Body processes

Photopic Vision – Function, Task & Diseases

Photopic vision

Photopic vision describes normal color vision via the so-called M, L and S cones , which are photosensorically optimized for the green, red and blue areas. Photopic vision requires a minimum brightness of about 3 to 30 cd/sqm and takes place mainly in the fovea centralis , a small area in the retina . The fovea centralis contains the greatest density of cones for sharp color vision, while in the regions outside the fovea centralis mainly so-called rods are located on the retina, which are much brighter but only enable scotopic vision .

What is photopic vision?

Photopic vision means sharp color vision. It is sensory with the help of the L, M and S cones, which are each optimized for the red, green and blue spectral range and reach their greatest density on the retina in the area of ​​the fovea centralis with a diameter of about 1.5 millimeters.

The particularly sharp vision in the fovea centralis comes about through the nervous interconnection of the color cones of almost 1:1. Almost every single cone is connected to a separate nerve fiber, so that each incident photon can be located relatively precisely in the brain .

The counterpart to photopic brightness vision is scotopic vision in relative darkness, which occurs by means of the light-sensitive rods, which are mainly located outside the fovea centralis on the retina. Although the rods are extremely sensitive to light, they are not able to distinguish colors. This means that scotopic vision is the same as monochromatic vision. In addition, scotopic night vision is associated with a degree of blurring, since many rods have to share a nerve fiber, so the brain cannot localize the incident photons as precisely as with cones.

function & task

We humans are among the diurnal creatures for whom sight is one of the most important sources of information. The ability to see color keenly even allows non-verbal communication to a certain extent . Strong emotions such as excitement, fear or anger are expressed in facial expressions , on the skin by blushing in certain areas and in the visible body language . Capturing nuances of non-verbal communication requires the sharpest possible color vision, i.e. photopic vision.

Photopic, binocular vision also enables three-dimensional vision and thus facilitates orientation in three-dimensional space, including distance estimation. Photopic vision was optimized by evolution in order to offer humans the best possible protection from enemies and other dangers and to make it easier for them to search for food.

Assuming a corresponding minimum illumination of 3 to 30 cd/sqm, photopic vision represents an almost all-encompassing aid in (almost) all situations in life and serves the brain as an orientation aid in the case of incompatible multi-sensory information. In such cases, photopic vision serves as a master impulse against which, in case of doubt, all other sensory impressions are aligned, which in many cases can lead to problems such as spatial disorientation.

Diseases & Ailments

Photopic vision is dependent on both the ambient light conditions and the function of the individual organic components associated with the functionality of the L, M, and S cones. Even if all the components involved are in perfect condition, optical illusions can occur that make it difficult for us to orientate ourselves and can even make us sick to the point of vomiting .

While our brain can compensate for short-term discrepancies between vision and vestibular signals, long-term incompatibilities that can arise from optical illusions lead to problems with discomfort. The discomfort or subsequent vomiting can be interpreted as a protective mechanism. It is intended to prevent any further damage that may be caused by the psychogenic or hallucinogenic substances that may be ingested and on which the discrepancies between sensory feedback may be based.

Diseases and disorders that have a direct impact on photopic vision cover a wide range of causes. Visual disturbances can occur due to an insufficient supply of oxygen and nutrients to the cones due to simple circulatory disorders . The visual disturbances can even be included in a diagnosis as an indicator of circulatory disorders.

In many cases, infectious diseases or genetically determined degeneration of the retina or cones are the cause of visual impairment, such as age-related macular degeneration (AMD). It involves a gradual progressive degeneration of the color sensors in the macula, the yellow spot , or fovea centralis.

Another eye disease called glaucoma , also known as glaucoma, results in impaired vision up to and including loss of vision due to progressive damage and degeneration of the optic nerve .

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.