a b c d e Foster, David H. (2011). "Color Constancy". Vision Research. 51 (7): 674–700. doi: 10.1016/j.visres.2010.09.006. PMID 20849875. S2CID 1399339. Land, Edwin (December 1977). "The Retinex Theory of Color Vision". Scientific American. 237 (6): 108–28. Bibcode: 1977SciAm.237f.108L. doi: 10.1038/scientificamerican1277-108. PMID 929159. Conway, BR; Livingstone, MS (2006). "Spatial and Temporal Properties of Cone Signals in Alert Macaque Primary Visual Cortex (V1)". Journal of Neuroscience. 26 (42): 10826–46. doi: 10.1523/jneurosci.2091-06.2006. PMC 2963176. PMID 17050721. [cover illustration]. Metamerism, the perceiving of colors within two separate scenes, can help to inform research regarding color constancy. [24] [25] Research suggests that when competing chromatic stimuli are presented, spatial comparisons must be completed early in the visual system. For example, when subjects are presented stimuli in a dichoptic fashion, an array of colors and a void color, such as grey, and are told to focus on a specific color of the array, the void color appears different than when perceived in a binocular fashion. [26] This means that color judgements, as they relate to spatial comparisons, must be completed at or prior to the V1 monocular neurons. [26] [27] [28] If spatial comparisons occur later in the visual system such as in cortical area V4, the brain would be able to perceive both the color and void color as though they were seen in a binocular fashion.

Lutein is concentrated in a part of the retina called the macula, which is responsible for the fine vision needed for reading and recognising faces. Some lutein is also converted into another carotenoid – zeaxanthin – and together they act like 'nature's sunglasses' to filter out damaging blue light. Abdel-Aal, E.S., Akhtar, H., Zaheer, K. and Ali, R.(2013). Dietary sources of lutein and zeaxanthin carotenoids and their role in eye health. Nutrients Bone, R. A., Landrum, J. T., Mayne, S. T., Gomez, C. M., Tibor, S. E., and Twaroska, E. E. Macular pigment in donor eyes with and without AMD: a case-control study. Invest Ophthalmol.Vis.Sci. 2001;42(1):235-240. View abstract. Here "Reprinted in McCann" refers to McCann, M., ed. 1993. Edwin H. Land's Essays. Springfield, Va.: Society for Imaging Science and Technology. Bartlett, H. and Eperjesi, F. A randomised controlled trial investigating the effect of nutritional supplementation on visual function in normal, and age-related macular disease affected eyes: design and methodology [ISRCTN78467674]. Nutr.J. 10-10-2003;2:12. View abstract.a b Hood, D.C. (1998). "Lower-Level Visual Processing and Models of Light Adaptation". Annual Review of Psychology. 49: 503–535. doi: 10.1146/annurev.psych.49.1.503. PMID 9496631. S2CID 12490019. Djuric, Z., Uhley, V. E., Naegeli, L., Lababidi, S., Macha, S., and Heilbrun, L. K. Plasma carotenoids, tocopherols, and antioxidant capacity in a 12-week intervention study to reduce fat and/or energy intakes. Nutrition 2003;19(3):244-249. View abstract. We add vitamin B2, which is proven to contribute to normal vision. This vitamin also acts as an antioxidant, combating the cell damage that occurs over time due to everyday environmental stresses. What's more, we use lutein and zeaxanthin that come from a natural source of marigolds and are purified in a standardised extraction process to ensure that each vegan tablet contains 20mg lutein and 2,000µg zeaxanthin. Who is this for? Retinex®, Retinex Max® and OptiVision® all contain lutein and zeaxanthin, but in different strengths and with different complementary eye vitamins.

It's a vegan formulation that's specially designed to support your vision and eye health. While extended lifespans are certainly something to celebrate, they also mean that age−related sight problems are on the rise, so it's important to give your precious peepers plenty of support. Retinex® contains natural lutein and zeaxanthin, two powerful carotenoids found in high concentrations in the macula, the 'seeing' part of your eye. With the increased use of computers and smartphones, it's also encouraging to know that lutein and zeaxanthin absorb blue light! We've also combined them with the full amount of vitamin B2 that the EU recommends all adults should consume daily. This powerful nutrient is proven to contribute to normal vision and to act as an antioxidant, combating the cell damage that occurs over time due to everyday environmental stresses. Why is ours better?

Reduce your risks

People who use a computer screen regularly can also benefit from taking lutein supplements to protect against the blue light these screens emit. In 37 healthy volunteers, aged 22 to 30 years, those taking lutein supplements for 12 weeks showed improved visual function, with significantly improved contrast sensitivity and a trend towards increased visual acuity. Typical treatment involves eye drops known as artificial tears. These can be successful but may need to be used frequently to prevent burning, itching, grittiness and painful ulceration. OptiVision®, the premium lutein supplement in the Healthspan range, includes a daily tablet and capsule. Each tablet contains 20mg lutein and 2000µg zeaxanthin, plus vitamin B2 and zinc 3 to support normal vision. Copper and vitamins C and E help protect your cells from oxidative stress. 4

This condition usually occurs when the fluid that fills the front part of your eye can't drain away properly, increasing pressure inside the eye. The eye needs pressure to keep the eyeball in shape, but if it gets too high, it squeezes the optic nerve, which carries visual information from the eye to the brain. This can lead to irreversible sight loss if it's not detected and treated. Who gets it? Bartlett, H. E. and Eperjesi, F. A randomised controlled trial investigating the effect of lutein and antioxidant dietary supplementation on visual function in healthy eyes. Clin.Nutr. 2008;27(2):218-227. View abstract. a b Jameson, D.; Hurvich, L. M. (1989). "Essay concerning color constancy". Annual Review of Psychology. 40: 1–22. doi: 10.1146/annurev.psych.40.1.1. PMID 2648972. Broekmans, W. M., Berendschot, T. T., Klopping-Ketelaars, I. A., de Vries, A. J., Goldbohm, R. A., Tijburg, L. B., Kardinaal, A. F., and van Poppel, G. Macular pigment density in relation to serum and adipose tissue concentrations of lutein and serum concentrations of zeaxanthin. Am.J.Clin.Nutr. 2002;76(3):595-603. View abstract.It's a vegan formulation that's specially designed to support your vision and the health of your eyes over the long term. While extended lifespans are certainly something to celebrate, they also mean that age−related sight problems are on the rise, so it's important to give your precious eyes plenty of support. Retinex® Max contains natural lutein and zeaxanthin, two powerful carotenoids found in high concentrations in the macula, the 'seeing' part of your eye. Lutein and zeaxanthin are also proven to absorb blue light, which is an added bonus for those who spend a lot of time with smartphones and computers! Why is ours better?