inverted retina

The human body is an astounding feat of engineering. Too bad the mechanics that work on them can talk to the designers.

Cheers

ina is built upside-down, with nerves and blood supply on top, and photo sensors b elow, against the back of the eyeball. "

We may never know, but I suggest that it might have to do with all the engi neering done here. Cost. Vision, at the level we have it, is considered a m iracle by those whounderstand it. Of course the rabble just takes it for gr anted. But those who know just how hard it is to do something like that do respect the engineering.

Of course that is your point, it saeems like the wrong way to do it but it was right for SOME reason. I share the desire to understand that reason. I suspect it has something to do with physiology and not engineering in the p aradigm we are used to.

mechanics that work on them can talk to the designers. "

Yes. Howevber like Scotty on the Enterprise, knew more about the ship than those who built her, and I assume that statement includes the designers. I odubt we will ever get to that point in understanding something like this.

But we can try.

I do have someone I can ask I think. Dunno if they got an answer but I will have to get their email address and, well, just ask. I also have something to send him.

The place is not far from him. He has a bunch of degrees and shit and has s tudied genetics and nutrition at least. Of course alot more. Now he's into IT at the moment. the kid is sharp and if anyone were to critique the desig n, he would love to do it.

And he might just want to take his Wife and Glock out to dinner at Shooer's restaurant in Rifle, Colorado. Since I planned to send him that pic, I wil l include the question.

Really, there has to be a rason for this. Your nerves are not on top of you r skin right ?

Tell you what, I am not erasing this post because of this, but I may have j ust figured it out.

The bloodstream supplies the aqueous humor, which is the fliud that inflate s the eyball and provides the proper refractive index for the whole dongle to work. If thoise capillaries, which ois what the veins and arteries actua lly are at that point, were to neve to excrete the proper components for th e aqueous humor, that would have to be done THROUGH the rods and cones. May be that's not so good, even though I am pretty sure they need similar nutri ents/feed.

Glaucoma is when there is too much pressure. If you do not want to smoke po t constantly, they install a pressure regulated drain in your eye. It is a little bit more than a cataract operation, but it is considered almost rout ine now.

Tell you what, when it comes to the maintenence of the body, I would rather go to a vet. Really. They are really better diagnostitians and practitione rs. However, there are certain things they do not do. Your dog is deaf or y our cat is blind ? Get your gun and a shovel.

But the thing is, if you applied veterinary principle to how you eat and so forth, in most of your life starting early, you can avoid alot of problems . And one of the things to do, believe it or not, is to stop listening to p eople who get richer when you get sicker.

ina is built upside-down, with nerves and blood supply on top, and photo se nsors below,against the back of the eyeball. I was just talking about that yesterday, at the Sausalito Cruising Club, with a young lady who recently h ad *two* detatchments, in both eyes. The inverted construction makes us hav e a blind spot, where all the connections fan out, and makes the retina les s well attached than it might be. Looks like it has its reasons.

That was the way the first one in the vertebrate line was put together, and it worked well enough that that's the construction that every vertebrate u ses. Cephalopods build their eye the right way around. We all use the same basic light-sensitive-protein-coding-genes, but the eye - as opposed to the light-sensitive eye-spot - has evolved repeatedly in different in differen t taxa.

The goo inside the main eyeball is vitreous humor. It's arguably a bad design because it's jello-like and can suck the retina off the back of your eyeball, if it shrinks in later life, or if you get a hard shock to the head.

I don't have vitreous humor in that eye any more. They slurped it out when they fixed my retina, and replaced it with pressurized freon... no nutrients there. Then, over about 2 months, my body refilled it with saline or some thin liquid. My color balance and focal distance changed some.

It's not a bad design. It is planned obsolescence. You need to consider that size *does* matter, the size of your telomeres. They shorten as you get older and everything in your body deteriorates. In the end you have to go to make room for the new models.

Yeah, there's not much that's funny about vitreous humor or vitreous humour.

They can talk. Too bad there's no chance of getting an answer.

Astounding, but full of faults too, which it mostly survives. Definitely not the work of anything approaching intelligence. For some features, I'd sack a junior mechanical engineer (like the fact that psoas has no antagonist, leading to most lower back problems. Fine for a quadruped, but we aren't).

Someone had to make that transparent joke. Should have kept a lid on it.

There are probably only so many combinations that can do the job of light and color detection. I will look at your link, but have not yet.

n they fixed my retina, and replaced it with pressurized freon... no nutrients the re. Then, over about 2 months, my body refilled it with saline or some thin liq uid. My color balance and focal distance changed some. "

Really.

One time a very long timme ago I changed the blue coolant in a three tube p rojection unit. The raster came out bigger, and I had to reset the converge ncee bigtime. It was because of the difference in refractive index of the l iquids becaus the system used (developed by Sony I think) used the coolant as an extreme concave lens which allowed the big lens on the outside(techni cal terms again) to collect a greater portion of the light emitted. It was a very important development.

