Glasses prescription - help with understanding it

travel_freak

Hi

I just wondered whether there are any opticians on here who could help me understand something written on my prescription.

I'm hoping to order some glasses online but my prescription reads "Any other relevant information: 1.67 lens minimum".

I haven't had this written on prior prescriptions so am wondering what its significance is and if this restricts my choice of glasses online.

I am -4.75 in one eye and minus 3.75 in the other.

Also I have had two eye tests recently one at Dollond & Aitchison and the other at Tesco as I was having my contact lens assessment done there. They are within about a month of each other but each gives different readings for distance and for the "Cyl" and "Axis" measurements so am not sure which one to go with!!

Many thx if anyone can help with the above.

tidus

The optician has recommeded that you have thinner lenses, thats all - 1.67 refers to the refactive index of the lenses - the higher the value the thinner your lenses will be. It doesn't stop you getting glasses in any material, its just a recommendation, not part of your prescription.

Can't really help you with which prescription to go with - the latest one I guess If you post them I can tell you how much difference there is - there are 2 ways of writing a prescription as well which will make them look very different, although they can be virtually identical, so this might be the problem.

travel_freak

Hello Tidus,

Many thanks for your helpful reply.

As requested, the two prescriptions are as follows - they seem really different to me(!):

D&A prescription (with Tesco's prescription in brackets):

Sph
Right -4.50 (-4.75)
Left - 3.50 (-3.75)

Cyl
Right -0.50 (-0.50)
Left - 0.50 (-0.25)

Axis
Right 155 (165)
Left 10 (5)

I think I'm inclined to go with the D&A "Sph" measurements as the Tesco ones seem high to me. Up until these most recent tests I was wearing contact lenses which were below the D&A strengths and I seemed to be able to see fine with these.

I don't understand the Cyl and Axis measurement differential though - will these affect the glasses I have made or are they more for contact lens purposes?

Also looking back at previous year's prescriptions the Cyl and Axis measurements have always varied - is it normal for these to fluctuate as I had thought this was something to do with the shape of the eye and so should be a fixed measurement - excuse dimness here...!

Thanks again.

Running_Horse

Did you mean to say:

Right -4.50/-0.50 x 155
Left -3.50/-0.50 x 10

and

Right -4.75/-0.50 x 165
Left -3.75/-0.25 x 5

Not only would 1.67 be a good idea, you have the kind of prescription that would see the biggest cosmetic benefit.

The prescriptions are not hugely different. You should see a qualified optician who will explain them to you.

I am not an optician, but did used to make glasses.

tidus

The only real difference is the Tesco prescription is slightly stronger on the Sphere (the myopia correction). The slight differences on Cylinder and Axis (which describe the astigmatism correction) are pretty much insignificant. One of these prescriptions is probably slightly more "accurate" than the other, but I can't tell you which. The average person could have both made up and would probably struggle to tell the difference, so I wouldn't worry too much.

The Cyl and Axis will be built into your glasses, but are too low to incorporate into contact lenses. The lowest Cyl power available in contacts is -0.75 unless specially made. The level of astigmatism depends partly on eye shape but also the shape of the cornea, which changes throughout life in many people. Usually there is a slow increase in the Cyl power, but not always - no hard and fast rules.

A note about contact lens powers - the power of your CLs will be lower than your spectacle prescription due to them being closer to your eyes. This is why you have to have seperate spec and CL tests. If a Cl was -4.00, for example, the specs prescription is likely to be -4.25 or -4.50. There is a bigger difference with higher presriptions. Don't try to judge your spec presription based on your CLs - it should be slightly higher.

geri1965_2

tidus wrote: »

A note about contact lens powers - the power of your CLs will be lower than your spectacle prescription due to them being closer to your eyes. This is why you have to have seperate spec and CL tests. If a Cl was -4.00, for example, the specs prescription is likely to be -4.25 or -4.50. There is a bigger difference with higher presriptions. Don't try to judge your spec presription based on your CLs - it should be slightly higher.

That's right, I am -10.25 for my glasses, and only -9 or -9.5 for lenses.

travel_freak

Thank you so much Tidus for your comprehensive reply and taking the time to explain everything - I am very grateful to you for putting my mind at rest as it just seemed to me as if the two prescriptions were very different to each other.

I'm going to try ordering quite a cheap online pair of glasses for one of the specs and see how I get on with them and go from there.

Once again, thanks for your help.

Running_Horse

How are you going to get your PD for your online glasses?

On your prescription it will make a lot of difference. A lot.