Spectacle optics.
Do we have an optician amongst us who can answer the question posed here.
It involves the optician's definition of ADD. Is that strictly a mathematical one
or does it mean something else?
Here is the question:
The following is a bi-focal prescription for glasses.
1 and 2 are for the right and left eyes respectively.
1). . . . . . . Sph. . . . Cyl. . . Axis
Distance -2.5 . . . -2.75 . . . 100
Near. . . . +0.75 . . . -2.75 . . .100
2). . . . . . . Sph. . . . Cyl. . . . Axis
Distance -0.25 . . . -150 . . . 90
Near. . . +3.00 . . . -150 . . .90
Question:
If only a pair of reading glasses are required.
What figures are to be used?
Would these be the correct ones?
1R). . . . . Sph. . . . Cyl. . . ' Axis
Near. . . . -1.75 . . . -5.50 . . . 100
2R). . . . . Sph. . . . Cyl. . . . Axis
Near. . . +2.75 . . . -300 . . . 90
No guesses please. Or alternative approaches.
Just a correct answer.
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Upps. In using dots to get the compiled layout right, some figures lost their decimal point.
1). . . . . . . Sph. . . . Cyl. . . Axis
Distance -2.5 . . . -2.75 . . . 100
Near. . . . +0.75 . . . -2.75 . . .100
2). . . . . . . Sph. . . . Cyl. . . . Axis
Distance -0.25 . . . -1.50 . . . 90
Near. . . +3.00 . . . -1.50 . . .90
Question:
If only a pair of reading glasses are required.
What figures are to be used?
Would these be the correct ones?
1R). . . . . Sph. . . . Cyl. . . ' Axis
Near. . . . -1.75 . . . -5.50 . . . 100
2R). . . . . Sph. . . . Cyl. . . . Axis
Near. . . +2.75 . . . -3.00 . . . 90
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You could add them up.
42
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Douglas Adams favourite number?
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Please don't buy spectacles online.
Opticians on the high street are expensive but they will fit them properly, cutting the lens so that the central focal point lines up with your pupil. Online sellers are unable to do this, making their products inferior.
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>> Please don't buy spectacles online.
>> Opticians on the high street are expensive but they will fit them properly, cutting the lens so that the central focal point lines up with your pupil. Online sellers are unable to do this, making their products inferior. >>
There has been no mention of buying on-line. Secondly, not all high street opticians are responsible for the production of their glasses, entrusting them to specialist services.
I have friends who use to do such lens production and frames assembly after serving their time in the optical trade but, eventually, they realised they were doing all the work and the high street opticians were the ones making the big bucks at their expense.
As a result, they opened their own retail outlet as well and still charge much less for the finished, high quality products. All that is required (apart from choice of frames) are the results of an eye test.
Last edited by: Stuartli on Thu 11 Aug 16 at 19:22
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>> Please don't buy spectacles online.
>>
>> Opticians on the high street are expensive but they will fit them properly, cutting the
>> lens so that the central focal point lines up with your pupil. Online sellers are
>> unable to do this, making their products inferior.
>>
>>
>>
Opticians measure the distance between your pupils centre to centre to line up the focal points. You can do that yourself in front of a mirror or get someone to do it for you. I'm waiting for a pair from my local opticians for which I paid £123 but I'm ordering a spare set and two pair of reading glasses online at £12.50 a pop. Not much to lose if they are no good but no reason they shouldn't be and most if not all onliners will accept them back if they are no good.
I believe there have been several threads here where various online retailers were recommended by satisfied customers.
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I very much doubt that there are many now making their own lenses. And I am still smarting at being charged £300, about 3 years ago, for two pair, by a well known, once respected, name. I said I need to check that price elsewhere -- "come back if you find a better price" was the retort. In the end, partly feeling sorry for the guy who tested me and took me to the sales 'lady', and not wanting to use any more of my time, I paid up. But not any more.
