Varifocal specs and online suppliers?

[griffljg]

Re: Varifocal specs and online suppliers?

How do these online suppliers know how to adjust the lenses for astigmatisms?

Cheers

Larry

[Ian]

Re: Varifocal specs and online suppliers?

How do these online suppliers know how to adjust the lenses for astigmatisms?

Cheers

Larry

I'm not sure how it works in Australia, but here in the UK you are legally entitled to the prescription data after your eye test so you can use it to buy prescription glasses from suppliers other than the opticians where you had the eye test. The prescription has all the necessary information for the supplier of your choice to ensure the glasses are correct for your needs, including astigmatism (which I have in both eyes).

Ian

[Patrick]

Re: Varifocal specs and online suppliers?

[Ian]

Re: Varifocal specs and online suppliers?

Hi Patrick - the quote I had was for practically the top of five different lens types plus frames and anti-reflective coatings, etc. They way they sold it, you really had to go for the best quality varifocal lens type for the best view through them.

Ian

[Ian]

[Autumn]

[Ian]

Re: Varifocal specs and online suppliers?

Thanks Audrey; the glasses are sent from a UK base so there is no duty. The site has a lot of customer reviews and there is no mention of import duty.

Ian

[Ian]

Re: Varifocal specs and online suppliers?

My distance glasses arrived today - 6 days after the first pair ordered at the same time. The frame is better quality (half rim) than the very cheap intermediate glasses that arrived last week and according to the supplier there are titanium components in its construction although I went for a black finish so it's not obvious. The glasses are very light - just 15 grams with lenses compared to the similar style glasses that are being replaced (19g) and that's despite the new pair having a larger lens area.

I did specify more expensive polycarbonate lenses because I wanted 100% UV protection and more resistance to chipping which has previously been a problem with cheaper plastic lenses I have had. Polycarbonate lenses also have a slightly higher refractive index so the lenses should be a little thinner and lighter (not that obvious to be honest). But I have noticed one negative aspect compared to my older glasses and that's some noticeable fringing when looking at acute sideways angles without turning my head. I have seen some comments online regarding this issue with polycarbonate lenses. It's not a big issue but may dictate my future choice of lens materials away from polycarbonate.

Once again the excellence of my new prescription has been confirmed as general vision with the new specs is markedly improved over my old pair.

So I managed to get two pairs of glasses, both with anti-reflection coated lenses, with good quality if not designer frames for under £65, including shipping. I'm definitely pleased as the coating option alone would have amounted to £60 for two pairs of glasses from my high street national chain opticians.

Ian

[Ian]

Re: Varifocal specs and online suppliers?

Oh dear, the polycarbonate lenses I specified for my distance vision glasses were definitely a mistake. Off axis viewing is noticeably degraded and chromatic aberration is very noticeable. I've not come across problems like this before. I'm going to have to see if I can get the lenses changed. The FAQ on the website does say that viewing quality is not a feature of polycarbonate lenses but I didn't see that until today! They say it takes a couple of weeks to adapt but the more I wear these glasses the more frustrated I'm getting. The irony is that the cheaper intermediate vision specs I ordered are perfect in this regard.

Ian

[Ian]

Re: Varifocal specs and online suppliers?

Update: Remarkably Selectspecs responded to my email within minutes and reminded me (I actually wasn't aware) that there is kind of satisfaction guarantee so they will replace my glasses as I got back them within 7 days. There is a modest handling charge and if I need more expensive lenses I may have to pay the difference but that seems entirely reasonable to me. Now very happy again!

Ian

[Bob Ross]

Re: Varifocal specs and online suppliers?

Oh dear, the polycarbonate lenses I specified for my distance vision glasses were definitely a mistake. Off axis viewing is noticeably degraded and chromatic aberration is very noticeable. I've not come across problems like this before. I'm going to have to see if I can get the lenses changed. The FAQ on the website does say that viewing quality is not a feature of polycarbonate lenses but I didn't see that until today! They say it takes a couple of weeks to adapt but the more I wear these glasses the more frustrated I'm getting. The irony is that the cheaper intermediate vision specs I ordered are perfect in this regard.

