vision | Hearth Moon Rising

Jumping Spiders and Jellyfish Eyes

May 9, 2014

So inevitable was the development of vision among motile creatures that it has developed along two different evolutionary pathways: the brain in vertebrates and the epidermis in invertebrates. That’s right, the skin. Among the more primitive jellyfishes, the eyes are raised patches of cells, called eyespots. These eyes cannot form images but can detect the direction light is coming from. The surface of the entire jellyfish appears to be photosensitive, sensing light even when the eyespots are covered.

This is a Moon Jelly (Aurelia aurita). The primitive eyespots are along the edge of the creature, small protrusions where the rim puckers. Look closely. Photo by CarbonNYC.

While the vision of the jellyfish is limited, the octopus has eyes that can form images close up and at a distance, changing the focus of its lens by a combination of muscles and internal eye pressure. The octopus adjusts its pupil size for bright or dim light and can detect the direction scattered underwater light rays are traveling. Octopus vision is limited to the blue-green spectrum of light, which corresponds to the underwater environment, and octopus vision is less refined than that of vertebrates, allowing the creature to recognize filled shapes but not outlines. The octopus is an intelligent creature, capable of learning and detecting patterns, and so it is a favorite subject for research.

Starfish see from eyes at the bottoms of their feet. Photo Andre-Philippe D. Picard.

The invertebrate eye reaches its apotheosis in certain arthropods, and the Jumping Spider is a prime example. While Cave Spiders are completely blind and spiders who stay home on their webs have limited acuity, the hunting spiders have exceptional vision. The tiny Jumping Spider, only about a quarter of an inch in diameter, has four pairs of eyes, each with a specialized function. The large central forward facing pair has sharp vision within its limited field. The Jumping Spider has no lens to accommodate objects near and far, but the other eyes mitigate this problem to some extent. Another pair of forward facing eyes judges distance, and both pairs on either side of the head detect motion, with one of the side pair also having wide angle vision, giving the Jumping Spider the ability to see at almost 360°. If the Jumping Spider needs to see an object clearly, it jumps within range. Jumping Spiders have excellent color vision, seeing into the ultraviolet range. The hunting spiders communicate in courtship through visual cues, and another hunting spider, the Wolf Spider, waves his legs in code for the female, in a kind of spider semaphore.

A good view of Jumping Spider eyes. One of the peripheral pair is rudimentary and hard to see, but six of the eyes are clear. Photo Niky81.

If the invertebrate has a brain, the eyes do communicate with that brain, but the eyes of invertebrates are different from vertebrates in structure. Reflecting evolution from the epidermal tissues, invertebrate eyes connect to different parts of the brain, and more visual processing is done in the eye itself. Vertebrate eyes, as extensions of the brain, process more visual information in the brain. Invertebrates truly see the world in different way than humans.

Source

Sinclair, Sandra. How Animals See: Other Visions of Our World. New York: Facts on File, 1985.

Postscript

In the course of my research I discovered that “Jellyfish Eyes” is the name of a 2013 film by Takashi Murakami currently being screened at indie art theatres around the USA. I chose the title of this post before realizing this, as I was truly interested in actual jellyfish eyes. I may be the first to point out that the eyes on these “jellyfish” creatures are in no way anatomically correct. Alas, few sci-fi artists care about such things. Here is the trailer.

Ipnops

April 25, 2014

According to the literature Ipnops is the only vertebrate in which both the eyes and the optic nerves are completely missing. The present investigation has however shown, beyond doubt, that the peculiar organs on the head of Ipnops, which are generally held to be phosphorescent organs, are in reality modified eyes.–O. Munk. “The Eyes of Ipnops Murrayi”

Vision is important to nearly all animals, so much so that only animals who live in caves with no source of light are completely blind. Even bats, who rely primarily on echolocation for orienting themselves and finding prey, have some vision.

In the deepest depths of the ocean, where no light can penetrate, fish use a biological flashlight. Called bioluminescence, this cool light, usually in the blue-green spectrum, is manufactured by marine bacteria and resides in the gut of the fish. It is believed that the fish have some control over this light, which is used to hunt, lure prey, attract a mate, or aid in coordination of the school.

