Retinitis pigmentosa vitamin a serum levels in relation to clinical findings

Abstract

The majority of subjects affected with retinitis pigmentosa show a subnormal level of vitamin A and of carotenoids in the blood. This feature persists for many years both in hereditary and non-hereditary cases, and in a number of their unaffected relatives. The absorption of vitamin A has been found to be normal, and the serum level of vitamin A can be raised by continuous therapy with vitamin A, vitamin E, vitamin A and E together, or by the administration of β-carotene. It falls again within a few weeks of the cessation of treatment. The promotion of the blood vitamin A to a normal level over a considerable period has a beneficial effect on the retina in an appreciable number of cases. It is made evident by an increase of over 10% in the total area of both visual fields (binocular field area) and by an improvement in dark adaptation as shown by the measurements of the cone and rod threshold. The degree of vitamin A deficiency which is found in retinitis pigmentosa is discussed in relation to the carotenoid/vitamin A ratio in the blood and to the mode of action of the vitamins selected for therapeutic trial.