Chapter 2. Biological Eye  Designs

Chapter 3. Eye
 Design Illustrations
A. Plant light sensing
1. Grass, simple vines, 
and stems
2. Flowers
B. Lower animal eyes
1. Flatworms
2. Clams and Scallops 
3. Nautilus
4. Shrimp
5. Crab
6. Octopus and 
   giant squid
7. Spiders
8. Scorpions
8. Brittle Star 
C. Insect eyes 
1. Bees
2. Dragonflies
3. Butterflies
4. Flies
5. Ants
6. Moths
7. Beetles
8. Wasp
D. Fish eyes 
1. Shark
2. Flounder
3. Four-eyed fish 
E. Amphibian eyes
1. Frog
2. Salamander
F. Reptile eyes
1. Boa constrictor 
2. Rattle snake
3. Lizard
4. Turtle
5. Crocodile and 
    alligators
G. Bird eyes
1. Eagles
2. Hummingbirds
3. Owls
4. Ostrich
5. Cormorants
H. Mammal eyes
1. Whales
2. Elephants
3. Lions, tigers, and 
   other cats
4. Monkeys
5. Rats and mice
6. Bats
7. Tarsier
I. Human eyes
1. Iris
2. Lens
3. Retina

Chapter 4. Eye 
 Reproduction

Chapter 5. Optical 
 Systems Design 

Chapter 6. The Eye Designer

Related Links

Appendix A - Slide Show & Conference Speech by Curt Deckert

Appendix B - Conference Speech by Curt Deckert

Appendix C - Comments From Our Readers

Appendix D - Panicked Evolutionists: The Stephen Meyer Controversy
 

 
 
 
 
 
 
 
 

EYE DESIGN BOOK
Chapter 3
Section I
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3. EYE DESIGN ILLUSTRATIONS
I. Human Eyes
     Man has one of the most remarkable vision systems in the world. The human eye's key features include a highly-corrected optical design, repeatable geometry of materials, control by the brain, processing of retina information, interfacing with the brain from six >different levels of sensor cells in the retina, color vision, compression of data going to the brain, and the highly specific material makeup and orientation which enable each eye to function and memory of scenes to take place. (Fig 3.57a from p. 292, The Eyes & Visual Optical Instruments, Cambridge Press 1997, by George Smith and David Atchison)  (Fig 3.56 from p. 21, Science and Medicine, J/F 2000, Retinal Transplantation by R. B. Aramant) 

Figure 3.56b Retina  Layers (Same as  Figs 1.7b & 3.60b) Figure 3.57a Human Eye Diagram

Figure 3.56a Levels of  Sensor Cells in the Retina

At maturity, adult human eyeballs are approximately 0.9 inch (24mm) in diameter and slightly flattened in the front and back. Each of its retina layers is unique. The outer fibrous layer encasing and protecting the eyeball consists of the cornea and the sclera. The front one-sixth of the fibrous layer is the transparent cornea, which functions as a correction lens to help bend incoming light onto the lens inside the eye to form a sharp high-resolution image on the retina. Then a fine membrane covers the cornea. The remaining fibrous  layer of the eye is a dense, tough, opaque coating visible as the white of the eye. Its outer layer contains blood vessels that produce a "blood-shot eye" when the eye is irritated. The middle layer of the eyeball is densely pigmented, well supplied with blood, and includes major complex structures. The innermost layer includes the retina. Internally, the eye consists of a front cavity filled with watery aqueous fluid. The rear cavity is filled with gel-like vitreous fluid. The internal pressure (the intra-ocular pressure) exerted by the fluid inside the eye supports the shape of the front cavity, while the fluid with the holding tissue holds the shape of the rear chamber. An irregular-shaped eyeball results in ineffective focusing of light onto the retina. One can be "near sighted" or "far sighted". Both conditions are corrected with glasses or contacts. These conditions can require spherical and/or cylindrical corrections.       Focusing problems can also come from muscles that control the eye. This condition is also correctable with contacts or glasses. Conditions such as "lazy eye" or "crossed eyes" require special means of correction. A model of the major components of the human eye are further detailed to illustrate the overall vision system in familiar terms. (Fig 3.57b-c adapted from 1999 Eye Poster from Anatomical Chart Co. Skokie, IL)

