h a l f b a k e r yJust add oughta.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Please log in.
Before you can vote, you need to register.
Please log in or create an account.
|
The architecture of the human eye, which, like all mammalian eyes, has the optic nerves from each retinal cell coming out in FRONT of the retina, not out from behind the retina. These numerous nerve fibers gather together at a single spot and plunge through the retinal wall, and the back of the eyeball,
en masse. There is a HOLE in our vision at the spot where that bundle of nerves goes through the retina, and this is known as "the blind spot". (Yes, the brain compensates somewhat for it, but it is there all the same, waiting to trip you up in accordance with Murphy's Law.)
Well, folks, it happens that the architecture of the octopus eye, derived from a different evolutionary lineage, has its optic nerves coming out of the back of each retinal cell. An octopus has no blind spot! Why not copy the genetic instructions for that design, for human advantage?
Another thing: I don't know how the nerves of the octopus eye get together (do they do it INSIDE or OUTSIDE the eyball?) to form the main optic bundle. One of the problems that a human eye is subject to is "retinal detachment". Well, if a retinal cell is attached to the wall of the eyeball, and it has that extra mass of the nerve filament in front it it, then that increases its ability to detach. But if the nerve comes out behind the retinal cell and goes through the eyeball wall, before joining all the rest, then that could constitute extra anchorage for a retinal cell! I would promote this design even if it wasn't quite the way an octopus eye is constructed.
Extra eyes have been suggested as one way to improve human vision, but I think it might be a bit difficult to manage properly (brain circuitry may need significant enhancement to handle the extra data input). An alternative is wider spacing of the eyes, but this is general characteristic of PREY animials, not predators like humans. Prey animals NEED near-360 vision to detect predators more easily. Meanwhile, predators need stereoscopic binocular vision to accurately estimate distance to the prey (close enough to dash or jump, yet?) The two traits are somewhat exclusive of each other, because wide-separated eyes don't overlap their views enough to allow good stereovision. Perhaps two wide-spaced eyes plus a third central eye (as a compromise with respect to anyone's desire for multiple eyes)? I dunno if I would like myself in a mirror, though, with three eyes. It'd take some getting used to it....
Sensitivity to additional bands of the spectrum has been suggested, and is a fairly good notion. There are practical limits, though, for at least two reasons. First is the question of where do the extra vision sensors get PUT in the retina? We have pretty high-resolution vision because retinal cells are small and packed tightly. Replacing one type of sensor for another will merely degrade the visual acuity associated with the first type. Nature has done that already, with respect to our monochrome and color vision sensors. The focal point of our vision is so well-packed with color-sensors that the monochrome sensors (which are 10,000 times more sensitive to light, and are primarily responsible for our night vision) are seriously lacking! Thus astronomers have to use their peripheral vision, during their night work with an eyeball telescope. There are plenty of monochrome sensors at the periphery of our vision.
Next, it is a fact that different substances have different tranparancies with respect to different frequencies of light. While the lens of the eye consists of the most transparent tissues in the body, the reference wavelengths are ordinary visible light. I don't know how transparent those tissues are to UV or infrared, and I certainly don't know how much room there is for improvement. Additional retinal receptors are to some extent readily available for imitating; many insects are sensitive to ultraviolet. And some snakes are directly sensitive to IR. To what extent we can re-engineer them for human advantage remains to be seen (no pun intended).
