Nutritional factors and visual function in premature infants

Approximately 5-7 % of all infants are born prematurely, and birth before 3 7 weeks is the most common cause of neonatal mortality, morbidity and long- term disability. Premature infants are poorly equipped for life outside the womb, and oxidant stress has been implicated in the aetiology of visual im pairment in these infants, who are often exposed to increased O-2 concentra tions and high light intensity in neonatal units. The carotenoids lutein an d zeaxanthin, which give the macular area of the eye its yellow colour, are located in the retinal pigment epithelium of the eye. and are believed to play a role in protecting it against oxidative and light damage. The macula r pigments are of dietary origin, and green leafy vegetables are the primar y source of lutein and zeaxanthin. Lutein is one of the five most common ca rotenoids found in the diet. There is current interest in the macular pigme nt in relation to age-related macular degeneration, but these pigments may also have a protective role in the retinal pigment epithelium of the newbor n infant. Little information is available on blood lutein and zeaxanthin le vels in neonates. Levels of lutein in human milk are two to three times hig her than those of beta -carotene, whereas their concentrations in the mothe rs' blood are approximately the same. Human milk is the main dietary source of lutein and zeaxanthin for infants until weaning occurs. The biochemical mechanisms which mediate the transport of the macular carotenoids into the eye are not known, but tubulin has been identified as the major carotenoid -binding protein, and may play a role in the physiology of the macula.