Results 1 to 24 of 24

Thread: Benefits of "digital" lenses for spherical patients

  1. #1
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693

    Benefits of "digital" lenses for spherical patients

    My optician asked a good question, and I think I gave the right answer. But I thought it would be a good brain exercise for Optiboard.


    Q: What is the benefit of "digital" designs for SV spheres? (No cyl, no add. Say, -1.00 DS, +1.00 DS, -6.00 DS, +4.00 DS)

  2. #2
    Master OptiBoarder
    Join Date
    Mar 2008
    Location
    Oakland, California
    Occupation
    Dispensing Optician
    Posts
    1,501
    [QUOTE=drk;554519]My optician asked a good question, and I think I gave the right answer. But I thought it would be a good brain exercise for Optiboard.


    Q: What is the benefit of "digital" designs for SV spheres? (No cyl, no add. Say, -1.00 DS, +1.00 DS, -6.00 DS, +4.00 DS)[/QUOTE

    As long as you hold your head real still, and look straight ahead through the OC, and don't use your peripheral vision, then no benefit at all.
    But then, under those circumstances, a pinhole would work pretty well also.

  3. #3
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    4,849
    Quote Originally Posted by drk View Post
    My optician asked a good question, and I think I gave the right answer. But I thought it would be a good brain exercise for Optiboard.

    Q: What is the benefit of "digital" designs for SV spheres? (No cyl, no add. Say, -1.00 DS, +1.00 DS, -6.00 DS, +4.00 DS)
    Compared to spherical/aspheric semi-finished or finished ± 1.00 DS, no difference due to inconsequential degrees of marginal astigmatism.

    There are incremental benefits over ±2.00 DS (generally more dioptric power = more optical error), especially when the values for tilt around the x-axis and y-axis increases, with or without non-default values (about 13mm) for vertex distance. The software must be capable of correcting for optical errors due to position of wear, non-optimal base curves, etc.

    Attempt to assess your client's tolerance for blur, on and off-axis. Use the more refined solution when in doubt.

    Why we don't want to use a spherical 1.67 index lens for a +6.00 DS Rx. That's in addition to 0.3∆ of chromatic aberration off-axis blur.
    Attached Thumbnails Attached Thumbnails +6.00 1.67.png  
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

  4. #4
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    I think you both are on a different track than I was thinking.

    I answered that it's "the same benefit" as we have come to expect from the older aspheric molded front lenses.
    a. if it's a low power lens, nada.
    b. if it's a higher plus, you get lens flattening.
    c. if it's a higher minus, you get minimal edge thinning (and we never cared much about that).

    I'm operating under the principle that aspheric lenses just correct the slop induced by using flatter front curves (for plus lenses).

    You guys are operating under the principle that off-axis viewing can be improved upon, compared to best-form spherical lenses.

    Both are right, I believe. Which do you think is a more fundamental consideration (i.e. the one that would compel you to use a good digital design for a high power sphere)?
    Last edited by drk; 07-23-2019 at 12:42 PM.

  5. #5
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    4,849
    Quote Originally Posted by drk View Post
    I think you both are on a different track than I was thinking.

    I answered that it's "the same benefit" as we have come to expect from the older aspheric molded front lenses.
    Not the same.

    a. if it's a low power lens, nada.
    Yup.

    b. if it's a higher plus, you get lens flattening.
    All powers would have flatter BCs. We'll probably have better results if we aphericize the meatiest curve, that is, the ocular curve for minus, and the BC for plus. But it's cost less to use spherical BCs working that back only, with a few exceptions.

    c. if it's a higher minus, you get minimal edge thinning (and we never cared much about that).
    A free-form generator can produce the asphericity on the back of a minus lens, with more effect than using a front apheric, where the BC is already pretty darn flat (+.50 to +1.00).

    I'm operating under the principle that aspheric lenses just correct the slop induced by using flatter front curves (for plus lenses).
    It also decreases magnification and minification, sometimes significantly. Maybe a decrease in vertex distance, depending.

    You guys are operating under the principle that off-axis viewing can be improved upon, compared to best-form spherical lenses.
    It can be close if the lens comes in narrowly spaced BCs, 1 D or slightly less, which is expensive to stock, and is unnecessary now that we can custom design a lens on a free-form platform. And if we need a slightly steeper or flatter BC, FF says yes, can do (software dependent).

    Note: Best form for hi-index lenses, without aspherisizing, results in very steep curves. For example, a +3.50 DS 1.67 requires a +10.25 BC, 1.74 index best form would be +12.25 BC. I doubt that most people on optiboard have seen a +12 base.

