Why does the image projected onto the retina appear upside down?

The image projected onto the retina appears upside down because the eye’s optical system functions similarly to a convex lens. As light rays from the visual field enter the eye, they are refracted—or bent—by the cornea and the crystalline lens.12

This refraction occurs at four separate optical surfaces, causing the light rays to converge and focus on the retina. Due to the nature of this convergence, the resulting image is inverted. While the image on the retina is upside down, the brain processes these signals to interpret the visual world, ensuring that our perception of direction and space remains coherent.134