Sure. My PD is 61.5mm. That means that the middles of my lenses
should be 61.5mm apart.
That means that half of each lens should be between my pupils. So, 2
* (1/2 lens width) = PD.
But, uh oh, we have a bridge in there, too. So, we have to include it, too.
2 * (1/2 lens width) + bridge = PD
Now, simplify the equation... 2 * 1/2 = 1.
lens width + bridge = PD.
So, using my PD, and a 17mm bridge width, we come up with a
theoretical "ideal" lens width of:
LW + 17 = 61.5
LW = 61.5 - 17
LW = 44.5mm
My (theoretical) ideal lens width, for a pair of glasses with a 17mm
bridge, would be 44.5mm. This would result in my pupils being
perfectly centered in the lenses.
-- Chuck Knight
On Mon, Aug 24, 2009 at 8:02 PM, Susan<[email protected]> wrote:
>
> Chalo:
>
> Can you explain this a bit more? I am not understanding what you mean.
>
> "One nice rule of thumb your optician might not tell you is that if
> you match
> the lens width plus the center width to your PD, then your eyes will
> fall in the centers of the lenses."
>
> Thanks!
> Susan
>
> On Aug 24, 12:59 pm, Chalo <[email protected]> wrote:
>> hippiedyke13 wrote:
>>
>> > At first I was extremely skeptical about buying
>> > glasses online, but after reading the rave reviews I am willing to
>> > give it a try. Especially after I went to Costco, spent an hour
>> > looking at frames, picked out a pair, but was told that I had to bring
>> > a copy of the prescription in. I had only gotten glasses a year ago,
>> > and this was the first year my prescription hasn't changed. They had
>> > my prescription on file from a year ago but they said it had expired.
>>
>> One year is not very long. For most people, measurements taken only
>> one year ago are likely to be correct. Even if not, it's better to
>> wear new fresh lenses than old scratched ones with the same
>> prescription. Most new glasses being as costly as they are, many
>> folks wait too long before buying replacements.
>>
>> When I was your age, I usually kept my glasses about two to three
>> years between replacements-- but this was more a result of damaging
>> them than noticing problems with the 'script. Before I discovered
>> Zenni Optical, I was using an assortment of glasses between three and
>> about fifteen years old, all with slightly different prescriptions.
>> For what it's worth, the newer glasses did not necessarily give me
>> better vision.
>>
>> Keep in mind that you are still young enough for your eyes to change
>> significantly over relatively small spans of time. Don't go so long
>> between new prescriptions that you can tell you are not getting your
>> best available vision. This is all pretty inexact stuff, but you can
>> probably tell when your glasses aren't quite right.
>>
>> With any luck, you have kept some old pairs of glasses so you can
>> measure them for a basis of comparison. Educated guesses based on
>> past experience can get you glasses that look just as good or better
>> than what you've had before, even without trying them on. One nice
>> rule of thumb your optician might not tell you is that if you match
>> the lens width plus the center width to your PD, then your eyes will
>> fall in the centers of the lenses. Frames narrower than this can look
>> pretty dumb.
>>
>> I say start with a couple of cheap frames and get used to doing your
>> own fitting and adjustment. I can tell you from my own experience,
>> it's easier to heat and bend a $17 pair of glasses than a $400 pair.
>> Wire frames are easier to reshape, but plastic ones are more likely to
>> occupy the bottom of the price range. I'd stay away from memory
>> titanium alloy glasses for your first try, because the memory metal
>> parts of the frame can't be reshaped easily or precisely. (Pure
>> titanium can be bent as necessary.)
>>
>> > I'm really itching to buy some glasses but I still have to get my PD..
>> > On Monday I will call my ophthalmologist and ask for it.
>>
>> You can measure your own PD, especially if you have a competent friend
>> help you out. This Wikipedia article has some pointers and links:
>>
>> http://en.wikipedia.org/wiki/Pupillary_distance#Measuring_pupillary_d...
>>
>> Chalo
>
> >
>
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