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- Glossary
Photopigment
Photopigments are light-sensitive molecules in the receptors of the retina. When photons (particles of light) strike the photopigment, it isomerizes, triggering a cascade of various processes. In this way, light is converted into a nerve impulse. All rods have the same type of photopigment, while the cones have one of three possible photopigments.
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- Glossary
Ganglion cell
The ganglion cell bundles the signals from the photoreceptors in the retina and transmits them via its axons (long, fiber-like extensions of a nerve cell. All of these axons together form the optic nerve.
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- Glossary
Macula
The area of the retina with the highest density of photoreceptors. Due to this high "resolution," we see very sharply here. The diameter of the macula in humans is approximately 5 mm. The fovea centralis is located in the center of the macula.
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Horizontal cell
Horizontal cells are nerve cells in the retina. They form a lateral connection between photoreceptors and bipolar cells. In this way, they increase the contrast of what is seen.
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- Glossary
Cornea
The cornea is the transparent front part of the outer layer of the eye. It is involved in refracting light, ensuring that the image of a distant object falls on the point of sharpest vision on the retina.
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- Glossary
Convergence
Convergence of neurons occurs when several neurons are connected synaptically to a single transmitting neuron. In the eye, for example, information received by up to 130 receptors is transmitted to only one neuron in the retina. The opposite is divergence, when one neuron transmits signals to several other neurons.
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- Glossary
Lateral inhibition
Lateral inhibition is a principle of neural stimulus processing, according to which the retina, among other things, is structured. There, the nerve cells of an area are interconnected in such a way that when they are excited, they inhibit the activity of the surrounding neurons.
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- Glossary
Opsin
Opsins are light-sensitive proteins in the retina that, together with the chromophore retinal, absorb light and convert it into electrical signals. The following opsins occur in humans: rhodopsin in rods, for twilight vision, S-opsin → short-wave cones (blue), M-opsin → medium-wave cones (green), L-opsin → long-wave cones (red). These three cone opsins enable color vision.
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- Glossary
Papilla
The optic nerve leaves the eye at the papilla, the optic disc. Since there are no photoreceptors at this point on the retina, the optic disc creates a blind spot.
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- Glossary
Rhodopsin
A specific opsin found in the rods of the retina.
