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I don't think PD is part of your optometrist's prescription; it wasn't on the prescription they gave me when I walked out the door. I can't remember who measure

I don't think PD is part of your optometrist's prescription; it wasn't on the prescription they gave me when I walked out the door. I can't remember who measured it but I copied it down from my optician's order when I ordered some glasses. They're both in the same office (which is pretty common) at Berkeley School of Optometry. My PD is L 32.5 R 31.5. The ruler technique is neither this accurate nor does it distinguish left from right. Yeah, I'm a little lopsided. I keep this information now in a Google Doc along with my eye size, bridge size, temple length and current frames. Since I'm a nerd, I read up on lens materials and now I use Trivex single vision aspherics for readers and drivers. I'm a lot more knowledgable now about my available choices. These are some of the Trivex single vision choices: http://www.eyeglasslensdirect.com/Trivex-Single-Vision-Lenses-s/147.htm http://www.eyeglasslensdirect.com/Trivex-Single-Vision-Lense... If you have major astigmatism problems you really must educate yourself on the choices. There are free form lenses with much more complicated computer driven prescriptions+lenses customized to the individual. Also, you can get free form lenses tailored to computer use. http://seikoeyewear.com/lenses/progressive-lenses/seiko-individual-lenses/ http://seikoeyewear.com/lenses/progressive-lenses/seiko-indi... http://seikoeyewear.com/news/seiko-pcwide http://seikoeyewear.com/news/seiko-pcwide Another thing is that if you ask your optometrist for a prescription for readers, they'll usually set the focal distance to something like a foot. Well, I'm typing on my laptop and it's about 3 feet away. This is intermediate or tool distance and a prescription for that is a massive quality of life improvement. If you spend some time on an online site like www.framesdirect.com, you can educate yourself quite a bit on the available choices. When you walk into an optician's office, they really only have a certain amount of time to work with you since they have to make a nickel; so you usually spend a lot of time on frames. I haven't even ordered online yet but educating yourself before you walk into a brick and mortar optician's office will make you a little annoying but then you'll get a better result.

drdeadringer 9y ago
> I don't think PD is part of your optometrist's prescription; it wasn't on the prescription they gave me when I walked out the door. I can't remember who measured it but I copied it down from my optician's order when I ordered some glasses. It wasn't on mine either, but on advice given to me I called up the optometrist to ask and they gave it to me with no problem at all. I've started keeping//tracking my prescription some time ago just for good measure.
- dminor 9y ago
  My optometrist refused to give it to me unless I bought glasses from them. They claimed the number depends on the specific glasses you have. Fortunately I was able to find it on a prescription from a previous provider.
  - drdeadringer 9y ago
    I'm glad you were able to get the information from a more reasonable provider. I guess I was lucky to some extent, and I hope we're all able to find "better" providers.
  - boptom 9y ago
    Your pupillary distance won't change depending on the frames you buy (it is a body measurement after all). However, where the optical centre of a lens is placed within a frame can vary from the PD a fair bit, depending on how the frames sit on your face, as the contact point of the frames do not always line up perfectly with the top of the nose bridge. Also, an oft looked over measurement is the distance from the bottom of the frame to the centre of the lens, which is important with complex prescriptions and cannot be measured without looking at the frame on your face. Having said this, with most low prescriptions the human tolerance is so high that it does not matter.
copperx 9y ago
Isn't Trivex optically worse and more expensive than the standard CR-39 and just insignificantly less thick? I have a -4.00 prescription, and I didn't think Trivex was worth it, because I don't need shatter protection. Also, interestingly, in Mexico PD is part of the prescription.
- CalChris 9y ago
  Not optically worse. CR39 has lower index of refraction (1.498 vs 1.54) and so it is heavier. It has worse chromatic aberration (Abbe 58 vs Trivex 45). So it's really only good for light prescriptions. Trivex is also easily drillable making rimless easy, rimless->lighter; PC tends to crack easily. But yes Trivex is a little more expensive than CR39 but in my experience a lot better. If your lenses last 2 years, lenses are not where you should save money. http://www.mastereyeassociates.com/eyeglass-lens-materials http://www.mastereyeassociates.com/eyeglass-lens-materials
  - mrob 9y ago
    CR39 has better chromatic aberration. Higher Abbe number means less aberration. CR39 has the lowest chromatic aberration of any material commonly used to make glasses.
    - CalChris 9y ago
      Yeah, I got that backwards. Point is that CR39 is not exactly better optically. Trivex is significantly better chromatically than PC, 1.60, ... In addition, Trivex acts as a UV cutoff filter. What I couldn't figure out is whether a CR39 lens' comparative thickness (prism length) vs a thinner Trivex lens degrades its chromatic aberration advantage in practice. http://eclecticeyewearaustin.com/wp-content/uploads/2016/05/Lens-thickness.jpg http://eclecticeyewearaustin.com/wp-content/uploads/2016/05/...
      - boptom 9y ago
        Generally, you would expect lenses with a higher refractive index to be thinner. However, due to the selling point of Trivex being "shatter proof" it has a greater centre thickness (to pass safety lens regulations), and thus the edge thickness is also comparable to CR-39.
chris_st 9y ago
> Well, I'm typing on my laptop and it's about 3 feet away. My eye doctor (don't remember which one he is, sorry) recommended bifocals that are computer-range above, reading below. Simply fantastic. Couldn't recommend it more.
- CalChris 9y ago
  Well, I'm nearsighted. So I can type on my phone without glasses at all. So I was really kinda annoyed when they set the focal distance on some progressives I had to 1 foot. Laptop reading was possible but uncomfortable. I have given up on progressives altogether. Single vision for me is awesome. But my big recommendation is to educate yourself on the choices available cuz you can't expect an optometrist/optician to do this in five minutes.
  - chris_st 9y ago
    Whichever way you go, you're absolutely right to get what is correct for you, which (usually) requires digging on your own. Luckily for me, as I say, my eye doc recommended that layout.

