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night blindness |
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night blindness, inability to see normally in subdued light. It is usually a result of vitamin A deficiency. The rod cells, one of two light-sensitive areas of the retina of the eye eye, organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many ..... Click the link for more information. , are impaired in their capacity to produce a chemical compound called rhodopsin, or visual purple, that is necessary for the perception of objects in dim light. Consequently, the visual threshold, or the minimum intensity of light necessary for sight, is greatly increased. Folk medicine has long recognized the role of the ingestion of liver in alleviating the condition, but it was not until the first quarter of the 20th cent. that vitamin A was identified as the crucial element. Treatment of night blindness consists of the oral or intravenous administration of vitamin A. |
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Though we usually get enough Vitamin A from the food we eat to avoid getting night blindness, one of the main side effects of a deficiency of Vitamin A, we can often gain health benefits by using vitamin supplements to increase our ingestion of Vitamin A. Night blindness is difficult to get rid of in a hurry and can be deadly. After a prologue establishing that Dan Lynch (Mike Doyle) and Will Stephenson (Chad Lowe) are second-generation Navy aviators and that the latter suffers from night blindness that severely hampers his piloting abilities, the rest of the play takes place seven years later. |
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night blindness