Synonyms
Medical: Macula Lutea (Latin)
Structure
The yellow spot has a size of about 5mm and can be further distinguished into visual fossa (lat. Fovea Centralis), parafovea (para = next to, adjacent) and perifovea (peri = around something). The visual fossa, which is located in the middle of the yellow spot, is the place of sharpest vision.
It contains only cones, which are responsible for color vision. The parafovea, which is about 0.5 mm wide, is located on the outside, where the proportion of rods increases. Due to their high light sensitivity, rods are important for night vision, but they cannot distinguish colors. The highest density of rods is found in the outer area of the yellow spot, in the perifovea – an area that occupies the outer 1.5mm.
Function of the yellow spot
Due to the high concentration of cones in the central region of the yellow spot, the high resolving power of our central visual field is achieved. However, since cones are not light-sensitive enough for seeing in darkness, the high resolving power of the central region of the yellow spot is not available at night, for example, and we see mainly with the rods of the peri- and parafovea, i.e. the marginal regions in the yellow spot. This is a circumstance that anyone can easily check by trying to fix a very faint star in the sky with their eyes.
The light appears more clearly if you look a little bit past the star you are looking at. The fact that we do not notice this division of tasks and the limitations of the different areas of our field of vision is due to the power of our brain to create a stable image from different impressions by many eye movements. However, since cones are not light sensitive enough for seeing in darkness, the high resolving power of the central region of the yellow spot is not applicable e.g.
at night and we see mainly with the rods of the peri- and parafovea, i.e. the edge regions in the yellow spot. This is a circumstance that anyone can easily check by trying to fix a very faint star in the sky with their eyes. The light appears more clearly if you look a little bit past the star you are looking at. The fact that we do not notice this division of tasks and the limitations of the different areas of our field of vision is due to the power of our brain to create a stable image from different impressions by many eye movements.
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