How to choose the right progressive lenght corridor

[george dimitrov]

Dear All,

The modern free form PAL's offer wide variety of progression corridor lenghts - 10, 11, 12, 13, 14, 15, 16mm., and so on.
In the past the rule was to fallow the frame shape deep as a guide - top the deep frames - long coridor and short to short frames, having in mind that, the long coridor offer wide near vision, and short offer narrow.
At present I suppose this is not the right way, because the proper corridor has to correspond to the patient pupils hight at reading position.
I began to observe the client's pupil positions durring the reading, and note that, almost everybody lowers his eyes at maximim 12mm down?!, so he will not be so happy to adapt to progression lengt highet than this level. I did that test with mirror method. So, the conclusion should be more and more short PAL, Am I right?

How do you shoose the proper corridor lenght?

[essegn]

Mirror method is the correct one, but you have to also consider the following:

-wearer's habits
-previous progressive lenght corridor
-lens usage

read more here: http://www.optiboard.com/forums/show...orridor-length

[sharpstick777]

Add and distance powers are considerations too. The higher the add, the longer the corridor needed. High myopes want shorter corridors, hyperopes and oblique cyls longer. The general rule I use for seg min is: 2.50 =18mm 2.25=17.5mm 2.00 =17mm 1.75=16.5mm 1.50=16mm 1.00 = 15mm

[chip anderson]

Usually the progressive height is much more important than the length.

[SailorEd]

Call me "low tech" but for the last 2 1/2 years I've dispensed almost nothing but free form progressives. My current go to lens is the Seiko Surmount. It has corridors of 10,12, and 14. I use the 10 corridor for fitting heights of 15 (no, I don't go down to 14), to 19. 20 and above I use 12. I never use 14. In zyl frames sitting closer to the face, I use nothing but 10. Never have a problem. Patients are always happy. The proof is in the dispensing. If I use the Physio DRX, the short version from 15 - 19. Regular version 20 and above.

[Barry Santini]

Call me "low tech" but for the last 2 1/2 years I've dispensed almost nothing but free form progressives. My current go to lens is the Seiko Surmount. It has corridors of 10,12, and 14. I use the 10 corridor for fitting heights of 15 (no, I don't go down to 14), to 19. 20 and above I use 12. I never use 14. In zyl frames sitting closer to the face, I use nothing but 10. Never have a problem. Patients are always happy. The proof is in the dispensing. If I use the Physio DRX, the short version from 15 - 19. Regular version 20 and above.

I second this.

B

[Barry Santini]

Usually the progressive height is much more important than the length.

Well Chip...I might disagree, especially after playing with corridors for a while.

B