I subtracted to get my answer above. It is just that it would be £45 to test my competence by buying a pair. Also, as I had an eye test last march, I guess not another free bee test available for a while. Shortly after I had my cataracts replaced.
What I actually wanted to do is more venturesome, write my own lens spec. By sheer fluke, on my new-old glasses, one near lens is superb for distance, with both eyes, and one reading lens is suitable for both eyes. Having specified a new distance part, the new addition to make that into a reading one (bifocals) is different from that used on the original distance one. I have done all the calculations, but am a bit wary of putting my money where . . ..
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>>www.glassesdirect.co.uk/
Ring them using the telephone number. I'm sure they'll tell you exactly how to do it.
Re Pupillary Distance, you can measure it yourself, or you can send them an old pair of specs previously fitted by an optician.
Or go for a free test - Specsavers often have offers on.
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Attracted by the low price and choice of frames, I once bought a pair of specs online, measuring my unusually wide pupillary distance with great care.
When they arrived they were useless. It seemed my PD was outside their sodding 'norms' so they just didn't believe it. Arrogant fools who imagine they are almost doctors... They wouldn't take them back or refund the money. Tchah raaaaas...
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Having now read more scripts on the subject, it is simpler than I thought.
My take on it is: The distance lens (first line) corrects for the eye sight errors --- as your would expect. Then, to create a reading (near sight) lens on part of it, you add a suitable magnifying glass (plastic) on top of the existing one. That additional lens ranges from about +0.75 up to a maximum of +3.50 (and is always +ve) as limited by the original plastic thickness, before starting to machine it. If you look closely at a pair of specs, you can see it is on top. The cyl lens and angle, on the 2nd line, are just a repeat of what is being used for the (distant) lens on which it sits. The cyl, when -ve, is not round as it has to be concave like.
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One of the earpieces of my distance specs came off and I couldn't find the very small screw. Went through yesterday with them balanced on my nose, but of course they kept falling off at inconvenient moments, a dangerous distraction when driving. I have a very small screwdriver but it wasn't small enough to undo the screws of my mother's old glasses for an attempted repair.
My own glasses are very good specs, with a coating on the outside that darkens as the outside light intensifies. The lenses are plastic, unbreakable of course but more importantly extremely resistant to scratches and scuffs. They are still unmarked after several years of careless use, being trampled in gravel and so on.
The optician in a nearby town provided another screw and I don't think charged for it (opticians can be surprisingly expensive). I had spent a lot of last night having semi-nightmares about the glasses, tossing and turning, half-awake, terrible spectacle anxiety, lenses wrong way round for my very different eyes, frames and earpieces bent, broken or lost, wondering where various old specs were and whether they would still work up to a point... Would I still be able to drive without the proper glasses for example? Makes your blood run cold that one. It was such a relief to awaken to a saner, more predictable world.
Tsk! I'll have to go back to panicking about the jalopy...
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>> The optician in a nearby town provided another screw and I don't think charged for
>> it (opticians can be surprisingly expensive).
>>
I've not been charged for the four or five times I've had to have that done. I'll be surprised if any opticians do charge.
Last edited by: BrianByPass on Sat 17 Dec 16 at 17:58
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>>I've not been charged for the four or five times I've had to have that done. I'll be surprised if any opticians do charge.
I've had the screws on my current specs tightened by about half a dozen local opticians and the only one to charge for this (£1) was Boots, as the said specs weren't supplied by them.
Incidentally, as it's time for me to have my eyes tested again, does anyone here have any recommendations as to the best company to use?
Thanks.
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I use a local independent optician. He's an eye surgeon at my local hospital.
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All about the same I guess. The big chains like Specsavers tend to have the more up to date equipment but I guess they all come up with the same prescription. Once you have your prescription you can of course buy your specs anywhere.
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>> Incidentally, as it's time for me to have my eyes tested again, does anyone here have any recommendations as to the best company to use?