Ian

Hi Ian,
As far as I know both pair of my glasses are polycarbonate and I have never seen any noticeable aberrations. My lenses are large for reading/scanning and smaller for the varifocals/progressives.
One thought here is that "Polcycarbonate" is a family name(in the land of organic chemistry) for a variety of formulae, so one person's polycarbonate might not be another's.
Bob

[Ian]

Re: Varifocal specs and online suppliers?

I have been doing some more research. My cheaper glasses use CR39 plastic, which most glasses lenses are made from these days. It has a reasonable refractive index so lenses aren't too thick and the optical 'Abbe' value is almost as high as optical glass (which is where polycarbonate falls down as it has a very low Abbe value). Abbe is measure of the optical dispersion in the optical material. A higher Abbe value means more light is focused correctly, vision is brighter, with more contrast and free of chromatic aberrations. CR39 has an Abbe value of 59, Crown optical glass is 60 and polycarbonate is just 30. A popular relatively new material for glasses lenses is Trivex and this has an Abbe value of around 47 which is inbetween polycarbonate and CR39 but has better impact resistance than CR39 and is similar to polycarbonate but offering better optical quality than polycarbonate. Sales literature suggest that Trivex optical quality is practically as good as CR39 but with its lower Abbe rating I'd be suspicious of that. It's also slightly better in refractive index so Trivex lenses are slightly thinner than CR39.

To be honest the optical quality of polycarbonate, especially to photographers I would guess who are more sensitive to optical imperfections, is shocking. People should be warned about polycarbonate lenses! However, they have their place where impact and shatter resistance is important, like in sports activities.

Ian

[Horacio]

Re: Varifocal specs and online suppliers?

Hi Ian, I have been using varifocal polycarbonate lenses since more than 20 years and have changed many pair of glasses, without any trouble in my vision or handling the cameras. I guess and wish so that you have to go through the curve of brain compensation for all this minor issues. H Whenever I had a problem, it always was related to minor or subtle inadequacies ot the prescription. Horacio

[Bob Ross]

Re: Varifocal specs and online suppliers?

Good info, Ian. What may be happening to Horatio and me is that shops dispensing glasses don't want to see you come back so they do the research and just tell you it is the best or the newest polycarb stuff available.
You could have some fun and have a local "shoppe" take a look at the pair in question to see if they can see a problem under their scope. My opthomologist does this and has also been asking about where we got them.
Bob

[Ian]

Re: Varifocal specs and online suppliers?

I was very pleased that SelectSpects changed the lenses in my glasses for the standard CR39 types without charge, which is part of their warranty as long as you let them know of problems within 7 days. If I had requested more expensive lenses I would have had to pay but in this case the CR39 lenses are cheaper than the polycarbonates that I wasn't happy with. There was a return postage charge of £8.50 and of course I had to pay for postage to return my glasses in the first place.

My re-glazed frames arrived back after about 10 days and they are much-improved. There is still a little CA in the extreme edges of the view but these lenses are wider than my old glasses. There is more contrast and clarity than the polycarbonates too. The rejected polycarbonate lenses were supplied in a small envelope along with my glasses.

But after several weeks with single vision lens glasses in my new prescription the need to swap glasses so frequently has been quite aggravating so I have gone and ordered some varifocals after all. Once again I used Selectspecs but I decided that ordering purely online was out of the question. Fortunately, they have one walk-in high street location in the UK down at Westgate on Sea so I ventured down there yesterday and was properly measured up (fitting only as I already had an up to date prescription - they found that my pupiliary distane that I measured myself was out by 3mm) and spent a good deal of time selecting frames that would work best with the varifocal lens requirements. I've gone for a very smart (designer-look lightweight half-rimless) frame and Selectspecs' top spec. freeform varifocal lens but stuck with the CR39 1.50 index plastic lens material as this will have the best performance for low dispersion and so the least off-axis chromatic aberration. My prescription means lens thickness is not a major concern so no need for higher index lenses. The whole lot including anti-reflection coatings, UV protection coating and scratch-resistance coating and including postage to my home address, just under £90. This would have cost at least £300 at my local opticians. Probably take a couple of weeks to be made up and sent to me - will let you know how they turn out.

Ian