The next part of the puzzle is the way an image is created in our eye. Let’s use an analogy of a camera. What you need to understand is that the images we see don’t exist in the real world. What exists in the world is a chaotic mess of photons running around and bouncing off surfaces in any directions. So once the photon hits the eye, it is transmitted to the retina the same as light is transmitted to the film in a camera. Of course, the image is upside down, but we don’t see the world upside down, right?
Here comes to play an ingenious mechanism of an eye -> thalamus –> primary visual cortex combination that is responsible for what we see (there is one more thing called the inverse problem, so if you are interested, here is a link to that). Let’s look into that, so we have the whole picture of whats our vision about.
The Cornea is the first step into or understanding a vision. What it does is redirecting or refracting the light that’s flying around and pointing them in the right direction so it can form the image. You might think that is it the Lens that is doing that, but that’s not true.
A Lens‘ function is to make the light that goes into the eye (and through the Cornea) land precisely on the retina. Not in front and not behind.
The Ciliary muscles and Zonule Fibers are used to form the Lens into a shape that is best for landing the light exactly onto the retina.
And now let’s talk about the Retina. Not the Apple display but the actual retina in our eyes. It’s the visual sensitive part of the eye consisting of rods and cones. These tiny parts are responsible for transmitting information to the brain. The two types, however, do slightly different things. Cones are most densely located in the retina’s Fovea area, while rods are primarily located in the peripheral regions. Cones functioning very good in very bright circumstances, so they are used mainly by your eye in sunlight, indoor light and scarcely in the moonlight. On the other hand, Rods are very good in dark, starlight and moonlight.
Have you ever heard that you can not see color in the dark? That you have basically black and white vision? This is true, but it’s not because rods are less sensitive to light stimuli. It is because they can not see color. And since they are made for use in the dark, you can not see the colors as cones would. You also see more broadly since rod are well distributed around the peripheral parts of the retina.
Fovea is the region that we use to see with the greatest detail, it’s the part that has the most excellent sensitivity to detail in light and has the finest resolution (again, cones distribution). To get the light to land on the fovea we have to align our eyes, that the light goes straight onto that point.