Photonic waves bounce off objects willy-nilly based upon the ability of individual objects to absorb light or allow its escape. Refracted photons stray into the eyes. In humans, a dilating iris controls how much light passes through the pupil.
The incoming spray of photons are bent by the lens and strangely splayed on the retina. Before being absorbed by the rods and cones that convey the message which light has to offer, photons must first pass through nerve tissues that partly block incoming light patterns before doing their job as signal transmitters.
To facilitate peripheral vision and afford the ability to see objects larger than the pupil, the light patterns put on the retina are upside-down and reversed from how they entered the eye. Without reversal, the view of the world would be like looking through a drinking straw.
Stimulated by coherent light energy, neurons on the optic nerve disc pass their excitement to the brain. By this time, the incoming photonic pattern has been translated into chemical signatures that supposedly magically convey the precise spatial arrangement and atomic intensity of the light that breached the eyeball. Thus, luminous spectral input is transmitted to the mind-brain. But this is just the beginning of visual discombobulation. The optic nerve bundle from each eye crosses over to the opposite side of the brain at a crossing called the optic chiasma.
The visual cortex is at the back of the brain. Each hemisphere of the brain receives optical input from the eye on the opposite side of the head. The input images are mysteriously reoriented, mixing them together into a single mental image.
Once the chemical ferment from the retina reaches the visual processing part of the brain, a stunningly accurate facsimile of the received light pattern is painted by the mind in less than 150 milliseconds. In the process, the extreme distortion created by the eye’s lens is eliminated. Many other corrections must transpire to attain a discernable image with the clarity we associate with sight.