Cone cell

A cone cell, or cone, is one of the three types of photoreceptor cells in the retina of the mammalian eye (and the eyes of other vertebrates and some invertebrates). They are responsible for color vision and function best in bright light conditions. Cones are crucial for visual acuity, allowing us to perceive fine details.

There are typically three types of cone cells, each containing a different photopigment (opsin) sensitive to different wavelengths of light. These are commonly referred to as:

• S-cones (Short-wavelength sensitive cones): Primarily detect blue light.
• M-cones (Medium-wavelength sensitive cones): Primarily detect green light.
• L-cones (Long-wavelength sensitive cones): Primarily detect red light.

The brain interprets the relative signals from these three types of cones to perceive the full spectrum of colors. The distribution and relative abundance of cone types vary across different regions of the retina. The fovea, the central region of the retina responsible for the sharpest vision, is densely packed with cones, particularly L-cones and M-cones, while S-cones are fewer in number in the fovea.

Dysfunction or absence of one or more cone types leads to color blindness (color vision deficiency). This can range from difficulty distinguishing certain colors to a complete inability to perceive color.

Cone cells differ structurally from rod cells, the other type of photoreceptor in the retina, which are primarily responsible for vision in low-light conditions (scotopic vision). Cones are typically shorter and thicker than rods, and their outer segments are conical in shape (hence the name "cone cells"). They also have a faster response time to light stimuli compared to rods.