During the last fifteen years the work of many investigators has established a relation between some phases of visual acuity and the state of vitamin A nutrition in animals (for full bibliography see the articles by McCollum and his associates1 and Hecht2). Fridericia and Holm3 showed that night blindness is an early symptom of vitamin A deficiency. Wald4 demonstrated that vitamin A enters into the constitution of the visual purple, which constantly traverses a cycle of breakdown and resynthesis when light falls on the retina. In the absence of a fresh supply of vitamin A carried by the circulation the resynthesis is retarded and the visual threshold of the eye is raised; this is the change underlying the onset of some night blindness.
As a result of these findings it has seemed logical to explore the possibility that night blindness in man (when there is no
CAVENESS HL, SATTERFIELD GH, DANN WJ. CORRELATION OF THE RESULTS OF THE BIOPHOTOMETER TEST WITH THE VITAMIN A CONTENT OF HUMAN BLOOD. Arch Ophthalmol. 1941;25(5):827–832. doi:10.1001/archopht.1941.00870110079008
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