The main benefit with LEDs is it increases battery life.
At one time, they would have been illegal. Has the law changed or simply one of these things that are now tolerated, like kids driving powered vehicles in a public place?
I'd describe specs as a correction, not aid.
Sight correction has been around for a very long time. If it had adverse effects, I'm sure we'd have heard about it by now.
Basic sight correction is for distance. As we age, we loose the ability to focus, hence needing reading specs. No matter how good your vision was when young.
And if you need correction for distance, driving without using it is rather anti-social.
BTW, I'm pretty old. But with correction for distance have no problems reading everything on the dash. But do need additional magnification to read or use a computer.
I used to have one short sighted eye that was just right for the dashboard, and one that couldn't read the dashboard but could see everything outside the car clearly.
With the loss of the short sighted one, I couldn't see much of the instrumentation (speedo was OK). So now I have bifocals with the cutoff set to the top of the dashboard under normal driving conditions. The prescription for distance is very weak and corrects a recent, slight, age- related change.
Ready made reading specs have plus lenses. Various strengths. If you are hyperopic (your eyes focus beyond infinity) all you're doing is correcting that. Ready made may be OK for that provided both eyes are the same and you have no astigmatism. But given how cheap prescription ones are - and how important a regular eye check is for picking up problems (and not just with the eyes) makes little sense not to get them.
Scarey!
I can see a possibility for that, in that the eyes may not have to work so hard at the extremes and the muscles could lose condition and the ability to do so.
Even if that is not the case, using glasses all the time conditions you to expecting them and leaves you feeling that you are struggling without, whereas if you spend long periods without, you are used to it and don't struggle.
On a different point, a child with a "lazy" eye can use glasses to correct their vision for a few years. Using them for that period actually improves the ability of the eye with and without glasses and as they reach about 8 years, that improvement becomes permanent and they can choose whether or not to continue wearing them. If they do not wear the glasses in the first place or not for long enough, the brain learns to disregard the weak eye and it remains permanently weak.
In my case astigmatism means that I am partially shortsighted and partially longsighted and the combination means that I can do without glasses for most things - although I prefer to wear them when driving, but am legal to drive without if I unexpectedly had to for some reason.
SteveW
The muscles in a perfect eye are totally relaxed for distance vision. They operate to increase the power of the lens for close work. (That why an optician uses muscle relaxant drugs on a kid when doing a sight test.)
If you are hyperopic you have to use those muscles to focus on the distance. Hence not correcting that can lead to strain.
A combination of those muscles failing and the lens hardening means someone with otherwise perfect sight looses the ability to see close up with age.
An optician pal of mine joked that about 35 years was the true lifespan of man. Where they can still see in the distance for hunting, and repair their arrows etc at night. And in the case of women, bear children. ;-)
LEDs generally or flashing ones?
Flashing ones have been legal for 15 years now if they are of some minimal power figure and a suitable flash frequency.
GH
Socrates complained that writing lead to people not needing to remember things.
When I was first prescribed glasses for my short sightedness as an early teenager, the ophthalmologist did tell me that I shouldn't use them for reading. None of the other later ophthalmologist could see any point in that recommendation although I did find it more convenient to read without my glasses. I always used ophthalmologist in those days because that was what my parents thought was best, so they never had any financial incentive for what they recommended.
Will cycling do as an outdoor activity that I do with glasses - sometimes in heavy rain? :-)
I think these are 2.5's?
I've not been told I have that that I am aware of?
Slight but not enough to make individual lenses worth it (seemingly).
eg, Even with prescription glasses on my left eye is always just slightly weaker (focus) than my right. I think the issue is with the macular in my left eye, not the lens as such.
I have got them Dave, 3 pairs (one for each role, close-up working, std reading and long distance / driving) but find them less comfortable than the cheapo readers and overall, less convenient than just having the one pair that stay on my face all the time.
I did swap over to my soldering glasses earlier whilst soldering the wires directly onto a vehicle tracker PCB because the surface mount socket had been ripped off the board. Because it was soooo small, I really needed my bigger magnifier lamp but managed without.
Sitting in front of this 17" screen and closing my left eye it hardly makes any difference (still clear and sharp). Closing just my right eye and the text is still sharp as such but distorted slightly (and slightly darker). When I tried it last, the professionally made reading glasses weren't much better [1] ... and didn't fit as well.[2] ;-(
Cheers, T i m
[1] They might be slightly less scratched than these are now. ;-) [2] These Readyspecs stay on my head no matter what I'm doing (upside down etc) and being frameless (and with translucent arms) don't interfere with my peripheral vision at all.In article snipped-for-privacy@4ax.com, Dave W snipped-for-privacy@yahoo.co.uk> writes
When I look in the mirror of my Defender at night I can see the reflection in the rear door of the brake lights of the car in front. Haven't found a use for it yet though.
Flashing blue lights.
Why use a flashing torch if walking? You surely want to see where you are going, so a steady light is best. When walking if I see or hear something comming ahead I point the torch in that direction but dip it as I ould in a car once the oncoming vehicle appears to have acknowledged my presence.
I'm with Tim here. A lot of deterioration of sight is through lack of use of the accommodation muscles. While the lens does harden my sight deteriorate most when sedentary and focussed onto a screen with a blank wall behind. Since then I choose to sit where if I look over a monitor I have a distant view.
The worst killer for accommodation is varifocal lenses. The eye muscles become very lazy.
Err, someone with perfect vision will only choose to have reading specs when it becomes impossible to focus close enough without.
Why would you get varifocals if you still could accommodate OK?
Err, there is no such thing as 'perfect vision'. I'm sure many can read adequately without reading specs at all stages of life. The only issue is they might not be able to focus at distance without assistance.
Well, that discounts just about everyone in their later stages of life:
Perfect as in flawless. There is an accepted standard for this.
' Only if they start out with at least one eye 'short sighted'.
In which case their vision is flawed.
I presume short-sighted younger people (who still have working "focussing muscles" and lenses which obey those muscles) will have glasses which they wear all the time to correct a *systematic* error - eyeball too large (or is it too small) for the lens to focus at infinity. They *may* also be able to read without those glasses because their lens can focus at that distance without correction.
As people get older, their focussing muscles become weaker and/or their lens becomes stiffer and less able to change from its relaxed (infinity) setting to focus at a closer distance which requires the lens to be compressed diammetrically so it becomes thicker from front to back and so has a shorter focal length.
As you say, if one lens is short-sighted from an early age, it will be able to provide one-eyed close vision even when the other non-short-sighted eye can no longer change focus to see close up.
I've always wondered what eye surgeons do when they replace cataracts in both lenses? Do they set both eyes to a fixed infinity (and require the person to wear glasses to read) or do they set one to infinity and the other to much closer (so as to cover both close and distance in different eyes). Does the brain get used to discarding whichever eye's image is blurred and only use whichever eye is providing an in-focus image?
I don't know because my eyes have always had very similar focal lengths - for many years I was very slightly short-sighted and got a very small benefit from wearing weak distance glasses for driving. Now I'm in my fifties both eyes are losing their ability to focus to close distances so I need reading glasses; interestingly my distance glasses now actually make even distance less sharp than with my unaided eyes, and they definitely make my closer vision (eg of the dashboard) worse - so I've stopped wearing the distance glasses for driving. It's scary how my reading glasses used to be needed only when reading and made the computer screen more blurred than unaided, whereas now my eyes have changed further and my reading glasses are needed even for computer screen - and indeed with my reading glasses I can't focus as close as I could, so I probably need a new stronger prescription.
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