To the Editor:
—From 1956 to 1958, animal studies were performed using newborn white rats1 which demonstrated that subminimal doses of 11-cis vitamin A will protect the retina of a newborn rat and prevent retinal rod degeneration but would not prevent somatic changes of vitamin A deficiency. This indicated that in the newborn white rat, 11-cis vitamin A was necessary for the metabolism and viability of the retinal rods.The vitamin A in our normal diets and in vitamin capsules is in the all-trans form and must be isomerized somewhere in the body to produce 11-cis vitamin A to be utilized by the retinal rods. In retinitis pigmentosa there is progressive degeneration of the retinal rods. It is postulated that individuals with this disease have an hereditary or constitutional inability to make the normal isomerization from all-trans to 11-cis vitamin A, thereby resulting in gradual retinal rod degeneration. The
Chatzinoff AB, Haig C. I I-CIS VITAMIN A IN THE TREATMENT OF RETINITIS PIGMENTOSA. Arch Ophthalmol. 1962;68(1):149–150. doi:10.1001/archopht.1962.00960030153029
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