One of the strange fishes at the bottom of the sea is the ipnops. Like most bottom dwelling fish the ipnops’s eyes are on the top of its head, not on the sides, and these are round tubular eyes poking out of a flat head with transparent bones. Quoting from Wikipedia “The purpose of these structures is debated — they are light-sensitive and may serve to detect bioluminescent prey; it has also been proposed that the organs themselves may be luminescent and act as lures.” The ipnops lives in the very darkest regions of the sea, from the bathypelagic to the abyssopelagic or abyssal zone. Truly these animals reside in the abyss.

I have not had the occasion to use ipnops magically, but I think they may have some interesting, if specialized, applications. For one thing, “ipnops” sounds like a magical word. This would be a good animal to call on energetically when you find yourself “in so deep” that you cannot “see your way.”

Sources

Munk, O. “The Eyes of Ipnops Murrayi.” Copenhagen: Institute for Comparative Anatomy and Zoological Technique, 1878.

Sinclair, Sandra. How Animals See: Other Visions of Our World. New York: Facts on File, 1985.

Wikipedia, Ipnops.

http://media.eol.org/content/2009/05/19/16/68617_orig.jpg (Photo R. B. Reyes) Ipnops Agassizii

http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Ipnops.JPG/640px-Ipnops.JPG Ipnops Murrayi

Human and Animal Vision

April 18, 2014

It turns out that humans are highly anthropocentric in how we conceive of vision. The measures that we use tend to be areas where problems in human vision arise: focusing at distant and close range, seeing at night, depth perception, field of vision, and colorblindness. We don’t factor in things that most humans can do easily, such as recognize patterns, and we also don’t think about things we can’t do at all, such as recognize the source of diffuse light.

Here is a list of factors that vision entails (which may not be complete):

Ability to detect light (this is the core function of vision)

Ability to locate the source of diffuse light (polarization)

Ability to see in low light

Ability to see in bright light

Sensitivity to changes in contrast

Ability to see colors

Range of color vision

Ability to distinguish hues within a narrow band of color

Depth perception

Detection of movement

Ability to see stationary objects

Field of vision (including ability to see up and down as well as on a 360 degree plane)

Focusing ability (including speed of focus on near and far objects)

Ability to detect images at great distances

Clarity of vision at far and close range (accommodation)

Ability to detect shapes, both solid and outline

Ability to recognize patterns

Rapidity of image formation (analogous to frames per second in a camera)

Clarity of underwater vision

Ability to detect images below the surface of the water from above (and vice versa)

Ability to compensate for idiosyncrasies in refraction (closely related to the factor above)

Ability to compensate for movement (self locomotion as well as movement in the environment)

Formation of a single image versus split vision

Capacity for visual organs to withstand environmental challenges such as cold, pressure, and debris

I have not been able to find information comparing abilities to see and interpret auras.

So which animal has the best vision? I was a few chapters into this book before I realized what a silly question this is. Each animal has a type of vision perfectly adapted to its environmental niche. No eye or set of eyes can function in all areas extraordinarily well, because there are a few areas that are mutually exclusive and so it’s a choice between specialization or compromise. If I did have to pick the animal with the best vision, however, it would be any member of the ape family, including humans. No doubt many will not believe me and will dismiss this as more anthropocentricism. I say this because while there are animals who outperform us in every area of vision, except perhaps pattern recognition, our eyes function competently in a wide range of environments and circumstances. Our eyes do little that is spectacular but almost everything well. This is probably the main reason we have adapted to so many environments around the globe.

Source

Sinclair, Sandra. How Animals See: Other Visions of Our World. New York: Facts on File, 1985.

Photo credits: Eagle–Vtornet; Chimpanzee–Thomas Lersch

How Animals See

April 11, 2014

Most of us intuitively understand that other animals do not see the world the way we humans do, and we like to imagine how things look from their point of view. It turns out that the ways of seeing are more intricate and varied than we realize.

I am returning this week to a favorite topic of mine: vision. Over the next several weeks I will be sharing insights gleaned from my perusal of an out-of-print book, How Animals See: Other Visions of Our World, by Sandra Sinclair. This book examines eyesight in a wide range of creatures, from insects to mammals, sea dwellers to migrating birds.

