L S of USA asks...
Why does the human eyeball see the image upside down and turned it around.
In the case of the eye, the image formed in the retina upside down "travels" through the optic nerve to the parts of the brain where visual information is processed and where perception occurs. This, according to the experience of the reality that the other senses have given us since birth, shows us the image already perceived as right. That is, we do not see with the eyes but with the brain. Proof of this is an experiment in which subjects were placed some special glasses that inverted the images, after a certain time of taking them without taking them off they returned to see the world to the right, seeing it inverted again when taking them off.
Samuel Serna Otalváro, 2019 OSA Ambassador, USA/France
Vision is a very complex process, where the visual system transforms light stimuli into information that is processed by the brain. The eyeball acts as an optical instrument, a camera: light coming from an object is first focused by the eye’s optics (cornea and crystalline lens) to form an image on the retina, which detects photons of light, sample the light distribution, that later is absorbed and converted into chemical and electrical signals (visual signals) by the retinal layers. These signals exit the eye via the optic nerve and are transformed into cortical representations in the brain.
The information reaching the retina is upside down, because the process of refraction through a convex lens, the eye’s optics is around 60 D, causes the image to be flipped. But at the same time, the same optics allows to adjust extraordinarily to changes in the illumination, color, contrast, as well as having a large field of view, that with other optical design will not be possible. So, yes the image is upside down for a reason! But we do not see the world upside down…and the brain is responsible for that. We don't see images with our eyes. We see images with our brain. Essentially, the brain takes the raw, inverted data and turns it into a coherent, right-side-up image, thanks to its ability to adapt the sensory information it receives and make it fit with what it already knows.
Maria Vinas, 2019 OSA Ambassador, Spain