Darwin said, “the eye to this day gives me a cold shudder”. If that was true back then, if he had today’s knowledge of the eye he would be shaken down to his genes. A cursory glance at the scientific findings or our visual system reveals an organized complexity at all levels of resolution from millimeter to nanometer.
Take a close look at an eye. Between the object that I fix my gaze on and its sharp image cast onto one of my retinas there stands the cornea, aqueous humour, the iris and pupil, the lens, the vitreous humour
Precorneal tear film provides nutrients, lubrication for the cornea. It is antibacterial and removes debris while allowing light to pass through, refracted but virtually unrestricted. It isn’t a homologous film but consists of three layers, an outer lipid layer, an aqueous layer which supplies oxygen and nutrients to the cornea, and an inner layer of mucus.
Passing through this it then encounters the cornea and is again refracted, and then to the iris which control amount of light, onward through the lens which is adjusted by the ciliary muscles to focus the image at the retina.
From first entering the eye the light passes thorough a series of remarkable structures.
Corneal structure and transparency, by Keith M. Meek and Carlo Knupp, 2015:
The basic principles of corneal structure and transparency have been known for some time, but in recent years X-ray scattering and other methods have revealed that the details of this structure are far more complex than previously thought and that the intricacy of the arrangement of the collagenous lamellae provides the shape and the mechanical properties of the tissue.
If the remarkable structure of the cornea isn’t awe inspiring enough, then surely a glance at the retina will fill anyone with eye-popping astonishment. Not forgetting that retinas are living entities with life cycles that allow the whole to function as the parts are constantly being renewed.
I was inspired by comments in my previous thread to take a closer look at the visual system we share. Just a short time searching for info on this system has provided me with so much detail to add to my basic knowledge of the mechanisms involved. I think we could discuss this in more depth, share knowledge, and have an argument or two along the way. Sounds like fun to me and I’m sure I’ll learn a thing or two.
“Eyes are very cool”.
All in favor: eye!
The eyes have it!
As Everett Dirkson might have said, a billion years here and a billion years there and before you know it we’re talking real time.
Complexity is in the …eh… eye of the beholder 🙂
The retina is where light turns into nerve impulses. How those nerve impulses become visual experience in our minds/brains is I suspect unanswerable in the first person. Not that I’m saying anyone who thinks they can make a dent in it shouldn’t have a go
It’s no surprise
when it comes to eyes
That’s how it goes
They’ll top the nose
Below I’ve added an image taken from an image on Wikipedia of an image of a painting by Goya, which is an image of Saturn (Kronos) devouring his children, which is an ancient myth which engendered a mental image of time destroying the form which it had produced.
You’re a bright spark, Flint. 🙂 Meditate on this image and enlighten yourself about time which ultimately destroys form.
(I’ve been told that I bear a striking resemblance to Saturn as depicted by Goya. but I don’t see the likeness. I’m feeling peckish all of a sudden. What’ll I have for lunch? 😉 )
“O wad some Pow’r the giftie gie us
To see oursels as ithers see us!”
Complexity is in the physical eye of the beholder.
Knowledge of this complexity is in the mind’s eye of the beholder.
It is unanswerable by anyone who denies the reality of the spirit. The question is answered in the realization that the human consists of body, soul and spirit, and that spirit is not just some by-product of the body. Body and spirit are the two poles of our being. You trace the mechanism of vision from object to brain and then you are at a loss. This is understandable and logically consistent from your point of view. You envision a series of outer processes entering you from without, but even the neuronal activity is viewed from without. These are outer bodily processes.
But perception is a two way process. Through our inner spiritual nature we meet the physical in an outward direction. Our spirit moves out into the world. A mental picture is where the spirit meets the physical within the brain, an external perception is where the spiritual meets the physical out in nature.
I just recently learned that Irukandji, and other box jellyfish have up to eight eyes, some with corneas and pupils, and they don’t even have a brain.
But evolution also predicts this, because it is so. It predicts anything that is so.
Blue eyes are yet another demonstration of Goethe’s observation of light in front of darkness. The iris appears blue due to darkness of the posterior segment containing the vitreous humour lying behind the light filled area in front of the iris.
