What Is the Macula?

The Macula is the part of the human eye that registers high-acuity readings of straight-ahead vision. It contains a high density of cone cells, which allow for the perception of colors as well as focused vision. The macula is activated during activities such as watching television, recognizing faces, and reading.

As a yellow spot in the center of the retina, surrounding the optic nerve, the macula also act as a set of "natural sunglasses," absorbing excess light entering the eye and keeping the retina from overexposure. It has a diameter of approximately 5 mm and consists of the central foveola and the surrounding fovea. The foveola, with a diameter of 3.5 mm, has the highest concentration of cone cells in the entire eye, giving it the highest visual acuity anywhere in the eye. As the foveola is furthest back from the cornea, or outer layer of the eye, it is most protected - however, if it is damaged by severe trauma or degenerative disease, the effects are immediately noticeable. Vision gets blurry and the eye makes straight lines look like curves. 

The surrounding fovea has the highest ratio of ganglion (nerve information) cells to photoreceptors, which allows for extreme visual acuity. The ratio is almost one-to-one, meaning each cell is receiving information from a single photoreceptor, which allows for the highest possible level of detail from both the rods and the cones contained within the fovea. The fovea, along with the foveola, are unique adaptations in human beings, allowing us to discriminate color far better than most mammals. Interestingly, due to the fovea's comparative lack of rod-type photoreceptors, which allow for vision under dim light, humans also have among the worst night vision of all mammals. Ancient astronomers, looking at dim stars, would look at the night sky out of the corners of their eyes, because the central location of the macula and its cone-type photoreceptors made it impossible to see dim lights straight on.

The macula comprises less than 1% of retinal area but the nerves that touch it consist of close to 50% of the visual cortex in the brain, further emphasizing its importance in eye health and function.

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