But back to the subject, you had freon in ytour eye ?

Could you see at the time ?

And, what I really want to mention is that I got floaters really bad. I am probably a prime candidate for getting it replaced because it is so damn ba d I cannot read, even if my focus is corrected perfectly. If the floaters g et in the way of my fovea, oohh, it's macula now, in both eyes, I cannot re ad, nor see well enough to drive, or ride a bike and in some cases even to walk.

My retinae are not the worst I think. And I have been training my eyes to h andle outside. I was a big baby with the sunglasses and decisded this was n ot the way to go. I get used to it nad I think that right. Actually wearing sunglasses that do not block UV is worse than nothieng. If they darken the world and your iris' expand, they let in MORE UV than if you wore nothing.

Anyway, ost of the hemorage that caused this happened years ago when I was abusing myselfquite badly. Things are different now, I would not survive. t hing is, I can still function.

A job ? Well technicallly I do not need a job. I got these projects needs d one, and this little side gig doing high end vintge audio, plus I am sellin g off my junk and will be on eBay next week.

But anyway, what I menat to say is that I could not work a cash register. S eriously, with my eyesight I should not be charged with the conduction of r etail sales. And that pays minimum wage.

So how much does this replacement of the humor (what a word to use for that ...) COST ?

Yes. Basically it is good enough for us but definitely suboptimal.

The "Designer" had two choices and made the wrong choice for the mammalian eye! He got it right second attempt with the cephalopods.

Nasty. Hope the repair works OK.

Evolution is not related to engineering, because there is no designer, no plan, and no targets. (Actually, I have met some engineers that work like that...)

The result is never "optimal", nor minimal cost. There are never "good reasons" for the way a biological system is the way it is - it survives because it is good enough, and better (or luckier) than close alternatives. The gradual changes through trial-and-error and feedback move biological systems roughly towards local maxima, and occasional serious mutations lead to jumps around the genetic landscape which may lead to more dramatic changes. But for almost every aspect of every biological system, the "reason" for its "design" is merely "compatibility with the old design".

Thus we humans have ended up with eyes that have the retina on backwards, an optical system suited for use in water rather than air, a half-hearted attempt at colour vision (compared to our ancestors), and far fewer features than the eyes of birds, cephalopods, and crustaceans.

These are examples showing roughly what the eye /actually/ sees:

On the other hand, we have evolved a massively complex brain that takes the rough and limited optical information and re-creates a completely new picture inside our "minds". The plasticity of the brain meant that it evolved faster - evolutionary improvement of the human eye got outpaced by evolutionary improvement of the vision processing centre in the brain, and thus the survival incentive to improve the human eye faded away. (Compare this to animals with very small brains, which evolved better eyes.)

XXXX Yes, Bill is correct to point out the repeated re-evolution of the eye.

About the reverse structure of the retina, perhaps the barrier in front of the light-sensitive cells also serves to filter out the damaging UV - the ceph. under water don't have as much of this.

yeah, but on the bright side, no one needs them for very long.

Indeed he is.

This is highly unlikely. Such a large structural change (reverse or "correct" retina attachment) at a point in development when it would be relevant (i.e., when there is enough of a retina to form a UV barrier) would need a large number of serious genetic mutations, which is statistically almost impossible. The "reversed retina" arrangement was already stable in early fish eyes, long before the eye was taken out of the water.

My beef with the design is putting the pituitary gland near the optic nerve/optic nerve chiasm. A growth on the pituitary can cause visual problems. Here's a short pdf with info.

Yep. Last legal use for it maybe.

No. The refractive index was way off. As it filled, it was like looking through a porthole on a boat that was gradually sinking. Optically strange.

I've always had lots of floaters, only now they are different in the two eyes. Interesting, not a bother. There are specialized cells that are supppsed to prowl around in there and clean things up; I can see them in my repaired eye, looking like tiny tadpoles swimming around.

Doctors use lasers to bust up big swimmers; there are you-tube videos.

It's incredible to me that Darwinian evolution could produce something as complex as the eye, and then provide all sorts of contingency repair mechanisms, like the fluid refill and the cleanup cells.

It cost me about $300 total, which included a lot of office visits and two surgeries (cataract replacement, which caused the detach, then the repair.) And lots of follow-up lasering. Kaiser figured that the detach might have been their fault (it was) so cut the co-pays on a lot of the visits.

The article and links suggest that the inverted config, with active light pipes, is actually a good design.

Out of time sequence!

Everything is spot welded down now. They used lasers on me, cryo frozen spots on the young lady. That gives us lots of tiny blind spots, which aren't apparent.

Some people get lasered just as prevention against future detatches.

Looks like a bit of photon processing is needed/required so hence the inverted construction.

Recent article physorg:-

Andy

Maybe there is.

The results are usually astounding, not just good enough.