Light Advantageous for Diabetics

Sleeping with the lights on may be the next advice for diabetics according to a current publication. Scientists suggest night-time illumination could help prevent the onset of diabetic retinopathy, a condition which can result in severe visual impairment. The condition affects about 25 per cent of people who suffer from diabetes and is the largest cause of the onset of adult blindness in Britain.
             
Diabetes causes impaired functioning of blood capillaries, reducing oxygen supply throughout the body. Rod receptors in the retina, which are responsible for night vision, are most sensitive to this change because they have the highest oxygen demand of any cell in the body at low levels of illumination.

A human eye exposed to bright light then total darkness can ramp up its light sensitivity by a factor of about 100,000 times in 30 minutes. This dark adaptation is achieved mainly by neural and chemical processes in the retina. Rod receptors used for night vision are so dependent upon adequate oxygen supply that dark adaptation of normal eyes has been reported to be diminished at moderate altitudes above sea level due to the slight reduction in available oxygen.

The normal eye is only just capable of providing adequate oxygen to the retina during night vision. Even in early stages of the disease, diabetics suffer a lack of oxygen (hypoxia) during dark adaptation. This would be expected to occur in the vicinity of the rods, in the deeper layers of the retina, but the retinopathy develops nearer to the surface of the retina. 

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灯光对糖尿病患者有益
当前出版的一本刊物称，糖尿病患者下次可能得到的忠告就是开灯睡觉。科学家们认为，夜间照明可能会有助于预防糖尿病视网膜病的产生，这种病能导致严重的视力损伤。有大约百分之二十五的糖尿病患者患有视网膜病，而且在英国，这种病是造成成年人失明的最主要的病因。
糖尿病造成毛细血管功能衰退，从而减少全身的氧气供应。视网膜里的视杆感受器负责夜视，他们对这种变化最敏感，这是因为在低照明条件下，人体内所有细胞中只有视杆感受器对氧气的需求量最高。
当人的眼睛在先接触到亮光然后处于完全黑暗的过程当中，它上涨的光灵敏系数为30分种约10万倍。这种暗适应主要是通过视网膜里神经反应过程和化学变化过程来完成的。用于夜视力功能的视杆感受器非常依赖充足的氧气供应，甚至有报道说，在中等海拔高度的地方，由于可供氧气的轻微减少，正常眼睛的暗适应能力会衰退。
在夜视过程中正常眼睛只是正好能够向视网膜供应充足的氧气。甚至在糖尿病的早期阶段里，糖尿病患者在暗适应过程中会缺少氧气。据预计，这种情况可能会发生在视杆附近、视网膜较深层的地方，但是视网膜病则发生在更靠近视网膜表面的地方。