measuring lens power on progressives

[Daniel Cunningham]

Hi:

One of my students asked me this. If the fitting cross is supposed to be at pupil centre, why do we measure the distance power in the circle above the fitting cross?

Daniel

[Refractingoptician.com]

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[DragonLensmanWV]

Hi:

One of my students asked me this. If the fitting cross is supposed to be at pupil centre, why do we measure the distance power in the circle above the fitting cross?

Daniel

We have far better luck fitting it 2 mm lower than center of pupil.

[Refractingoptician.com]

;;

[Fezz]

This link was written by our very own Darryl Meister. It has just about everything you ever wanted to know about progressives.


http://www.opticampus.com/cecourse.p...essive_lenses/

[Win C]

The circle above is the only reference point from which the Doctor's Rx can be verified ,,, because any other point on the lens will yield a different RX .

If that is the case, the power measured at the fitting cross will not be prescribed power for the distance? That would also mean that if we fit the fitting cross to patient's pupil centre, the patient will not see clearly thru the fitting cross. :hammer:

[HarryChiling]

I know old post, but no answer. Because the pupil or in this case the lensometers stops apperature size is large enough where we need to ensure that the entire apperature is outside of the zone of progression.

[ayoco]

the aperature of your lensometer is 9mm. if you check power at the cross, half the aperature is in the intermediate zone. checking 4 mm above the cross moves the zone far enough away as not to blur the image.