Discussion of the more technical aspects of eye anatomy, including the path of light through the eye--cornea, aqueous humor, lens, and vitreous humor, along with the amazing retina and how it functions--turns out to be tedious for a portion of our population. Their interest may extend only to maintaining eye health with proper care, including dietary practices promoting healthy vision, or how the eye examination may lead to a prescription for corrective lenses. When I visit the ophthalmologist, I sometimes apologize for asking many questions concerning eye function. Doctors in other specialties are also recipients of my “What? Why? How?” queries. Seldom are my requests dismissed. Medical professionals are humbly proud of their professional expertise. They are anxious to share their knowledge of the wonderful workings of their body system specialties.
Curiosity which surpasses our doctor’s office questions may be satisfied by in-depth personal searches. This material is available to laypersons in televised special programs, textbooks, magazines, or internet postings. My interest in more detailed scientific and medical information is driven by desire to share knowledge of the wonders of divine design features evident wherever we look. This blog expresses our conviction that science topics are a powerful apologetic for our Christian beliefs in the reality of God as Creator. The “Theology of Creation” is an under stressed topic in many churches. Here is a link to a previous post under that title:
Each medical specialty dealing with a body system or sub-system is rich with information about the Creator’s design features. The denial of plentiful supernatural design features of the human body appears to be a position of irrationality. This post closes with a brief discussion of the workings of the retina of the human eye. Perhaps it serves to inform readers how much more knowledge is available apart from knowing the familiar truth about rods and cones.
The retina serves to transmit point by point information from the outside world to rods and cones and neurons in the retina called ganglion cells. Each atom or molecule of objects in our visual field is the source of a point of light. One friend described visible objects in our external field of vision as “consisting of trillions of data points.” Separate data from these points fall on different parts of the retina, thanks to the precision optics of our eyes. The human retina receives a great abundance of information. 100 million rod cells and 5 million cone cells collect light information from the trillions of data points in our external world. We may agree that the information received by our retina exceeds information produced by our “pixel-rich” cameras and printers.
The energy of photons falling on our retinal rods and cones triggers the production of “all or none” action potentials--electrical impulses triggered in the neurons which lead from the rods and cones known as photoreceptors to other types of cells in the retina: (1) The “all or none” electrical impulses travel to cells in the retina termed bi-polar cells. All bipolar cells are neurons which, in turn, (2) transmit impulses to ganglion cells. Ganglion cells also occur in the retina. All messages then travel as action potentials from ganglion cells to centers in the brain for processing into a meaningful picture. This transfer of information occurs through the optic nerve. The optic nerves, in two sections, eventually terminate in brain centers. For review, we present this flow chart:
Photoreceptors (rods and cones) à bi-polar cells à ganglion cells à axons of the ganglion cells (the optic nerve) à brain centers.
The optic nerve consists of approximately one million nerve fibers carrying only “all or none” electrical impulses to the brain. Before the electrical impulses travel through the axons of the ganglion cells, two other types of cells in the retina, horizontal cells and amacrine cells, help integrate the information received from the rods and cones. They join with bi-polar and ganglion cells to accomplish the integration. This is information processing at an early level. The most extensive information processing and integration occurs in the brain.
Perhaps the information discussed, cursory as it is, arouses a generous portion of wonder, along with the desire to investigate these topics on your own. We trust readers recognize the futility of a naturalistic explanation for the thousands of wonders surrounding us at every level, both in the living world and the material cosmos. In the world of life, particularly human life, we must also consider the problems posed by the belief that naturalistic evolution, even theistically guided evolution, brought these wonders into existence.