I did not realize when I picked up this book how unique it is, really one-of-a-kind. Since it was published in 1985 the other books on the subject have been children’s books, which is par for the course. Books on the really interesting topics seem to be written for kids, not grownups. Lack of interest may not be the primary factor here, however. The subject matter is difficult, so much so that biologists and others who study in this area use words and concepts that most people have only a fuzzy understanding of. Sinclair spent years researching her material under the mentorship of Dr. Dean Yeager of The State University of New York College of Optometry, and Dr. Yaeger writes in his foreword that even he was forced to read outside his areas of expertise in order to assist with the project. This seems to be the kind of book that only a very bright journalist with generous assistance from experts could make comprehensible to the lay reader. Even so, I do not think I would have been able to understand this material had I not already read some basic books about human eyesight such as Relearning to See by Thomas Quackenbush, which I wrote about last year.

I have tried unsuccessfully to find a more up to date version of Sinclair’s work. I have found only two books that are close: a 2012 book called How Animals See the World: Comparative Behavior, Biology, and Evolution of Vision by Olga F. Lazareva et al and Animal Eyes by Michael F. Land and Dan-Eric Nilsson. The blurb at Goodreads boasts that How Animals See the World “…contains 26 chapters written by world-leading experts” and calls it “An exhaustive work in range and depth, … a valuable resource for advanced students and researchers in areas of cognitive psychology, perception and cognitive neuroscience, as well as researchers in the visual sciences.” Animal Eyes is billed by the publisher as “…a comparative account of all known types of eye in the animal kingdom, outlining their structure and function with an emphasis on the nature of the optical systems and the physical principles involved in image formation.” Both rather dense sounding texts assume a solid knowledge base in the visual sciences, which makes me appreciate Sinclair’s work all the more. I have to say, however, that I found even this book a stretch.

Over the next few months, look forward to juicy bits of trivia about some very weird ways of seeing.

Source

Sinclair, Sandra. How Anmals See: Other Visions of Our World. New York: Facts on File, 1985.

Seeing More Clearly

September 20, 2013

Many people compare the eyesight of humans unfavorably to that of other animals, but actually we are quite visual animals with the excellent eyesight that reflects this. True, we cannot see small objects from great distances like the Peregrine Falcon, we do not have the huge visual field of the owl, we do not have the hair trigger motion detection of the cat, we cannot see in two directions like the deer, we do not have the excellent low light vision of the fox, and we cannot discern the wide color spectrum of the parrot. What we do have is highly acute adaptable vision suitable for a variety of purposes. We can see well at night in low levels of light, yet our diurnal vision can detect a variety of color. We excel at tasks requiring close vision, yet we can focus on objects miles away. Our ability to detect motion, while not rivaling that of the cat, is something we rely upon. It is instinctive and natural for us to have a clear visual mapping of our surroundings at all times. In short, though we can take no prizes in any particular aspect of vision, we are competent in a variety of areas, which is in itself remarkable.

The core belief of natural vision is that it is natural for humans to have good vision, and poor vision occurs not through the passage of time or any particular activity, but through disease and, especially, poor vision habits. Poor vision is usually an acquired trait that requires practice. Improving eyesight occurs through understanding and utilizing good vision habits – not, as commonly believed, by practicing “eye exercises” a certain number of minutes per day. As one vision teacher explained to me, “I expect my students to practice no more and no less than twenty-four hours a day.”

When I first began exploring natural vision, I was advised that “The most important thing you can do is to throw away your glasses.” I was horrified. The Department of Motor Vehicles had decreed that I needed glasses in order to drive legally, and I wondered how I could negotiate a long list of situations without sharp vision. “Throw away your glasses in order to throw away your glasses” – like so much of natural vision it seemed counterintuitive. I had expected my eyesight to gradually improve, and in the course of this improvement to gradually dispose of my lenses or gradually lower the strength of the prescription.

I was unable to stop wearing glasses entirely right away, but I did begin driving less and using my lenses only in situations where they were essential (which turned out to be less frequently than I expected). I did nothing else at first to correct my vision, and I would estimate that it improved 80% over the course of a year or two through this step alone. In hindsight I understand that this was not entirely due to my eyes readjusting to focusing on their own. There were deeper psychological changes occurring that were also changing my perception. We see with our mind as well as our eyes. For one thing, I let go of the idea that my glasses were an essential part of me. I also became comfortable with the fact that vision is not static: it is clearer some days and foggier others. I let go of the idea that I must have sharp vision at all times, and paradoxically letting go of that need sharpened my vision. Most importantly, I stopped expecting my vision to naturally deteriorate with time and began trusting my eyes to continue serving me.

