Clarity, Color, & Sight through the Dark.
Have you ever wondered exactly how our eyes grant us the ability to see all of life’s beauty?
Specialized cells - Photoreceptors - are responsible for converting the light in images into electrical signals, which are then sent to the brain. These photoreceptors are what give us our color vision and night vision. We have 2 types of photoreceptors: Rods and Cones.
Cones - The Supermen
Photopic vision - vision in bright light / Color vision
Like the Man of Steel, our cones allow us to see fine detailed vision. Cones are light-sensitive cells that detect a wide spectrum of light, enabling us the power to perceive color. We have 3 types of cone cells - Red-sensing, Green-sensing, and Blue-sensing cones.
Millions of cone cells are concentrated in the central region of our retina - the Fovea - which is also our central vision. Cones are the reason we humans have sharp acuity and fine focused vision.
Interesting Fact:
Color blindness occurs when some of our cones are missing, not working properly, or are detecting a different color than the norm.
In severe color blindness, all 3 cones are absent. For the case of mild color blindness, all 3 cones are present, but 1 cone is not working quite right.
Did you know that dolphins are color blind because they lack the cones that perceive color? Alternatively, they use sound - Echolocation - to sense their environment.
Rods - The Batmen
scotopic vision - Vision in dim light
Similar to the Dark Knight, our rods thrive in the night. As brightness dims around us, our eyes switch from cone vision to rod vision. Rods are 500 to 1,000x more sensitive to light, enabling them with the skill to capture even the weakest light impulses to detect vision in the dark. Rods can’t detect color, which is why at night, we see everything in shades of gray - Achromatic.
We have over 100 million rods in our peripheral retina, which gives us our peripheral vision. Since rods are highly sensitive, they allow us to see both while we are in motion and when objects are in motion. In survival, our highly receptive rods detect a threat from our peripheral vision by its motion, thereby alerting us to turn our eye’s attention to it.
Interesting Fact:
A rare disease, Retinitis Pigmentosa, results from genetic mutations that elicit a slow death of rod cells. This begins with loss of one’s peripheral vision and night blindness - Nyctalopia - then gradually limits to tunnel vision. In advanced cases, it can cause central vision loss as well. Visual symptoms usually start in teenage years, then progresses to the 4th or 5th decade of one’s life.
Thanks to our cellular visual heroes, we have the power to see the most minute details in broad daylight and the faintest of images under the darkest of night skies.