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I'm curious about both your opinion and any research anyone may be aware of into what method for measuring monocular and binocular PD respectively is best.
What are your views and what the research says on pupillometer, autorefractor, ruler, apps (and anything else you might use)
Welcome to Optiboard. I'm curious what your background in this field is.
Never used an autorefractor. App and pupilometer gave almost same results and both work off the same principle assuming the app works on reflection.Quote:
Originally Posted by Alfred001
Autorefractors are not very accurate and dont provide mono pd's.
The Gold Standard is a muscle light and a metric ruler.
Alfred,
A Pupilometer is the standard, but is unable to account for face turns and other physical anomalies.
https://healthpartnersohpe.files.wor...ns-handout.pdf
I use the client's preadjusted frame in situ with narrow vertical ink lines bisecting the corneal reflex. Adjust for differences between measurer's IPD and wearer's IPD. Use a PAL verification chart to read the results.
Best regards,
Robert Martellaro
"I use the client's preadjusted frame in situ with narrow vertical ink lines bisecting the corneal reflex. Adjust for differences between measurer's IPD and wearer's IPD. Use a PAL verification chart to read the results."
Robert- Does this explain why my wide PD'd eyes tend to ruler measure a millimeter or so larger than other colleagues as well as a pupilometer?
Can you expand on the last sentence? Verification chart???
Draw a vertical line at the corneal reflext right onto the glasses that you are planning to put lense into. Super impose the frame onto the chart with the center of the bridge aligned to the center of this chart. Read PD's off the scale.Quote:
Originally Posted by Uncle Fester
Attachment 14308
For every 1mm diference between the PD of the fitter and the subject, the fitter will over-estimateQuote:
Originally Posted by Uncle Fester
the subject's PD by 1/16 mm if the fitters PD is larger than that of the subject. -Probably Jalie.
If your binocular IPD is 74mm and the subject is 58mm, and you don't compensate, your result will be off 1mm on the high side. Not usually an issue, but when it is, the compensation is typically .5mm to 1mm, maybe a little more if the subject is a very young child.
Keep in mind that these errors are additive, if the lab is 1mm wide on each lens, and your measurement method is 1mm wide per lens, and the lens power converges the eyes 1mm more per eye at the near point than the lens design anticipates, and/or if there is prescribed horizontal prism imbalance (base out in this example), we'll be looking at errors of 2mm to 4mm or more wide per eye! Admittedly that's the worse case but you get the idea- this can go very bad really fast if we're not paying attention.
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If you're not using a pupilometer, Use this chart to determine the near PD if the work distance is less than 16"/40cm.
If stop distance equals 27mm, the near multiplier for a work distance of
40cm is .937
35cm is .928
30cm is .925
25cm is .903
20cm is .881
That's it. Position accurately and eliminate errors due to parallax.Quote:
Originally Posted by Oscar
Hope this helps,
Robert Martellaro
Quote:
Originally Posted by Robert Martellaro
Is it possible to avoid making these calculations by just having the dispenser shift their position so that the eye's line up with the patient? dispenser uses left eye and lines up with patient's right eye and measures "0". Dispenser uses right eye and shifts their body to line up with patient's left eye and measures binocular. Repeat step 1 to correct alignment of PD ruler. Check bridge for monocular measurement.
That may introduce errors, I think. If you move more for one eye than the fellow eye we might change the binocular PD, which is arguably more important then the monocular PD. A simple rule of thumb would probably suffice- modify by .5mm for differentials of 6mm to 10mm, and 1mm for larger differences. Or use a pupilometer, which eliminates parallax errors (but not errors due to face/head turns).Quote:
Originally Posted by Oscar
Note to pupilometer users- clean with 70% isopropyl alcohol after every use, especially during flu season. Calibrate routinely, especially after hard use.
Best regards,
Robert Martellaro