Where are all the blind people?

[binaryhermit]

Eh, for the most part much of Chicago's not *that* bad.
Then again, I might be oblivious to things.

[crich70]

People used to say that sitting too close to a TV screen (in the old tube tv days) was bad for you too. And there is the possibility of sleeping problems from bright screens at night. I haven't really noticed an inability to sleep though.

[crich70]

Originally Posted by Ripplinger

After reading all the links and reading about this topic for many years, I'm really thinking the current decline in kids' vision is more to do with them not being outside as much. Your eye muscles are constantly being used to change focus... indoors how much distance are you changing, 20' at the most? That's not very much. But outdoors your muscles really get a better workout viewing objects miles away and not just the next wall.

I think too much screen time might make your eyes feel tired, LCDs vs eink vs paper might make some not sleep as well (although neither have ever bothered me and I've had bad eyesight all my life, I'm very farsighted). I don't believe using your eyes to read a lot makes you blind or even causes any eye disease no matter what medium you read from, book or screen.

Not to mention kids these days get a lot more junk in their diet than we did back in the day. They talk about vitamin enriched foods but at the same time the amount of sugar, salt and bad fats in foods today has to have an impact on a person as a whole. Certainly it doesn't help prevent diabetes which can and often does affect the eyes as much as anything.

[theducks]

Originally Posted by Ripplinger

I agree, there are many reasons kids just aren't outdoors as much today, it can't be blamed any one thing. But as someone who lived in Chicago most of my life, in my case it was definitely real crime rates, not just an irrational safety fear.

Good point. (and that applies to us oldsters too)
I spend most of my time near my monitors or my Kobo these days. One eye is now pointing off in Left Field.
I used to spend weekends outdoors, up in the air or blasting down the slopes and I had no problems seeing (I also wore dark glasses because of glare)

[theducks]

Originally Posted by crich70

Not to mention kids these days get a lot more junk in their diet than we did back in the day. They talk about vitamin enriched foods but at the same time the amount of sugar, salt and bad fats in foods today has to have an impact on a person as a whole. Certainly it doesn't help prevent diabetes which can and often does affect the eyes as much as anything.

Wot?
I used to drink gallons of Kool Aid and munch Mom's cookies that were made with real butter. My morning Wheaties had Whole Milk and brown sugar or it was Bacon and Eggs.

[Frenzie]

Originally Posted by theducks

Wot?
I used to drink gallons of Kool Aid and munch Mom's cookies that were made with real butter. My morning Wheaties had Whole Milk and brown sugar or it was Bacon and Eggs.

Whole milk and bacon and eggs aren't bad fats.

[crich70]

Originally Posted by Frenzie

Whole milk and bacon and eggs aren't bad fats.

Not to mention that the amount of sugar in Kool Aid was probably relatively small compared to the amount of sugar in say Mountain Dew soda pop. (At least 45 grams per can). And back in the day mother's kept a watch on the kids to make sure they ate right, but now with many homes with either a single (working) parent or with two parents (that both work) kids lack that supervision in many cases. Why else has the incidence of Diabetes gone up so much these days? Of course without good nutrition kids have trouble concentrating enough to comprehend what they read anyway.

[AnotherCat]

Eat lotsa carrots for eyes "they" say .

There is just the two of us at home these days and we seem to get through lots of them. Not for any particular health reason, we just like them.

One trip through the supermarket checkout the operator asked, quite seriously, if we had a horse .

[Quoth]

Originally Posted by AnotherCat

Eat lotsa carrots for eyes "they" say

Which was WWII UK propaganda to attempt to hide that they actually had Radar on the aircraft!
Eventually the Germans duplicated the magnetrons (now the source in ALL microwave ovens as well as most Radar) even though the unit had explosive charge to destroy it when the aircraft would be shot down.
They are a simple to make device the Victorians could have made. The modern ones in a microwave are simpler. I have one out of an oven and I used to have a 1948 model. See Wikipedia.

It's true you'd be ill without any of the vitamins in carrots. BTW, carrots used to be almost white.

[AnotherCat]

Originally Posted by FrustratedReader

Which was WWII UK propaganda to attempt to hide that they actually had Radar on the aircraft!
Eventually the Germans duplicated the magnetrons (now the source in ALL microwave ovens as well as most Radar) even though the unit had explosive charge to destroy it when the aircraft would be shot down.
They are a simple to make device the Victorians could have made. The modern ones in a microwave are simpler. I have one out of an oven and I used to have a 1948 model. See Wikipedia.