    Both are right, I believe. Which do you think is a more fundamental consideration (i.e. the one that would compel you to use a good digital design for a high power sphere)?
    Another example of FF superiority is with the aspheric pole/oc position. Semi-finished/finished requires the pupil heights to be lowered to align the optical axis with the center of rotation, not necessary with FF, minimizing vertical prism imbalance (when present due to dissimilar powers at ninety) with slightly less chromatic aberration to boot.

    If the lens has optimizations beyond aspheric's/atoric surface designs, we should expect slightly better visual performance at all angles of gaze, depending on the degree of power and tilt. For example, -5.00 DS wrap 10˚ panto 10˚, -4.62 -0.25 x 46 .25∆ BI needs to be surfaced to match the prescribers intent.

    Best regards,

    Riobert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

  6. #6
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Hmm...a lot to digest.

    I will be back for mansplainin' sometime soon! :)

  7. #7
    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
    Join Date
    May 2000
    Location
    Seaford, NY USA
    Occupation
    Dispensing Optician
    Posts
    5,778
    Quote Originally Posted by Robert Martellaro View Post
    ...to match the *prescribers intent.*”
    WOW! Now there’s a loaded and obfucacious term.

    If anyone can, with confidence, ascertain this by looking at a typical Rx, more power to you.

    B

  8. #8
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    4,849
    Quote Originally Posted by Barry Santini View Post
    WOW! Now there’s a loaded and obfucacious term.

    If anyone can, with confidence, ascertain this by looking at a typical Rx, more power to you.

    B
    I've been listening to politicians so much lately that I'm beginning talk like them.
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

  9. #9
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    A free-form generator can produce the asphericity on the back of a minus lens, with more effect than using a front apheric, where the BC is already pretty darn flat (+.50 to +1.00).

    I didn't consider that. So, free form SV for minus can have a bit more of an edge thinning effect than the old molded ones. Huh. Generally FFSV is not expensive, but I do wonder what kind of numbers we're talking. 0.5mm? (I know, dependent on the variables.) But are we talking 1 mm in many cases, or "chump change"?


    It can be close if the lens comes in narrowly spaced BCs, 1 D or slightly less, which is expensive to stock, and is unnecessary now that we can custom design a lens on a free-form platform. And if we need a slightly steeper or flatter BC, FF says yes, can do (software dependent).

    So...when we order, say, Walman's house FFSV (or even VSP's Unity), are we going to get dual-digitally-surfaced-from-puck, or are we going to get it from a semi-finished blank? What goes on, out there?

    Another example of FF superiority is with the aspheric pole/oc position. Semi-finished/finished requires the pupil heights to be lowered to align the optical axis with the center of rotation, not necessary with FF, minimizing vertical prism imbalance (when present due to dissimilar powers at ninety) with slightly less chromatic aberration to boot.


    This is news to me, as well. I am probably guilty of ordering FFSV with a 3mm drop-below-pupil-center MRP, instead of a "fitting height". Dang. As a flaming myope with 1.67 PALs, I don't like looking 4mm above the PRP due to standard PAL fitting procedure. I get aberration, and find myself tilting my head back with distance viewing for better optics. (I fit myself high to help offset this.) But SV patients (and anisometropes) would greatly benefit.

    But what about this whole "optic axis intersecting the center of rotation of the eye" thing? Is that just for a sphero/cylinder lens and it merely "averages" the worse optics between straight-ahead gaze and downgaze? Does this mean that FFSV can compensate for optics on downgaze without compromising the straight ahead gaze?

    If the lens has optimizations beyond aspheric's/atoric surface designs, we should expect slightly better visual performance at all angles of gaze, depending on the degree of power and tilt. For example, -5.00 DS wrap 10˚ panto 10˚, -4.62 -0.25 x 46 .25∆ BI needs to be surfaced to match the prescribers intent.
    IOW, you're saying that one of the nice things about FFSV is automatic POW compensation. Yeah.
    Last edited by drk; 07-30-2019 at 02:04 PM.

  10. #10
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Quote Originally Posted by Barry Santini View Post
    WOW! Now there’s a loaded and obfucacious term.

    If anyone can, with confidence, ascertain this by looking at a typical Rx, more power to you.

    B
    Typical Barry.

    Simply put (and you know this), the numbers on the Rx pad is the "prescriber's intent". No more, no less. It's not mysticism.

  11. #11
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    4,849
    Quote Originally Posted by drk View Post
    I didn't consider that. So, free form SV for minus can have a bit more of an edge thinning effect than the old molded ones. Huh. Generally FFSV is not expensive, but I do wonder what kind of numbers we're talking. 0.5mm? (I know, dependent on the variables.) But are we talking 1 mm in many cases, or "chump change"?
    About 3% to 5% more (compared to front aspherics) according to D. Meister's Optical Analysis program. A tad more for high minus (>8 D), without lenticulation.