I usually go to Boots, but I decided to go elsewhere this year after reading this:
www.theguardian.com/business/2016/apr/13/boots-staff-under-pressure-to-milk-the-nhs-says-pharmacists-union
I looked up Boots, Specsavers and Tesco on the Trustpilot review site and found that Tesco had far higher ratings than the other two and more of them as well. They were so good, I decided they must ask every customer to give them a rating, but, in the event, they didn't ask me.
Anyway, I came away from my local branch really impressed by the service I got. What I needed wasn't straightforward. I had a "lazy" eye as a child, so one lens is much more powerful than the other, plus I wanted varifocals. I was really impressed by the time they spent helping me choose the right frames and marking up the lenses so the varifocal elements were in the right place. Has lens technology moved on since 2004 when I last had a new pair of specs? In comparison with those, the new ones have much thinner lenses, so they're lighter.
My partner, who went with me, commented that their service was just as good as the independent she goes to who is well-known locally for the care he takes. Incidentally, way back, I persuaded her to go to Boots for her first pair of varifocals. They were a disaster and it took them a long time to work out that the lens technician had misread the optician's appalling handwriting.
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Thanks for that, John Boy. Unfortunately the nearest Tesco optician is some distance away.
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New specs 3/4 mths ago.
Testing went fine, chose suitable sized frames to accommodate the varifocals.
Ipad App
Sizing, positioning of the varifocal done by an App on an I-pad - quick photo & the app works out all the measurements.
Top of the range varifocal lenses were 3 x the basic varifocal -the lenses are thinner which is worth it alone.
SWMBO 2 pairs, I bought one pair (old specs only marginally different kept as spare pair)
Total £450 - so about £1.00 per week for my glasses seems OK
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Could you name the app please, FB?
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>>Could you name the app please, FB?
Nope! Specsavers ipad - not mine!
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Oh blow. I had a look in the AppStore. There are a few for inter-pupillary distance, for example. But of those that even have reviews, for every one that says it's wonderful, another says the results are hopeless and don't match what the optician says.
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>> The lenses are plastic
And so are the frames. I used to have gold-effect metal frames, but the little screws would get loose and one of the lenses would drop out (and often get chipped, in the days of glass lenses). These plastic jobs are just the thing, serious looking but not forbidding: low-key and functional. When they get fingerprinted or smeared I wipe them on my tee shirt, which they tolerate very well.
Last edited by: Armel Coussine on Sat 17 Dec 16 at 18:03
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I've never had to pay for a screw.
Just saying.
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>> I've never had to pay for a screw.
Not married then.
;>)
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I have recently moved to varifocals. There is good expanation of how it works here.
www.onlineopticiansuk.com/varifocal-progressive-lenses-explained-i128
I got it from Tesco (buy 1 pair get another free). They offered me 4 different types of varifocal lenses. I opted from the most expensive one and I can confirm I had no issue in transition (some internet reviewes stated their varifocal showing stairs at crooked lines).
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Yes, it is a good explanation. I wasn't too keen on the OTT video, but it led me to this:
www.youtube.com/watch?v=KUdPMh6nNlc
which strikes me as a good argument for having varifocal dispensing done by a (skilled) person rather than any kind of device.
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How to measure the distance between your pupils:
Put glasses on. Stand in front of a mirror. Not too close, to ensure you are looking in the distance. Take a picture.
In the printed or computer screen picture you can measure the distance between specific points on your glasses and compare with the actual same points on the actual glasses. Divide one buy the other to get the proportion.
On the photo measure the distance between your pupils and multiply it by the previously determined proportion.
Or you can ask your optician, but a bit embarrassing as they will realise you are going elsewhere to get glasses.
My optician is fantastic and twice found problems needing surgery. Unfortunately the dispensing part won’t put new lenses into existing frames if the frames are over 5 years old.
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Spectacle Optics - busbee
