I have noticed that some progressive designs such as Intouch and Definity seem to give some extra plus / reduced minus several mm ABOVE the distance reference point???
I have noticed that some progressive designs such as Intouch and Definity seem to give some extra plus / reduced minus several mm ABOVE the distance reference point???
I have noticed this for some Autograph III's and S-Fit's. Which makes sense, seeing as they are compensated Rx. But I know InTouch is not compensated, so that perplexes me. Not sure about Definity though, I don't dispense that lens a whole lot.
I thought this thread would get more comments....anyone........Bueller?
I checked various Shamir and Zeiss lenses waiting to be delivered, including my eyeglasses, and they all show the correct power at and above the distance reference point. Two possibilities: 1) You're working with lenses that fall in the very soft category that position some of the unwanted astigmatism above the 180 line, including above the DRP. The Definity would fall in that category, as well as the Hoya iD/Mystyle, the latter depending on the design choice. 2) You're seeing blur due to chromatic aberration as you move the lens away from the prism reference point. However you said that the power changes, not that the mires become blurred, so I would rule out #2.Originally Posted by ak47
Hope this helps,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Thanks Robert...#1 seems likely...and I believe I have seen this on some Hoya ID in the past. Out of curiosity, were any of the Shamir lenses you looked at Intouch?
No. An Autograph 3 (add +2.25) and Spectrum (+3.00). The Zeiss lenses were Individuals (2N and Balance) and a Pure 19mm, all Trivex. Powers were from low plus, to my -3.00 -2.00 x 90 add +2.25 Rx.
If we want wider and/or smoother blur boundaries around the corridor, it can only be done by lengthening the corridor and/or distributing the unwanted astigmatism, the optical junk so to speak, above the 180 line. An acceptable compromise for some folks, mostly for those emerging presbyopes and moderate to high hyperopes.
Best regards,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
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