The absence of colour vision in cephalopods
http://www.google.c...bsence+colour&hl=en
...a series of
behavioural experiments has shown that octopuses cannot learn visual discriminations on the basis of hue under conditions in which they learn to make brightness discriminations. [-alx]
An argument for human eyes over octopus ones
http://www.catalase.com/retina.htm
Don't know about the validity of his claims, but it's plausible. [-alx, Aug 15 2001, last modified Oct 21 2004]
An argument for human eyes over octopus ones
http://www.catalase.com/retina.htm
Don't know about the validity of his claims, but it's plausible. [-alx, Aug 15 2001]
UV Sensitivity in Aphakic Subjects
http://starklab.slu.edu/humanUV.htm
Research by Dr William Stark [philmckraken, Oct 21 2004]
[link]
|
| |
Trilobite eyes had calcite lenses. Why? No other animal has ever grown eyes like that. Why not? |
|
| |
My blind spot's never done me any harm. Ever wondered why, in order to 'see' your blind spot, you have to cover up one eye? Yes, it's because the other one will fill in for you most of the rest of the time. The advantages in eliminating the blind spot are negligable. |
|
| |
Besides, octopuses are colourblind and very sensitive to light. Fine if you want to make a living underwater, but I'm happy foraging for fruit in the forest, thanks all the same. |
|
| |
Dog Ed, I suspect that part of the answer to your question concerns the rigidity of calcite. That implies fixed-focus lenses, while we need softer variable-focus lenses. |
|
| |
waugsqueke, please give the trilobites SOME credit, because they inhabited this planet for something like 250 million years, while we've only been here maybe 2.5 million years (counting certain pre-H.Sapiens ancestors). |
|
| |
-alx, a desire for an alternate design does not automatically mean that ALL the details of that alternate design are also desired. The ones I thought would be worthwhile enhancements were the ones I described. Obviously, when seeking enhancements from whatever source (UV receptors from bees, for example), we would not want any anti-enhancements that happen to accompany it (faceted eyes). Not to mention that I was under the impression that octopi are NOT color-blind, because some species can do the chameleon thing. |
|
| |
Regarding light sensitivity, it occurs to me that some improvement to the iris might be in order. I don't know that we would want slits like cats have, because that type of iris I suspect is associated with a less-clear visual image, but cats have it because so many are nocturnal, and that design allows extreme opening of the iris for light at night. Just some greater range in operability of our current iris design is in order, I think. |
|
| |
I question the assertion that faceted vision would be an
anti-enhancement. It depends on what you're going for. I
imagine some people would find it rather agreeable. |
|
| |
The problem with nicking genes encoding for as large as structure as an eye from other organisms and just inserting them is that you cannot (as is currently understood) just copy-paste certain characteristics, as these make up a tightly integrated (and overlapping) whole. Whilst it may not be problematic to add a gene for creating a specific protein, the ability to select & copy only those genes for octopus eyes which encode for the characteristics you want is a WIBNI. I am not arguing that humans have perfect eyes, just that the idea we can nab a few bits from an octopus is infeasible at best. |
|
| |
Whether octopuses have colour vision is a matter which is not yet settled. However, most recent studies have reached the conclusion that they are colourblind, and the idea has reached general (though not unanimous) acceptance. |
|
| |
Finally, since the word is from a Greek rather than Latin root, the plural is octopuses. |
|
| |
Calcite is a birefringent mineral, so trilobite eyes may have had a unique ability to see using polarized light. I agree with -alx that wholesale eyeball replacement is rather unlikely, but it might be possible to modify the protein used to build the lens so that it polarizes light, or has a higher refractive index (so that the lens doesn't have to deform as much to focus properly). |
|
| |
It was my understanding that while the genes mostly code for proteins, some of them (the "homeobox" genes) are in charge of overall body-parts configuration. Some of THOSE are the genes that need to be modified, to get the optic nerves on the underside of the retinal cells, or to create a greater-range iris, or to adjust the proportion of one kind of retinal cell to another, in any given region of the retina.. Some of the ordinary genes would have to be modified, to alter the properties of the retinal cells (such as to lose color vision, or to acquire UV and IR vision). |
|
| |
