Specsavers - extra light lens - difference in weight?

parapusher

I have paid for extra light lens for my son. He has a high prescription and I was told that normal lens would be too heavy. We went to specsavers who give a free pair. To save money buying extra thin on both pairs, they agreed to make the extra pair as normal lens, so he could just use them as a spare pair in an emergency if the others were broken. We had to collect them at different times, as they both weren't ready together. We got the second (heavy) pair tinted before collection, as he is having problems with sensitivity to the sun. I have just had both pairs to clean for him and though they weighed much the same. I put them on the scales and found the 'extra light' lens glasses weighs 8 grams less than the 'heavy' ones! I have been charged £110 for a saving of 8 grams :mad: The total bill was £215! My question is, does anyone else have two pairs of glasses, light and 'heavy' and do you know the difference in actual weight? The frames are identical in our case. I had to pay as he is autistic with learning difficulties and 19 yrs old. I hope to recoup some as he is still on my tax credit until Monday when he's 20, so should qualify for the voucher but that's not much.

Thanks for any help
Lynne

Carmen_Queasy

Is it possible they could be different materials? My own thinned down everyday pair are glass while my spare normal ones are plastic so the plastic is lighter than the glass but the glass looks thinner.
I buy extra light frames mostly out of vanity rather than comfort- they don't feel much different to me, they just look better.

jd87

If it's any consolation I have a little physics lesson which might make you realise it was worth spending the extra money:

Every object has a "centre of gravity" which is basically the point where the weight of the object is spread evenly around it. For a pair of glasses you want the centre of gravity to be as far back as possible towards your ears; this is so that the glasses won't try to slide down your nose.

If you have heavy lenses, more of the weight of the glasses will be towards the front and the glasses will try to slide down your nose. A pair of glasses with lighter lenses has a centre of gravity further back.

All of this might sound obvious - but the important thing you might not have thought about is this: 8 grams might not sound like a big difference, but it is 8 grams at the very front of the glasses, so it is 8 grams that have a big effect on the centre of gravity. Even though the total weight of the glasses hasn't changed much, the weight distribution is much better.

Anyone reading this who still isn't convinced should remember what their physics teacher tried to teach them about "moments".

Hope this helps.

parapusher

Thanks for the explanation. I wasn't allowed to do physics at school, because I was a girl !

Lynne

ali-t

I can't give a scientific explanation but I always found that it depended on the shape and size of the frames how heavy the glasses are. For example if there are rounded edges compared with squarer ones there might be a difference. Unless your son has 2 identical pairs of specs it might be hard to put the weight difference into context.

Tigsteroonie

Were the lenses described as "extra light" in terms of weight, or did they mean "extra thin"?

I have a high prescription, and get my main pair of specs super-thinned for everyday wearing; the second free pair I have as normal thickness and tinted, to use as sunglasses.

But, to be honest, I don't notice a difference in weight when I switch between the two.

parapusher

They said the lenses were 'extra light' and that the normal ones would be too 'heavy'. So naturally I thought they were talking about weight. My son isn't concerned with his appearance, he is autistic, so doesn't worry what his glasses look like providing he can see where he is going, and the computer keys! Yes, the frames are identical, they were the only sturdy looking ones available - he breaks them on a regular basis. I have upped my insurance to include personal belongings now!
I think we will change opticians next year.