百分比。
在14至78岁的年龄范围内，晶状体硬度显著增加。在核中，硬度值在这个年龄范围内变化近1000倍，在20至60岁的晶状体中观察到最大变化。核硬度值平均增加了450倍。相比之下，在皮质中，同一时期硬度的平均增加约为20倍。在30岁以下的晶状体中，发现核比皮质软。所有检测的六个晶状体均是如此。相比之下，所有30岁以上的晶状体其核的值均高于皮质。在50岁以上的晶状体中，晶状体核通常比皮质硬一个数量级。皮质和核硬度值相似时的交叉年龄在30多岁。从13岁到82岁，人晶状体核的含水量没有显著变化。
人晶状体的硬度随年龄显著增加。这在核中最为明显。由于体内数据表明核在调节过程中必须显著改变形状，很有可能这些测量到的物理性质变化将显著降低晶状体的调节能力，因此可能是老花眼的一个主要促成因素。由于晶状体核区域的含水量没有可测量的差异，这种硬度的显著增加不是由于晶状体核的压实。
