Koretz J F, Cook C A, Kaufman P L
Center for Biophysics, Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
Invest Ophthalmol Vis Sci. 1997 Mar;38(3):569-78.
To characterize changes in the sagittal dimensions of the human crystalline lens and anterior segment as a function of accommodation, to determine the potential age dependence of these changes, and to evaluate these changes in relation to the development of presbyopia.
Scheimpflug slit-lamp photography, as well as a variety of standard ophthalmologic methods, was used to collect information about lens and anterior segment sagital dimensions in a population of 82 adults with refractive error < or = magnitude of 2.0 diopters and at least 0.25 diopter of accommodation for subjects 18 to 70 years of age. Data were analyzed statistically for dependence on accommodation, age, and age dependence of accommodative rate.
The rate of change per diopter of accommodation for each measured variable within the lens is independent of age for the entire adult age range. With increasing accommodation, the lens becomes thicker and the anterior chamber shallower along the polar axis. This increase in sagittal lens thickness is entirely because of an increase in the thickness of the lens nucleus. Because the anterior and posterior halves of the nucleus increase in thickness at approximately the same rate with accommodation, the increase in lens thickness results from equal changes in the lengths of the anterior and posterior portions.
Because changes along the sagittal axis of the anterior segment with accommodation are independent of age, any explanation of presbyopia that relies on simple changes in the rates of lens thickening and anterior chamber shallowing with age does not hold. In light of other age-related changes in the anterior segment and lens (e.g., increased sharpness of lens curvature, increased lens sagittal thickness, decreased anterior chamber depth), it appears that compensatory mechanisms to preserve far vision with age also preserve the rate of change per diopter of sagittal spacings.
描述人晶状体和眼前节矢状径尺寸随调节的变化情况，确定这些变化潜在的年龄依赖性，并评估这些变化与老花眼发展的关系。
采用Scheimpflug裂隙灯摄影以及多种标准眼科方法，收集了82名年龄在18至70岁、屈光不正度数≤2.0屈光度且调节力至少为0.25屈光度的成年人晶状体和眼前节矢状径尺寸的信息。对数据进行统计学分析，以确定其与调节、年龄以及调节速率的年龄依赖性之间的关系。
在整个成年人年龄范围内，晶状体各测量变量每屈光度调节的变化率与年龄无关。随着调节增加，晶状体沿极轴变厚，前房变浅。晶状体矢状径厚度的增加完全是由于晶状体核厚度的增加。由于核的前半部分和后半部分在调节时厚度增加的速率大致相同，晶状体厚度的增加是由于前后部分长度的等量变化所致。
由于眼前节矢状轴随调节的变化与年龄无关，任何依赖晶状体增厚和前房变浅速率随年龄简单变化来解释老花眼的观点都不成立。鉴于眼前节和晶状体的其他与年龄相关的变化（例如，晶状体曲率锐度增加、晶状体矢状径厚度增加、前房深度减小），似乎随着年龄增长保持远视力的代偿机制也保持了矢状间距每屈光度的变化率。
