Do you use the Gerstman calculated near PD for your customers with higher distance Rx's?
With every multifocal customer
Only with higher distance Rx's and multifocals
Never
Never, and what are you talking about?
During Ophthalmic Degree studies, and never again
Do you use the Gerstman calculated near PD for your customers with higher distance Rx's?
I can't even pronounce it, how am I going to use it?
wow, I forgot it even existed....used in el salvador on my mission and that was 3 years ago.
I have my own special formula (and my name is not Gerstman), but no, I measure it.
Are you some onliner scumbag trying to use this against dispensing opticians, or trying to come up with some way to get around professional dispensing?
I agree with drk (very strange) I measure each one individually.
Don't you feel better, now, Jacqui, that you've come over to the dark side?
Not trying to use this against anyone DRK, trying to better understand just how far opticians are going to give the consumer the "best possible optics" according to the formulas. Especially interested now as the industry is gearing up for getting into the DST/FF lenses and looking at the faceform, panto, and vertex distance measurements that we will probably be taking in the future.
I personally have not used this formula since my degree in Ophthalmic Science studies.
Cerebral Cortex, Vol. 9, No. 2, 137-150, March 1999
© 1999 Oxford University Press
Synchronization Between Temporal and Parietal Cortex During Multimodal Object Processing in Man
Better start reading:
http://cercor.oxfordjournals.org/cgi...l/9/2/137#SEC3
Its a long one...................
lol :DOriginally Posted by drk
Measurement only here! The Gerstman calculated, and the Ellerbrock formula only work within a limited range of power.
I use the pupilometer, and dial it in for the working distance..
Geez. I googled "Gerstman calculated pd" and get referred back to this thread.
Is this a snipe hunt?
No Doc. Gerstman is a simplfied calculation of near inset with a rule that states for every diopter of dioptric demand the optical center of each NRP should be inset .75mm. (The dioptric demand is the inverse of the reading distance in meters and is independent of the actual bifocal power).
Example: Reading distance of 40cm and an add of +1.00, the dioptric demand is 1/0.40 or 2.50. Therefore 2.50 X 3/4 = 1.9 inset per lens.
*From The "Systems" book 1988 edition.
Last edited by optical24/7; 05-21-2010 at 04:18 PM.
I thought it had to do with the output from a linear accelerator. :D
So...where does the flux capacitor fit in?
24/7, is this an additional inset correction factor to add to the near p.d., or is it simply a way to calculate near p.d. knowing only the distance p.d.? If the latter, I think it's flawed.
The latter, and you are correct. Flawed, as uncut stated, limited use.
This calculation abviuosly assumes a default value for vertex distance. What is that value?
How many other POW mavens have seen that *precise* VD values are oxymoronish?
B
Just to the left of the Contimuum Transfunctioner.
As Optical 24/7 mentioned the shortcut Gerstman described in his '73 journal article describes a method that is only suited for distant PD's that fall within a range of PD's (62 to 68) is the accepted range. This method does not correct or effects of the distant power in cases of multifocals and PAL's.
The Ellerbrock is a more accurate formula and is programmed into the cheaper asian made pupilometers.
DPD = mono distance ipd
w = working distance
c = back vertex to center of rotation
f = focal length of the lens
inset = inset
These methods are flawed over measureing for a very simple reason, we are not all built perfectly. If the patient has any sort of deficiency in their convergence then any formula falls apart. The only truly accurate measure would come from trial frame in the near power and take the PD with the patient fixating on a point at the near working distance.
Doh! Yrahg, no giving out secret formulae on the general forum. Dr.s Dhavid and Gay are now furiously scribbling a new factor on their double-secret formula.
sounds to me that they are trying to make something very simple into something needlessly elaborate, just my opinion, I could be wrong
I myself am a simple minded person and prefer to find the simple ways to accomplish my objective. All this is starting to sound like the brainaics are trying to out brainaic each other with made up terminology.
Sorta reminds me of the time I was looking for the power button to put the window up in a rental I was using. 8 year old daughter says to me, "what you looking for daddy?" as she is rolling up the window with the hand crank.
No need to over complicate the simple things in life. But if thats what you need in life to make yourself feel good, then by all means, please, enjoy.
Brainiacs, made up terminology, very insulting.
Although I didn't vote in the poll, I routinely used Gerstman's formula in my dispensing days to determine the near PD of standard multifocal lenses. In fact, the code in all of my software tools also makes use of it. Once you've used it on a regular basis for a while, you really don't need the formula, because you quickly learn to use your own rules of thumb regarding how much you should vary the inset based upon the distance prescription and addition power to nearest say, 0.5 mm.
Best regards,
Darryl
Darryl J. Meister, ABOM
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
Bookmarks