In future posts on this topic I will describe some key insights of good visual habits and how they apply to divination and inner vision. In the meantime, consider the implications of the idea that letting go of the need to see sharpens the vision.

Relearning to See

September 6, 2013

This isn’t so much a review of Thomas R. Quakenbush’s book Relearning to See, considered one of the best books explaining what is called the “Bates Method,” as it is an exploration of how the principles of natural vision have changed my thinking and my life. Although most people will elect to go the route of glasses and surgery to correct vision problems, and a few lucky people have perfect vision without considering the issue, I think these insights have implications beyond correcting eyesight, implications especially for the magical practitioner.

I first decided to use natural vision methods over twenty-five years ago, when I was at the Michigan Womyn’s Music Festival. I was camping out at the festival with several thousand women, and I rolled over my glasses in the tent while I was asleep, breaking them beyond repair. I was a day’s drive away from home, and my girlfriend did not know how to drive, so I had no idea how we would be able to get home. I was in a bit of a panic. In the end, some women scrounged up materials and pieced the glasses together so that they could stay on my nose long enough for the drive – but that was the turning point. I saw that my life was hanging by a thread, depending on these implements to interface with the world, and I vowed that I would find a way to emancipate myself from the tyranny of eyeglasses. I had never heard of “natural vision,” and I didn’t know anyone who had successfully thrown away their glasses, but I was determined to be free.

Looking back, I can see that it was no coincidence that my commitment to better vision began here, just as it was no coincidence that my vision problems started in my first year of college. That year I began complaining of headaches, and my mother made an appointment for me at the “Vision Clinic,” as it was misnamed. It should have been called the “Adjusts to Poor Vision Clinic.” Sure enough, my eyesight had deteriorated. The explanation given was that I was spending long hours hunched over books, often under the glaring light of the library, and this was putting a strain on my eyes. I don’t dispute this explanation, and William H. Bates himself says that eyestrain is a big culprit in poor vision, but this is a surface explanation, like saying your car got dented because something hit it. What happened?

College is a period of indoctrination as much as a period of learning. The biases, prejudices and imperatives of Western civilization bombard the young mind, as the institution struggles against itself to teach that mind how to think while dictating to it what to think. Especially for a woman, the incongruities are fierce. I took what amounted to a minor in English literature, and in all those classes read exactly one book written by a woman. The thing that bothers me most about that is that I didn’t “see” it. I majored in economics, and it was never mentioned that most wealth is in the hands of men and poverty disproportionately affects women. What bothers me now is that I didn’t “see” it. For a woman higher education is a period of great strain, one she survives by turning a blind eye, or at least a myopic one, to what is going on.

Since I had not been inured to wearing glasses at a young age, of course I hated them, and I only wore them when reading a textbook – something that should have been instructive. When I graduated from college and began working for a large corporation, I began needing higher prescription lenses to read it all, and eventually needed glasses even to drive.

Michigan provoked the turn around. This was in the earlier days of the festival, before the rise of organized attacks that changed the timbre of the music. I had to never been in a crowd of so many women. I had to never been in a large public gathering where men were completely absent. I realized with a shock that for many years, perhaps most of my life, I had lived in heightened alert against the threat of rape, both in and outside of my house. I had never reflected on this, never even noticed it, but the absence was startling. My body was conditioned to tighten at the sound of a low voice or a rustle of leaves – but then I would remember, “I am safe here.” This is what the early days of Michigan were like.

It was also at Michigan that I met my first witch, or at least the first witch who would talk to me. I had imposed myself once on a woman who was pointed out to me at a local coffee house, who admitted to being a witch. I asked her where I could learn how to fly on a broom, and she brushed me off. But at Michigan there were lots of witches. I took a tarot class taught by Daughters of the Moon designer Fiona Morgan. I remember nothing about the class except that I felt excited to catch a glimpse of some thing totally new. Something was shifting in me. Looking back I see that my fuzzy eyesight was the distortions of patriarchy and my eyeglasses were the coping mechanism that allowed me to function. I left Michigan determined not to throw away my coping mechanism, but to dispense with the need for it altogether. The clearer vision that ensued allowed me to penetrate the occult realms.

As often happens when I write a blog post, I have discovered that I have more to say than I thought I did. I will continue the topic of acquiring clear vision in another post.