Figure 3.57b Human  Eye Diagram Figure 3.57c Human  Eye Diagram

1. Iris
      The iris is a circular, adjustable diaphragm with a central aperture (the pupil). It is located in the chamber behind the cornea. The iris gives the eye its color, which depends on the amount of pigment present. If the pigment is dense, the iris is brown. If there is little pigment, the iris is blue. In some cases there is no pigment at all, so the eye is light. Different pigments color eyes in various ways to create the eye colors you see, such as gray, green, etc. In bright light, the iris muscles constrict the pupil, thereby reducing the amount of light entering the eye. Conversely, the pupil enlarges in dim light, to increase the amount of incoming light allowed to go the retina. As light to the retina is reduced, the ability to see color decreases.
      The iris is the extension of a large, smooth muscle, which also connects to the lens via a number of suspensor ligaments. These muscles expand and contract to change the shape of the lens, to adjust the focus of images onto the retina. A thin membrane lying beyond the lens provides a light-tight environment inside the eye, thus preventing stray light from confusing or interfering with visual images on the retina. This is extremely important for clear high-contrast vision with good resolution or definition.
      The most frontal chamber of the eye, immediately behind the cornea and in front of the iris, contains a clear watery fluid that facilitates good vision. It helps to maintain eye shape, regulating the intra-ocular pressure, providing support for the internal structures, supplying nutrients to the lens and cornea, and disposing of the eye's metabolic waste. The rear chamber of the front cavity lies behind the iris and in front of the lens. It helps provide optical correction for the image on the retina. Some recent optical designs also use coupling fluids for increased efficiency and for better correction. (Fig 3.58a from p. 146, Iridology, Vol. 2, 1982, published by Jensen Enterprises, Escondido, CA 92027) (Fig 3.58b adapted from 1999 Eye Poster from Anatomical Chart Co. Skokie, IL) 

Figure 3.58a Human  Iris Mechanism

Figure 3.58b Human  Iris Mechanism

2. Lens
      The typical bi-convex (curving outward on both surfaces) lens is a crystal-clear, transparent optical element that is semi-solid and flexible. It is shaped like an elongated sphere. The entire surface of the lens is smooth and shiny, contains no blood vessels, and is encased in an elastic membrane. The lens is held in place by suspensor ligaments that can cause the lens to either fatten or become thin. Complex control systems automatically change its focal length to precisely focus light images on the retina according to where the brain is directing the eye to see. Many variations in human sight due to lens imperfections are now correctable to near perfect vision using new laser techniques, contact lenses, or conventional glasses.

3. Retina
      The retina is the innermost layer making up the eye optical path. It is a thin, delicate, extremely complex sensory tissue composed of six layers of light sensitive cells. The retina encircles the rear portion of the eye. Photoreceptor cells in the rods and cones convert light first to chemical energy and then electrical energy. Rods function in dim light, allowing limited night vision. Typically, rods are used to see the stars; rods do not detect color, but they do detect movements and fine detail. There are about 126 million rods in each eye and about 6 million cones. This compares to only 1 million sensors in more common digital cameras. Cones function best in bright light and allow color vision. Cones are most heavily concentrated in a tiny hollow in the rear part of the retina.

Dense fields of both rods and cones are found in a circular region surrounding this high-resolution area. Continuing outward, the cone density decreases and the ratio of rods to cones increases until both rods and cones disappear completely at the edges of the retina. This enables us to see much more detail over a limited field of view than most TV cameras are able to resolve.       The optic nerve connects the eye to the brain. Thousands of fibers of the optic nerve cells run from the surface of the retina and converge to exit the eye at the optic disc (or blind spot), an area about 0.06 in (1.5mm) in diameter located at the lower rear portion of the retina. The fibers of this nerve are made up of a large number of cells, each having thousands of connections to carry electrical impulses from the retina to the brain. If the optic nerve is severed, vision is permanently lost.        The human eye vision system preprocesses the six different levels of sensing in the retina in parallel before information goes to the brain for final processing. These six levels represent six different cell types that make up the retina sensor. Each sensor layer plays a different role in seeing and recognition. Compression of data from each of these layers of sensors results in considerable compression of key visual data going to the brain. This parallel processing allows a rapid means of recognition of complex information.        With optical help such as from telescopes, we can further explore our universe. Likewise, we use microscopes to see minute building blocks of eyes such as cells. In comparison with optical instruments, the angular coverage of natural eyes is typically wider than most film and video cameras that are used to record specific events. Our vision systems are an example of irreducible complexity not capable of creation by mutation and natural selection. (Figures 3.59b, 3.60a, and 3.61a from p. 136 and 137, Iridology, Vol. 2, 1982, published by Jensen Enterprises, Escondido, CA 92027) (Fig 3.59a, c and 3.60b adapted from 1999 Eye Poster from Anatomical Chart Co. Skokie, IL) (Figs 3.61b by permission of James T Fulton, Dir of Research Vision Concepts)

Figure 3.59a Human  Retina diagram Figure 3.59b Human  Retina diagram Figure 3.59c Human  Lens Section Figure 3.61b Retina  Sensor Pattern

Figure 3.60a Human  Retina diagram  for perspective  of rods and cones

Figure 3.60b  Retina Layers (Same as Figs  1.7b & 3.56b)

Figure 3.61a Human  Retina Rods and Cones

     Several people have researched image detection and processing technology found in nature with the idea of using it for new system development. Working toward a complete understanding of eyes is certainly a challenge. One article, LIFE LESSONS [click to download PDF file], written by Don Wolpert for the Feb. 2002 issue of OE Magazine, a SPIE publication, has some very interesting ideas. He has done considerable work in this area.
     For an intesting article by Peter W. V. Gurney on the retina, go to Is Our ‘Inverted' Retina Really ‘Bad Design'?