drdeadringer 9y ago

> I don't think PD is part of your optometrist's prescription; it wasn't on the prescription they gave me when I walked out the door. I can't remember who measured it but I copied it down from my optician's order when I ordered some glasses. It wasn't on mine either, but on advice given to me I called up the optometrist to ask and they gave it to me with no problem at all. I've started keeping//tracking my prescription some time ago just for good measure.

dminor 9y ago
My optometrist refused to give it to me unless I bought glasses from them. They claimed the number depends on the specific glasses you have. Fortunately I was able to find it on a prescription from a previous provider.
- drdeadringer 9y ago
  I'm glad you were able to get the information from a more reasonable provider. I guess I was lucky to some extent, and I hope we're all able to find "better" providers.
- boptom 9y ago
  Your pupillary distance won't change depending on the frames you buy (it is a body measurement after all). However, where the optical centre of a lens is placed within a frame can vary from the PD a fair bit, depending on how the frames sit on your face, as the contact point of the frames do not always line up perfectly with the top of the nose bridge. Also, an oft looked over measurement is the distance from the bottom of the frame to the centre of the lens, which is important with complex prescriptions and cannot be measured without looking at the frame on your face. Having said this, with most low prescriptions the human tolerance is so high that it does not matter.

copperx 9y ago

Isn't Trivex optically worse and more expensive than the standard CR-39 and just insignificantly less thick? I have a -4.00 prescription, and I didn't think Trivex was worth it, because I don't need shatter protection. Also, interestingly, in Mexico PD is part of the prescription.

CalChris 9y ago
Not optically worse. CR39 has lower index of refraction (1.498 vs 1.54) and so it is heavier. It has worse chromatic aberration (Abbe 58 vs Trivex 45). So it's really only good for light prescriptions. Trivex is also easily drillable making rimless easy, rimless->lighter; PC tends to crack easily. But yes Trivex is a little more expensive than CR39 but in my experience a lot better. If your lenses last 2 years, lenses are not where you should save money. http://www.mastereyeassociates.com/eyeglass-lens-materials http://www.mastereyeassociates.com/eyeglass-lens-materials
- mrob 9y ago
  CR39 has better chromatic aberration. Higher Abbe number means less aberration. CR39 has the lowest chromatic aberration of any material commonly used to make glasses.
  - CalChris 9y ago
    Yeah, I got that backwards. Point is that CR39 is not exactly better optically. Trivex is significantly better chromatically than PC, 1.60, ... In addition, Trivex acts as a UV cutoff filter. What I couldn't figure out is whether a CR39 lens' comparative thickness (prism length) vs a thinner Trivex lens degrades its chromatic aberration advantage in practice. http://eclecticeyewearaustin.com/wp-content/uploads/2016/05/Lens-thickness.jpg http://eclecticeyewearaustin.com/wp-content/uploads/2016/05/...
    - boptom 9y ago
      Generally, you would expect lenses with a higher refractive index to be thinner. However, due to the selling point of Trivex being "shatter proof" it has a greater centre thickness (to pass safety lens regulations), and thus the edge thickness is also comparable to CR-39.

chris_st 9y ago

> Well, I'm typing on my laptop and it's about 3 feet away. My eye doctor (don't remember which one he is, sorry) recommended bifocals that are computer-range above, reading below. Simply fantastic. Couldn't recommend it more.

CalChris 9y ago
Well, I'm nearsighted. So I can type on my phone without glasses at all. So I was really kinda annoyed when they set the focal distance on some progressives I had to 1 foot. Laptop reading was possible but uncomfortable. I have given up on progressives altogether. Single vision for me is awesome. But my big recommendation is to educate yourself on the choices available cuz you can't expect an optometrist/optician to do this in five minutes.
- chris_st 9y ago
  Whichever way you go, you're absolutely right to get what is correct for you, which (usually) requires digging on your own. Luckily for me, as I say, my eye doc recommended that layout.