Exact reading power

**fistkuen** · 01-08-2011, 06:07 AM

hi, everyone, how do i know exactly the reading power of PAL with a lensmeter because different lens designs lead to different additional power shown? THX

**chip anderson** · 01-08-2011, 09:17 AM

Measure it down and in below the "minimum seg ht." from the puplillary center. And then there is the add power imprinted temporally on the lens.

**For-Life** · 01-08-2011, 09:23 AM

Dot them up, based on the markings, and find where the reading circles are. Read in there

**uncut** · 01-08-2011, 09:49 PM

And.....if you are finding the power within the check circle is not what you think it should be, or doesn't match the inscribed value.............contact the manufacturer for an excuse!

**MarySue** · 01-09-2011, 01:08 PM

Originally Posted by fistkuen

hi, everyone, how do i know exactly the reading power of PAL with a lensmeter because different lens designs lead to different additional power shown? THX

If you're using a digital model, you must calibrate daily, and use the right abbe value preset. If not, you won't be able to accurately vert digital lenses on a barrel focimeter (lensmeter). The reasons why are an hour long session on optics and focimeter use, which Darryl Meister might be able to condense to post size, but I'm no Darryl Meister!

Cheers! Mary Sue

**chip anderson** · 01-09-2011, 02:41 PM

The exact reading power doesn't really have the importance you might think. You don't know what point the patient will be looking through at an exact moment. With most progressives the power varies all over the lens. Some a lot more than others to be sure but it varies non the less. If the patient is attempting to read at 18" he may look a little above the sweet spot reading power. This if he looks at a slight angle all sorts of cylindric aberrations come into play. As long as they are both the same at a given height and inset, the difference between +1.87; +2.00; and +2.12 is rather accademic for anyone other than you, the inspector of the lenses. This all assumes that the patient can read at the distance he wants to of course.

Chip

**musicvirtuoso** · 01-22-2011, 11:54 AM

Originally Posted by MarySue

If you're using a digital model, you must calibrate daily, and use the right abbe value preset. If not, you won't be able to accurately vert digital lenses on a barrel focimeter (lensmeter). The reasons why are an hour long session on optics and focimeter use, which Darryl Meister might be able to condense to post size, but I'm no Darryl Meister!

Cheers! Mary Sue

I'm not an expert in lensometry and I'm no Darryl Meister either, but let me take a crack at it: If the autolensometer is set to an incorrect abbe value, any compensation for lateral or longitudinal chromatic aberration would be incorrect as lenses of different abbe values would produce varying degrees of dispersion. (I have to be honest - I didn't think that autolensometers did this, and doubt that its effects in most lenses would truly create large enough errors to cause off-power readings) Hope I didn't just make a fool of myself - but you live and learn...

**MarySue** · 01-23-2011, 12:32 PM

Originally Posted by chip anderson

the difference between +1.87; +2.00; and +2.12 is rather accademic for anyone other than you, the inspector of the lenses. This all assumes that the patient can read at the distance he wants to of course.

Chip

Chip - the difference between +2.00 and +2.12 is "me reading or me not reading? ...It isn't academic, its subjective and unique to the individual. The prescriber is the one who determines, with the patient what RX is required, not the d.o. checking the lens!

This opens another can of worms - have you or has anyone here read the new international standard for lens tolerances? It's mind-blowing.

**chip anderson** · 01-23-2011, 12:39 PM

One beautiful thing about EU, international Standards and any other standard outside the US. They have no authority over us.
As long as I stay in the US I really don't care what "international standards", the EU or the United Nations says. I didn't vote for them, gave them no ruling authority and have little use for them.
Reguardless of certian political attitudes afoot, it isn't one world yet.
If I put a seg. 1mm lower than some French company says and the patient can read well, who cares?
Are you going to tried at the Hague?

Chip

**MarySue** · 01-23-2011, 01:13 PM

Originally Posted by chip anderson

One beautiful thing about EU, international Standards and any other standard outside the US. They have no authority over us.
As long as I stay in the US I really don't care what "international standards", the EU or the United Nations says. I didn't vote for them, gave them no ruling authority and have little use for them.
Reguardless of certian political attitudes afoot, it isn't one world yet.
If I put a seg. 1mm lower than some French company says and the patient can read well, who cares?
Are you going to tried at the Hague?

Chip

I live in New Zealand Chip - USA born and bred, and living abroad, as a permanent resident here ... And, New Zealand isn't part of the EU. In fact Europe is approximately 11390 miles (18331 km) away from New Zealand. An international standard affects the USA - because it affects products you export, and import.

As for being tried at the Hague - I suppose as the de-facto judicial capital of the UN, I could be tried there - but I wouldn't be able to guess what crime I could commit to see such a consequence ... maybe answering this post?

**chip anderson** · 01-23-2011, 01:44 PM

My point is that it is almost true that we as retail opticians are not exporting anything.
Perhaps what we buy may have to conform to someone's rules but what me make and sell must only conform to our state, province, city, or country's rules.
If it's not legal in Denmark, who cares?

Chip

**MarySue** · 01-23-2011, 05:59 PM

Originally Posted by chip anderson

My point is that it is almost true that we as retail opticians are not exporting anything.
Perhaps what we buy may have to conform to someone's rules but what me make and sell must only conform to our state, province, city, or country's rules.
If it's not legal in Denmark, who cares?

Chip

Too funny - classic

**conantoptics** · 01-24-2011, 02:18 AM

Mary Sue, Hello!

I am reading the standards, AS 2228.1-1992, AS NZS 1337, there are some diference from ANSI Z80.
But it doesnt matter, since our LAB QC standard is higher; only in this way, we can sell to oversea clients.

Sue, you are right, by saying the exact power and Abbe set, :)

after the setting, you can check it, using the method For-life suggesed:

Dot them up, based on the markings, and find where the reading circles are. Read in there

**MarySue** · 01-24-2011, 02:07 PM

Originally Posted by conantoptics

Mary Sue, Hello!

I am reading the standards, AS 2228.1-1992, AS NZS 1337, there are some diference from ANSI Z80.
But it doesnt matter, since our LAB QC standard is higher; only in this way, we can sell to oversea clients.

Sue, you are right, by saying the exact power and Abbe set, :)

after the setting, you can check it, using the method For-life suggesed:

Dot them up, based on the markings, and find where the reading circles are. Read in there

Thanks Kevin!