It's true you'd be ill without any of the vitamins in carrots. BTW, carrots used to be almost white.

I had an elderly good English friend, long deceased now, who worked on the development of the high powered cm band magnetrons in the UK during the second world war. I have been involved in radio all my life and provided management services to or project managed a number of big military and civil radar projects in several countries.

And this going blind stuff can get people uptight and imaginations fired up when radars are involved. One secondary radar site was on a hill hill up above nearest houses a mile or so away below and they had a reputation of putting environmental claims in the way of any developments in the area. They got all uptight so I had the task of talking to them about it pointing out how secondary radar works, its very low power, etc. Fortunately one of the residents was an old retired physics professor from the local university and he came up to me afterwards to thank me for coming and went on to say that he had worked in the UK in radar during WW2 and they used to set dry grass on fire in front of the antennas (so would have been the early long wavelength ones, I assume).

I got one of the many surprises of my life decades ago during my first working visits to the USA to see signs on company cafeterias doors warning that there were operating microwave ovens inside - no wonder USA residents are all wearing glasses as I assume they still go inside their work cafeterias despite the frightening warning signs on the doors .

[Quoth]

It's only staring into the waveguide that gives you cataracts on radar. Though certainly you'd not want to stand on a step ladder in front of the dish if the motor drive failed and the magnetron kept going.

Microwave ovens are super safe if the door works.

Biggest risk with travelling wave tube based microwave links was the frightening power supply in the shack under the mast.

Some secondary radar doesn't emit ANY signals, it's receiving only the reflections of pulses from main radar elsewhere.
Also the inverse square law suggests setting grass on fire is apocryphal. The most powerful radar won't even warm the grass 5 meters away. It's also a focused beam, so there is almost no signal below the dish.

I qualified originally as an RF Communications engineer before changing to computer programming.

[AnotherCat]

Originally Posted by FrustratedReader

...It's also a focused beam, so there is almost no signal below the dish...

There are no dishes for HF radar
(and HF pattern is dependent on ground effect, and as they were out over the sea and short range they may have been LF so ground wave propagation - but Chain Home itself was HF -, in both cases important radiation and electrical connectivity at ground level.)

Regarding fires, I just listened to him as it wasn't the place to enter into discussions with activists present. I don't know what HF radars he was involved with but the Chain Home ones were HF and up to around 1MW, pulsed, fixed direction, I assume during development there may have been more power, recent OTH ones that I know of are up to 10MW. I took it that he could have meant anything, including from through air arc-overs at ground level connections, transmission line faults, etc.

I still hear various high power OTH HF radars around, the closest is around several thousand miles from me, that around 0.5MW so not very powerful as far as OTHR is concerned, but pattern not in my direction even for long path.

The secondary radars I have been involved with have been IFF/SSR types, so both TX and RX for interrogation of target. Have never, personally, come across any secondary radar that is RX only.

As I haven't been blinded by radar talking experiences is getting away from the thread topic so that is all from me on it.

[frahse]

Originally Posted by fjtorres

The only proven physical impact of screen viewing is eyestrain from the extended fixed focus of the eyes, which is why breaks are recommended to allow the eye muscles to reset. The same effect comes from extended longer distance focus (i.e., driving). Both are temporary. Lighting type has nothing to do with it. Lighting intensity has some effect.

https://www.mayoclinic.org/diseases-...s/syc-20372397

I saw an article that said that someone had come up with data that showed that cell phones had caused about a 35% increase in vision accommodation problems, mostly nearsightedness.

I don't know what the baselines were (before cell phones became so popular) or what age groups they were talking about. I don't recall the article saying much about that.

[meeera]

Originally Posted by frahse

I saw an article that said that someone had come up with data that showed that cell phones had caused about a 35% increase in vision accommodation problems, mostly nearsightedness.

I don't know what the baselines were (before cell phones became so popular) or what age groups they were talking about. I don't recall the article saying much about that.

If you go back to the cites I posted, this remains somewhat controversial, but the one environmental factor that seems to correlate better than any other with myopia - better than smartphone or device use - is time spent outdoors (with increased outdoor time being protective).

[John F]

Originally Posted by AnotherCat

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