What is the macula and what role does it play in the eye?

We are afraid of a diagnosis that sounds like “macular degeneration”, but few people know what the macula is. Other structures of the eye, even if we can’t pinpoint them, are much more familiar to us.

Macula lutea is terra incognita – unexplored land – for most patients.

The walls of the eyeball, recall, consist of three membranes:

• The outer fibrous membrane, which includes the sclera and cornea.
• The central choroid membrane, which includes the iris, ciliary body and choroid.
• The inner membrane consisting of two types of photoreceptors (cones and rods), or retina.

The macula is a small portion of the retinal surface. It gets its name from its yellow coloration, which can be seen when examining the fundus of the eye.

Structure and function of the macula

The macula, unlike the rest of the retina, which is flat, has a small depression in its center, the so-called central pit of the retina(foveola centralis). It is located about 3.5 mm from the edge of the optic nerve disc. In the central fovea of the eye, the density of visual receptors is very high, but – note – this is dominated by cones (in humans there are about 60,000 of them), which are absent in other areas of the eye. In contrast, the periphery of the retina is dominated by rods. The cones in the macula are responsible for distinguishing the three main colors: red, green and blue. The brain, which is able to see these three colors, also notices all others.

The macula also provides us with the greatest visual acuity. This is possible because individual visual receptors located in its area transmit information to the brain via separate nerve fibers, while the transmission of information from other areas of the retina takes place differently – groups of several receptors send information via a single fiber.

The main function of the macula is considered to be so-called central vision. Thanks to this tiny area of the retina, we can see observed objects sharply, perceive details of objects that are small in size and far away and also recognize colors.

AMD – macular degeneration

The macula, like other structures of the eye, “wears out” over time, and as we age we become more vulnerable to its degeneration.

Age-related macular degeneration (AMD, or Age-related Macular Degeneration) affects as many as 30% of people over the age of 70, but the first noticeable symptoms of the disease can be observed as early as 50. It is worth knowing that relatives of a person with AMD have a 20-fold increased risk of macular degeneration compared to the general population. Everything you want to know about AMD can be found on our blog.

Fortunately, the process of macular degeneration in the elderly can be slowed down. Daily diet and supplementation are key.

• Vitamin C (500 mg/day): a powerful antioxidant.
• Vitamin E (200-400 mg/day): very potent responsible for the protection of polyunsaturated fatty acids (PFAs) of photoreceptor cell membranes
• Vitamin A (found in animal products) and provitamin A (found in plant products – the most common form of provitamin A is beta-carotene): the dosage should be determined by a doctor, bearing in mind that compulsive smokers should not supplement beta-carotene. Note that vitamin A consumed in excess can be harmful, as it is the building block for lipofuscin, which forms drusen (deposits of retinal metabolic products, appearing in the macular region and causing poorer vision in low light, the impression of crooked letters or their thickening when reading).
• Zinc and selenium: antioxidants (beware of excess selenium, as this element in excess exhibits pro-oxidant instead of antioxidant effects).
• DHA (docosahexaenoic acid): more than 50% of the free PACs present in the cell membranes of the cones and rods are precisely DHA, which has protective properties (reduces the area of retinal damage in the course of ischemia and hypoxia, accelerates the elimination of lipid residues from the retinal pigment epithelium, and thus reduces the amount of lipofuscin deposited).
• Lutein and zeaxanthin: these are the only antioxidant substances detected in the macula of the human eye. They are the ones included in the yellow pigment of the retina, to which the macula owes its name. Both are blue light filters.

It is worth being aware that in a person 75 years old with a healthy digestive tract, only 20-30% of antioxidants from supplements and 50-60% of antioxidants contained in food are absorbed, and the older and sicker the person, the lower the assimilability.