Any tips?
Any tips?
Usually just go with half the B on most frames, I don't see a need to take an OC because they won't be looking through that part of the lens when reading. If they are intermediate SV glasses I will take an OC.
If the frame isn't too deep, I'd put it a mm or two above center. If it's a deeper frame, take an OC approximating LOS to reading material.
I'm Andrew Hamm and I approve this message.
2-3 mm below center for the down gaze, if even needed.
I bend light. That is what I do.
For single vision on higher powers I'll dot the sample lenses with a marker and have them hold the reading material at the position they prefer then adjust from there where the OC will need to be. I don't find complaints with where the OC's are in general as any prism is yoked so I usually on a 3.00 diopter power or less will just keep it om the mechanical center.
For bifocals I take 2 short strips of cellophane tape (tab over one end for easy removal/adjustment) put them on the sample at guesstimated height of the seg line and have them simulate their gaze and adjust from their feedback.
I'm getting confused, again.
1. The title of the post is "fitting high for reading glasses". Wouldn't that be "fitting low for reading glasses"?
2. If lenses are not low-powered, as most reading glasses typically are moderate-powered, I can see trying to optimize optics in downgaze. (Or, less commonly, if there is anisometropia, trying to minimize prismatic imbalance on downgaze.)
3. But here's where my brain blows a gasket. With standard pantoscopic tilt, which has the goal of making the back of the lens the same distance from the eye in straight-ahead and down gaze, you have to correct by moving the optical axis of the lenses down approximately 1mm per degree tilt (which should be about 5-10 degrees) so we get the best optics/least aberrations in both major eye positions (straight ahead and down). (<---Please feel free to correct me on this.)
So...how do we improve on this evening-out method? In other words, can we say "hey, these are reading glasses, designed for downgaze--the heck with straight-ahead gaze"?
And if we do attempt to do that, what kind of pantoscopic tilt would be best, then? The same amount? I say it depends solely on the geometry, and that the geometry would not change. The optical axis will still need to intersect the center of rotation of the eye, always.
Assuming this is true, I believe there is only one position of the optical centers that would be correct for that pantoscopic tilt: the same old 3-4mm drop from pupil center in straight-ahead gaze that we always use.
Is this correct?
(And don't get me started on Lensgrinder's reminder that our base curve choices for near-vision optics is different than base curve choices for far-vision optics...)
Last edited by drk; 02-03-2021 at 03:17 PM.
Thank to all.
@Drk sorry my English is not perfect, for me fitting high ="optical center vertical position" down or up from the datum line.
I have the same doubts..... I have see "tablet centration device" they can take a photo when the client is reading text on the tablet itself.
I see some optician use a mirror when the client is reading a text or take the far oc position and they calculate how to down it (I dont' know the formula)
Usually I take (with some difficulty and lack of precision) the vertical oc when client is stand up and reading a page of a book (I have to sit on a chair) Now I simply put che oc 2mm down
I may be in left field on this, but shouldn't the near pd be involved in this equation, since our eyes converge as we look down to read, also, the OC would depend on frame and rx. When custom making near vision only I spot the pupil with the frame in normal position then have them slide the frame down their nose, as they should look over the top for anything they may need to look at at a distance, and check to see if their gaze of vision in that position is relatively the same. I also take into account if they simply just give the grandma look over the top with the glasses in normal position.
Roy W. Jackson, Sr. ABOC
Lots of tech discussion for OC’s on readers! My advice, 1. Take near PD. 2. Order lenses. 3. Go have a beer...
folks wear readers all over their nose, up, down, crooked. Powers are usually close so vertical prism is yoked. No harm, no foul.
No! Life must be more complicated than that.
Seriously I just treat SVNO like SVDO, but use the near PD.
Actually, I am indeed confused. I need to make the best of the situation.
Maybe Derek and the Martellaros will run in and ease my worried mind.
Last edited by drk; 02-04-2021 at 01:17 PM.
@Drk okkkkk
@Quig Ok maybe is a silly thing but for improving.... think a question and get answer, we are technician we have to do the best we can or wallmart will steal our jobs...best regards
Fitting high?
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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