Another creature with eight eyes is the wolf spider. And their eyes are more like our eyes than the compound eyes of insects.
I’m tempted to look into what research has been done on the anatomy of these invertebrates.
Nope. The interface is when light is converted to nerve impulses in the retina. Developmentally speaking, the retinas are part of the brain.
Nope. I envision light falling on my retina (I only have one working retina) triggering nerve impulses that reconstruct those impulses into a perception of vision. How that works precisely, I have no idea.
Well, yes, in that we confirm the accuracy of our visual perception with feedback. I reach for the object I see and touch it.
If that works for you, fine. Makes no sense to me.
You only believe that you have vision because evolution favored those who believed they had vision. It doesn’t mean you actually have vision.
I’m talking about the act of seeing and the path of any supposed signal between the object and the observer, not the formation of the visual system.
Here Steiner talked about eye formation here
Here we see the polarity even in the formation of the eye. Peripheral cells form components of the eye, invagination to form the optic cup and the retinal cells developing and connecting with the brain to form the 2nd cranial nerves. The eye is formed through coordinated interactions, from within out and from the outside in.
Eye formation must be seen in the context of the whole.
That is what I said. Having no idea is equivalent to being at a loss.
If you have any concept of soul or spirit you no doubt regard these as aspects of the physical. But if body, soul and spirit each have their place within the human makeup and the latter two do not just emerge from the physical body then the relationship between the physical processes of perception and consciousness becomes less of a mystery.
If soul and spirit don’t emerge from the physical body, then how is the relationship between the neurophysiology and consciousness of perception any less a mystery? You’d still have the problem of causal interaction to deal with.
I’m not talking about bodily contact. My ego functions through the body, but, it is not confined to the body. I can become one with the object of my perception in a way that transcends space and time.
Yes, you’ve made that clear.
Such causal interactions within a person only become a problem when things are viewed as separate entities. But we are unified beings.
You would need to delve into the anthroposophical descriptions of the human being to come to any understanding of the connections between mind and body.
Here is a rough explanation as I see it. We consist of three aspects, body soul and spirit, but we can also be considered to have a sevenfold makeup, physical, etheric, astral, ego, spirit-self, life-spirit and spirit-man. All of these aspects are interconnected and are meaningless outwith the whole.
Rational thinking is the domain of the ego and any rational thinking I engage in will be accompanied by feelings which are connected to the astral principle, which in turn will disturb the etheric principle which as the formative principle will affect the physical body. Likewise if, say, I deliberately apply a tourniquet to my arm, this will have an effect on my etheric “body” and I will begin to feel “pins and needles” and a feeling of numbness. This feeling is associated with the astral principle.
The restriction of blood flow through my arm did not cause the disturbance of the etheric principle and then the pins and needles sensation. They were all aspect of the same process.
Looking at straightforward cause and effect, should be left to the field of physics or mechanics. It isn’t well suited to the study of life and consciousness.
Convergent evolution is commonly cited in discussions about the evolution of the eye. A common example is the comparison between cephalopod and vertebrate eyes.
Papers and articles such as the one in this link often appear.
Molecular Evidence for Convergence and Parallelism in Evolution of Complex Brains of Cephalopod Molluscs: Insights from Visual Systems
From the abstract they write:
And to finish they say:
Quite often similar forms are obtained using different materials and pathways. When we say cephalopods and vertebrates have convergently evolved camera eyes, this actually involves convergently developing protective skin coverings, corneas, pupils, lenses, retinas, optic nerves. Take a close look at individual eye development; from stem cells to the vast array of specialist cells of the visual system requires a great deal of coordinated activity from RNA splicing to cell migration.
From Scientific American
Another example of the convergent evolution of eyes is in the remarkable visual systems in arthropods.
From Convergent evolution of eye ultrastructure and divergent evolution of vision-mediated predatory behaviour in jumping spiders, by K. F. SU, R. MEIER, R. R. JACKSON, D. P. HARLAND, D. LI.
So animals invented the telescope millions of years before humans got round to it. 🙂