The Effects of Lutein and Zeaxanthin Supplementation on Vision in Patients With Albinism

Ocular and oculocutaneous albinism represent a spectrum of disorders with absent or significantly diminished amount of melanin either across different body tissues - skin, hair, eye (Oculocutaneous Albinism 1 and 2), or exclusively in eye tissues only (Ocular Albinism 1) . The functionality and the clinical findings are diverse (the phenotype), and no direct correlation has been established to the underlying mutations (genotype). The common ocular phenotype includes iris transillumination, foveal hypoplasia, nystagmus, reduced visual acuity, refractive error, photosensitivity and abnormal development of the visual pathways with characteristic abnormal routing of ganglion cell axons in the chiasma, resulting in abnormal visually evoked potentials. Current treatment options are limited to optical methods and low vision aids. The mechanism of melanin pigment formation in the RPE cells and its role in the visual pathways and structures development is not completely understood, but a correlation was found between the amount of fundus pigmentation and visual function in albino patients. The absent pigmentation within the retinal pigment epithelium (RPE) may thus contribute to visual performance deficits. The macular pigment (MP) consists of two main carotenoids, lutein and zeaxanthin, which are concentrated in the macular region of the retina. MP is hypothesized to function via a protective mechanism by absorbing blue light incident on the retina thereby reducing oxidative damage to the underlying photoreceptors. It is also thought to improve visual function via reduction of chromatic aberration and glare. It is currently unclear as to how the variability in macular pigment optical density (MPOD) affects congenital retinal conditions. The MP would, however, be a hypothetical and good candidate to improve visual performance - simply by increasing pigmentation, reducing light scatter and thus glare sensitivity. As this pigment is not produced in the retina, but is absorbed via diet, it can be manipulated by alteration in diet and supplementation thereby providing potential therapy for retinal diseases. It is however necessary first to see if MPOD levels are measurable in this disorder before dietary advice can be provided after completion of the LUVIA study. Further to this, evaluation of both the structural and functional properties of the retina will provide greater insight into the possible function of MP in this retinal disease including whether supplementation would be of benefit.