Adachi-Usami E
Department of Ophthalmology, School of Medicine, Chiba University, Japan.
Jpn J Ophthalmol. 1990;34(1):81-94.
Visual functions in senescence were assessed quantitatively by the pattern reversal visually evoked cortical potentials (VECP) in human subjects and animals. The results obtained in the elderly showed an elevation of contrast threshold, ie, lowered sensitivity, for higher spatial frequency, and a rise in the luminance thresholds. There was also an overall suppression in the temporal frequency curves, a sensitivity decrease for the upper half of the visual field, a blue-yellow defect and a decrease in the amplitude of accommodation. Studies of the pseudophakic eye with an intraocular lens verified that the lower transparency and yellowish changes of the crystalline lens and senile miosis do not entirely account for the depressed visual function in the elderly. The delay of P100 peak latency of the VECP in patients with juvenile Parkinson's disease after cessation of L-dopa indicated the deficiency of dopamine in these patients, which in turn was considered as a clinical model of senescence. Optic nerve fiber counts in mice showed a significant decrease in the aged group. It was considered that there is neuronal senescence other than in the eye itself. The results can be illustrated by the following daily life experience. In the evening, an elderly person would have difficulty in identifying a cat as a calico cat if the cat were atop a wall and running quickly through the visual field. It was surprising, however, that the senescence found in the visual function was not as great as that found in the other sensory organs. As further studies, investigation of the feedback mechanism from the brain to the retina and the compensatory mechanism should be made.
通过对人类受试者和动物的模式翻转视觉诱发电位（VECP）对衰老过程中的视觉功能进行了定量评估。在老年人中获得的结果显示，对于较高空间频率，对比度阈值升高，即敏感度降低，并且亮度阈值升高。在时间频率曲线上也存在整体抑制，视野上半部分的敏感度降低，蓝黄缺陷以及调节幅度减小。对人工晶状体的假晶状体眼的研究证实，晶状体的透明度降低和发黄变化以及老年性瞳孔缩小并不能完全解释老年人视觉功能下降的原因。青少年帕金森病患者停用左旋多巴后VECP的P100峰潜伏期延迟表明这些患者存在多巴胺缺乏，这反过来又被视为衰老的临床模型。小鼠的视神经纤维计数显示老年组有显著减少。人们认为除了眼睛本身之外还存在神经元衰老。以下日常生活经历可以说明这些结果。晚上，如果一只花猫在墙上快速穿过视野，老年人很难将其识别为花猫。然而，令人惊讶的是，视觉功能中发现的衰老程度不如其他感觉器官中发现的衰老程度大。作为进一步的研究，应该对从大脑到视网膜的反馈机制和补偿机制进行研究。
