Sun W S, Baker R S, Chuke J C, Rouholiman B R, Hasan S A, Gaza W, Stava M W, Porter J D
Department of Opthalmology, University of Kentucky Medical Center, Lexington 40536-0284, USA.
Invest Ophthalmol Vis Sci. 1997 Jan;38(1):92-9.
The authors analyzed eyelid kinematics in normal aging subjects to test the hypothesis that eyelid movements exhibit age-related changes and that blink disorders prevalent among the elderly, in turn, represent an outcome of normal aging processes.
The electromagnetic search coil technique was used to study blinks in normal human subjects for each decade from 40 to 89 years. Blink metrics (amplitude, peak velocity, and duration), main sequence relationships, and conjugacy were assessed.
Mean amplitude and peak velocity of blinks decreased with age for spontaneous blinks and, to a lesser extent, for voluntary blinks. Some but not all, of this decline could be attributed to a peripheral phenomenon, narrowed palpebral fissure width. The spontaneous blink down phase main sequence slope also declined with age. By contrast, blink rate and the coordination of movements of the two eyelids--blink conjugacy--exhibited no change.
These data demonstrate that disorders of blink systems typically seen in persons 50 years of age or older occur on a background of normal age-dependent changes in eyelid kinematics. Alterations in main sequence slope imply the operation of central adaptive systems during aging. Reduction in main sequence slope is interpreted as a reduction in aggregate orbicularis oculi motoneuron activity. Such a central neurologic adjustment in the motor output of blink systems may serve to compensate for an age-related increase in blink reflex excitability. Compensatory reduction in the main sequence relationship may offset a potentially hyperexcitable blink reflex, thereby reducing the likelihood of disorders such as blepharospasm. The authors conclude that although there are changes in the kinematics of blinking with age, such changes do not necessarily predispose an aging population to eyelid motility disorders.
作者分析了正常衰老受试者的眼睑运动学，以验证以下假设：眼睑运动存在与年龄相关的变化，而老年人中普遍存在的眨眼障碍反过来代表了正常衰老过程的结果。
采用电磁搜索线圈技术，对40至89岁每个年龄段的正常人类受试者的眨眼情况进行研究。评估眨眼指标（幅度、峰值速度和持续时间）、主序列关系和共轭性。
自发性眨眼的平均幅度和峰值速度随年龄增长而下降，自主性眨眼的下降幅度较小。这种下降部分但并非全部可归因于一种外周现象，即睑裂宽度变窄。自发性眨眼向下阶段的主序列斜率也随年龄下降。相比之下，眨眼频率和双眼睑运动的协调性——眨眼共轭性——没有变化。
这些数据表明，50岁及以上人群中常见的眨眼系统障碍是在眼睑运动学正常的年龄依赖性变化背景下发生的。主序列斜率的改变意味着衰老过程中中枢适应性系统的运作。主序列斜率的降低被解释为眼轮匝肌运动神经元总体活动的减少。眨眼系统运动输出的这种中枢神经调节可能有助于补偿与年龄相关的眨眼反射兴奋性增加。主序列关系的代偿性降低可能抵消潜在的过度兴奋的眨眼反射，从而降低诸如眼睑痉挛等障碍的发生可能性。作者得出结论，尽管眨眼的运动学随年龄有所变化，但这些变化不一定使老年人群易患眼睑运动障碍。
