A Geometric Optical Analysis of Human Retinal Cells and the Hypothesis of Monocular Stereoscopic Vision

We propose a geometric optical model that describes real-image formation via monocular vision in three dimensions. We only assume that the ganglion cell nuclei, bipolar cell nuclei, and photoreceptor cell nuclei in the human retina can be treated as microlenses and actively participate in imaging. In particular, we suggest that monocular vision operates via an array of high-magnification micro-real-image telescopes oriented in various azimuthal directions. The main elements of each telescope are the following. The first is the cornea and crystalline lens, which serve as objective lenses with tunable focal lengths. The second is a paired array of ganglion cell nuclei and bipolar cell nuclei, which act as a conjugate mirror. The third is an individual photoreceptor cell nuclei (cone or rod nuclei), which function as a micro-eyepiece. The fourth is the outer segment of each photoreceptor cell, which serves as a micro-object-distance sensor. We also hypothesize that six combinations of conjugate mirrors and micro-eyepiece arrays work within the human eye. Each combination is responsible for perceiving different ranges of object distances. We further hypothesize that the process by which one human eye perceives object distances involves two stages: from near to finite distances, and from finite distances to infinite distances. In different stages, the distance between different optical elements is tuned so that the object distance can be computed a specific formula when the photocurrent at the retina photoreceptors outer segment layer vanishes. Lastly, we conduct computational simulations. We find that there are two possible processes. By tuning the distances between the elements of our optical model, the eye can perceive object distances as close as 25 cm to dozens of meters in one process and dozens of meters to kilometers in the other process, depending on the sensitivity of the eye to small changes in focal plane spacing.