Your free myERCO account allows you to mark items, create product lists for your projects and request quotes. You also have continuous access to all ERCO media in the download area.


You have collected articles in your watchlist

Technical environment

Technical environment

Global standard 220V-240V/50Hz-60Hz
Standard for USA/Canada 120V/60Hz, 277V/60Hz
  • 中文

Our contents are shown to you in English. Product data is displayed for a technical region using USA/Canada 120V/60Hz, 277V/50Hz-60Hz.

Receptors (eye): the receiver cells for light stimuli

Illustration of the different receptors in the eye.

Receptors in the eye are sensory cells that respond to light stimuli and transmit signals via the nerves to the brain. Humans have three different types of light-sensitive receptors for visual and non-visual perception.

Would you like to find out more?

Overview of receptors

What are the types of receptors?

The human eye has three different types of light-sensitive receptors: rods, cones and photosensitive ganglion cells.
Rods and cones enable visual perception, i.e. vision. The light-sensitive rods let us see differences in brightness even at night

The special features of night vision are:
  • The disappearance of colors
  • The low visual acuity
  • The better visibility of faint objects in the periphery of the field of view

Cones on the other hand serve to perceive colors and require more light. In darkness, humans perceive no colors but only shades of grey. It is only with increasing luminance that the eye switches from night vision (scotopic vision) via twilight vision (mesopic vision) to colored daytime vision (photopic vision) .

This distinguishes the cone system:
  • A low sensitivity to light
  • Concentration mainly in the central area around the fovea
  • Perception of colors and high visual acuity when looking at objects that are fixed, i.e. whose image falls into the fovea

The photosensitive ganglion cells represent a special type of photoreceptor. They have only been analyzed more closely since the 1990s. They are not used for seeing like the other two receptors, but use brightness information to control e.g. the circadian rhythm, the "internal clock" of humans during the day and night.

How are receptors arranged?

A closer look shows that the receptors in the retina are not arranged in a uniform grid. The spatial distribution of the cones and rods is not uniform. At one point, called the "blind spot", there are no receptors at all because this is where the bundled optic nerves enter the retina. Contrarily, there is also an area of particularly high receptor density known as the fovea, which is located at the focal point of the lens. This central area contains a highly concentrated number of cones. However, the density of cones decreases sharply towards the periphery. This is where the rods sit, which are completely absent in the fovea.

In contrast to rod vision, the entire field of vision is not perceived uniformly. The focus of perception is in its center. However, the edge of the field of view is not completely without influence: if interesting phenomena are perceived there the gaze is involuntarily directed to this point, which is then imaged in the fovea to be perceived more precisely. An important reason for this shift in the direction of gaze is, in addition to movements that occur and noticeable colors or patterns, the presence of high luminance levels – people's gaze and attention can therefore be directed by light.

The photosensitive ganglion cells are distributed across the entire retina. However, these receptors react particularly sensitively in the lower area and towards the nose.

How many receptors does the eye have?

The retina's receptor layer has approximately 6 million cones and 120 million rods. The exact quantity varies from person to person.


People with too few or no rods in the retina suffer from night blindness. People who have no cones or non-functional cones are color-blind.

Would you like to find out more?

Further topics on the human eye

Do you need further information?

You can contact your regional contact partner via:

You can gladly send us an e-mail or ask your question here

Your data will be handled confidentially. For further information see Data protection declaration.




Planning light

About ERCO