The Inner Workings and Astonishing Anatomy of Human Eyes Revealed
The human eye, a marvel of nature, is more than just a window to the world. It operates with a complexity that surpasses many modern cameras, making it a remarkable piece of biological engineering.
At the heart of our vision lies the optic nerve, a thick bundle of nerve fibres carrying signals between each eye and the brain. A key component in this process is the pupil, a gap that lets light pass through to the back of the eye.
The resolution of the human eye is roughly equivalent to a 14K camera sensor overall, but this is spatially non-uniform. The highest acuity, around 3K resolution, is concentrated in the fovea, the central focal point. This high resolution is due to the approximately 199,000 cones per square millimeter found in the fovea, a pixel density about 7.5 times higher than a top-tier digital sensor like the RED Gemini. However, this resolution drops off sharply outside the fovea, unlike cameras that capture the entire frame uniformly.
In terms of color perception, human eyes are highly sensitive and can rapidly detect color differences and saliency through specialized photoreceptor cells called cones. Humans have specialized cone cells tuned mainly to red, green, and blue wavelengths, enabling rich color discrimination and rapid color-based attention. This allows us to instantly spot a red object among grayscale distractors.
Our brains blend together the inputs from the previous 10-15 seconds, providing a smooth visual experience. Most people are thought to be able to discriminate around 10 million different shades using these three types of cone cells.
As we age, our lenses become less flexible, making it harder to focus close-up, often leading to the need for reading glasses in our 40s and 50s. Age-related conditions like glaucoma, macular degeneration, and cataracts are leading causes of blindness.
The retina, the innermost layer of the eye, is packed with light-sensitive cells and nerve cells. The rods, responsible for peripheral vision, work in low light, while the cones, which provide the details at the center of our vision, require bright light and provide color vision.
The human eye can process visual information with a temporal resolution up to about 75 frames per second typically, and potentially recognize flicker beyond 200 fps. However, perceptual stutter is generally unnoticeable beyond ~56 fps.
The human eye can adapt over a very high dynamic range, allowing vision from starlight to bright sunlight. This exceeds most camera and display dynamic ranges, although some advanced sensors approach high dynamic range capabilities.
Despite these incredible abilities, the human eye is not perfect. For instance, eye colour in humans is influenced by at least 61 genes, making it not straightforward to predict the eye colour of a child born to two blue-eyed parents. Additionally, dogs can see in colour, but they see mostly yellows and blues, and have fewer types of cone cells for colour vision compared to humans.
In conclusion, while the human eye outperforms most cameras in effective resolution when integrating the full visual field and in color sensitivity and dynamic adaptation under natural conditions, cameras offer uniform resolution and instantaneous capture that differs fundamentally from biological vision mechanisms.
- The complexity of the human eye, as a marvel of nature, is such that it rivals the functions of advanced science, making research into replicating or enhancing these capabilities in medical-conditions a key area of health-and-wellness and science.
- The human eye's high resolution and color sensitivity, particularly in the fovea, where approximately 199,000 cones per square millimeter are found, make it a marvel of eye-health, surpassing the pixel density of top-tier digital sensors.
- Despite the human eye's incredible adaptation abilities to a wide dynamic range of light, age-related medical-conditions such as glaucoma, macular degeneration, and cataracts can limit our vision and become leading causes of blindness, highlighting the need for continued science and health-and-wellness research.
