The macula – what is it actually?
If you could travel straight into a person's eye while sitting on a beam of light, you would first penetrate the cornea, then pass through the pupil with its iris, and finally cross the lens, which would guide you precisely to a specific point. The journey then continues through the vitreous body until you reach your destination: the retina. The point in question is located exactly in the middle of this spherical skin inside the eye, and you should immediately notice it because of its color. It is called the yellow spot (Macula Lutea in Latin or, in German, Makula). What is this strange area in the eye all about?
A man undergoing an eye examination.
The Yellow Spot is so called because it is – well – yellow
The yellow spot has a diameter of between 3 mm and 5 mm and owes its name to the fact that there are relatively few blood vessels in this area. While the rest of the retina is criss-crossed by countless fine veins, the macula is mainly reserved for the photoreceptor cells and pigments - but more on that later. While the rest of the retina shimmers reddish because of the many vessels, the macula is visible as a yellow dot. It was discovered by the German anatomist Samuel Thomas von Soemmerring (born 1755) while dissecting human eyes. Since Goethe's contemporary was apparently not blessed with his linguistic creativity, he gave the abnormality in the eye the rather unpoetic name: yellow spot.
The World: Sharp and in Color Thanks to the Macula
The fact that the macula is located exactly on the central visual axis is of course no coincidence. The density of color-sensitive sensory cells, the so-called cones, is highest in its center. The cones are particularly densely packed in the center of the macula, in the funnel-shaped fovea centralis; this is the point with the highest visual acuity - nowhere else in the eye is such a fine resolution of the incoming information possible. The further you move away from the center of the macula, the more rods join the cones. These sensory cells are more responsible for light-dark vision and help us to be able to see things in twilight or darkness. Outside the macula, the cones hardly play any role: on the retina, only about one in twenty sensory cells is responsible for fine resolution and the perception of colors.
The Blind Spot and Our Tricky Brain
The yellow spot should not be confused with the blind spot, even though the two regions are very close to one another. The blind spot is located approximately 15 degrees towards the nose; there are no photoreceptors here, as this is where the nerve fibers of the retina converge. From there, the sensory information travels along the optic nerve towards the brain. At this point, you actually see absolutely nothing. However, the image that we see is created in the brain - and this ensures that the missing information is supplemented with memory images or image impressions from the other eye. We do not subjectively perceive the blind spot in this way. The blind spot is in a sense the opposite of the yellow spot, but both are essential for the functioning of the fascinating organ that is the eye. In our video, Dr. Richard Püschner shows the path of the light entering the eye to the macula - the yellow spot that gives us all the colors.