Obviously at this crude stage of our genetic engineering capabilities, it will be very difficult to precisely just a few genes in the desired way. But the precision of our tools generally increases with time, and so, eventually, we should be able to make only the improvements we want, without fear of messing other stuff up. Do note that the best supercomputers of today are just starting to be programmed to solve "protein folding" problems (one of the keys to understanding the consequences of messing with genes) -- and in twenty years the equivalent of those machines will probably be on your desktop. For example. |
|
| |
I just saw this at www.tomshardware.com, in the news area: |
|
| |
Wonders never cease in science and the sources for inspiration are apparently boundless....who would have imagined that chalk-like calcite crystals in the skeletons of marine creatures known as brittlestars would lead to better-designed optical elements for telecommunications networks. The surprising discovery that brittlestars use calcitic crystals to act as optical detectors, in addition to providing skeletal support, was made by an international team of researchers, including scientists from Bell Labs, the Weizmann Institute of Science in Israel and the Natural History Museum of Los Angeles County, and will be described in an article that will be published in the August 23rd issue of Nature. The scientists say the calcite crystals are nearly perfect optical microlenses that perform better than any we can manufacture today. |
|
| |
--------------------------------- |
|
| |
It should be noted that a major reason for using interchangeable lenses on cameras is that each lens is a rigid body. NO single camera lens is a flexible/adjustable thing like the lens of the eye. Possibly, if that range of flexibility and adjustability could be enhanced, telescopic and microscopic vision would be available. Possibly the only way to truly get vision enhanced like THAT is for the eye to incorporate two of its adjustable lenses, just like the first telescopes and microscopes. I suspect that seeing such eyes in a mirror would take some getting used to -- those first telescopes and microscopes had tubular separators between the lenses...the eyeball muscles would have to be stronger, to support such a structure! Getting rid of the eyelids, as suggested by waugsqueke, might become a necessary part of such an idea. As has been noted, there are always trade-offs...and personally, I'm not going to vote for it, at least in that design. An alternate design would be bigger eyeballs, with the second lens INSIDE the eyeball (the larger ball places the retina farther back from the current lens location, making room for the separation of the two lenses). |
|
| |
Mephista, about those "succeeding consequences" -- Please note that any genetic modifications done by genetic engineering can be undone by genetic engineering. REALLY deadly genetic mods usually manifest before birth (cause of most natural miscarriages is bad genes). |
|
| |
I'll go for it as long as I get some tentacles in place of hair (on my head).
aaaaah, I have made sure to annotate every single idea seen by my own eyes today. Been a year since I did that. |
|
| |
Evolution has provided a bit of an advantage regarding night vision in humans. Some humans are born with monochromatic vision, the lack or cones interfering with the function of rods allows these people improved night vision. The downside is of course being colorblind, truly colorblind. But it does result in substantially improved night vision. Myself, I am Blue Monochromatic (BCM) last that I heard there were 34 of us. What I am curious of is if achromatopsia provides any advantage regarding night vision, if so that might explain why those with it would be better at night fishing (Pingelap (island)). If anyone knows the answer I would hope they would share. |
|
| |
[Rats], this is place devoted as much to speculation as to fact. I do not know the facts you need. But I do know that there are so many variations from the theme of "normal human" that perhaps none of us is truly normal. Your particular situation sounds too rare to have had a lot of evolutionary value, if there are only 34 of you. For comparison, think about the vast numbers of people who have sickle-cell anemia, which happens to be associated with increased malaria resistance. Anemia, says Evolution, is better for humans than malaria. |
|
| |
Perhaps if a major shift of human activities occurred, such that we became more nocturnal than diurnal, then your traits could become quite valuable, Evolutionarily speaking. Perhaps there HAS BEEN a tribe of nocturnal humanity, and you are descended from them. |
|
| |
The retina of the human eye does have some sensitivity to UV light, as demonstrated by people with aphakia (no lens) - apparently with no ill-effects(see link). We cannot normally see UV because it's blocked by the lens. |
|
| |
Speculation is that evolution "chose" this lens material, as others "available" to evolution that are transparent to UV also have some chromatic aberration. |
|
| |
So it should be possible to replace the human eye lens with a synthetic one that meets those criteria... why one would do this is another matter. |
|
| |
(apologies for use of teleogical language regarding evolution; but you get the idea) |
|
| |