    So...when we order, say, Walman's house FFSV (or even VSP's Unity), are we going to get dual-digitally-surfaced-from-puck, or are we going to get it from a semi-finished blank? What goes on, out there?
    Puck, semi-finished, same animal. Although the blank might have been formed in digitally generated mold, it's a stretch to call it dual FF/digital. That talk is for the marketing dept.

    This is news to me, as well. I am probably guilty of ordering FFSV with a 3mm drop-below-pupil-center MRP, instead of a "fitting height".
    Pupil height. Take 'em on all RXs except spherical ±0.50 D. It's good practice, minimizes VI and other aberrations, and only takes a minute or so to measure on a preadjusted frame. Lower the OC .5mm per one degree of panto tilt for non-optimized lenses, aligning the lens axis with COR.

    Dang. As a flaming myope with 1.67 PALs, I don't like looking 4mm above the PRP due to standard PAL fitting procedure. I get aberration, and find myself tilting my head back with distance viewing for better optics. (I fit myself high to help offset this.) But SV patients (and anisometropes) would greatly benefit.
    That's not right. 4mm shouldn't generate enough CA at this power. Try a 1.60 refractive index in the same package to rule that out. If you were anyone else I'd suspect overminusing or a hyperopic shift.

    But what about this whole "optic axis intersecting the center of rotation of the eye" thing? Is that just for a sphero/cylinder lens and it merely "averages" the worse optics between straight-ahead gaze and downgaze?
    Probably better optics at all angles of gaze.

    Does this mean that FFSV can compensate for optics on downgaze without compromising the straight ahead gaze?
    More better, with the best software, keeping in mind that FF generators can make "dumb" lenses also.

    IOW, you're saying that one of the nice things about FFSV is automatic POW compensation. Yeah.
    It places the OC on the primary gaze, without compromise, over a wide range of tilt and wrap values. Si.

    Best regards,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

  12. #12
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Quote Originally Posted by Robert Martellaro View Post
    About 3% to 5% more (compared to front aspherics) according to D. Meister's Optical Analysis program. A tad more for high minus (>8 D), without lenticulation.
    I'm trying to be clear, and make sweeping generalizations.

    If you're saying 5% more than a little, then I'll just neglect this.

    Puck, semi-finished, same animal. Although the blank might have been formed in digitally generated mold, it's a stretch to call it dual FF/digital. That talk is for the marketing dept.

    So if they're going to do a FFSV, you're saying they choose a "puck" with an approximate certain base curve? And then surface the front and the back?



    Pupil height. Take 'em on all RXs except spherical ±0.50 D. It's good practice, minimizes VI and other aberrations, and only takes a minute or so to measure on a preadjusted frame. Lower the OC .5mm per one degree of panto tilt for non-optimized lenses, aligning the lens axis with COR.
    Agree there. Specify for everything to be consistent. But dropping for panto on FFSV not needed?

    That's not right. 4mm shouldn't generate enough CA at this power. Try a 1.60 refractive index in the same package to rule that out. If you were anyone else I'd suspect overminusing or a hyperopic shift.
    It's true. I now know that I'm too picky for high index. It's mid-index for me.
    Thanks!

  13. #13
    Master OptiBoarder OptiBoard Gold Supporter
    OptiBoard Silver Supporter

    Join Date
    Mar 2012
    Location
    Maryland
    Occupation
    Dispensing Optician
    Posts
    2,002
    remember molded minus aspherics usually have at least
    .5 mm difference in center thickness compared to surfaced lenses, and often 0.8mm less. Unless FFSV is including some lenticularization it generally will not be thinner than radially aspheric molded lenses. But there are so many other peripheral vision benifits. My current main pir is molded aspheric though

  14. #14
    Master OptiBoarder AngeHamm's Avatar
    Join Date
    Apr 2010
    Location
    Richmond, VA
    Occupation
    Optical Retail
    Posts
    1,905
    Quote Originally Posted by Robert Martellaro View Post
    Pupil height. Take 'em on all RXs except spherical ±0.50 D. It's good practice, minimizes VI and other aberrations, and only takes a minute or so to measure on a preadjusted frame. Lower the OC .5mm per one degree of panto tilt for non-optimized lenses, aligning the lens axis with COR.
    Somewhat off topic, but taking a pupil height also reinforces to the patient that they need more than just a generic PD to get properly fitted glasses. I measure OC height on every patient for this reason.
    I'm Andrew Hamm and I approve this message.

  15. #15
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Jul 2008
    Location
    Cincinnati
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    536
    Quote Originally Posted by AngeHamm View Post
    Somewhat off topic, but taking a pupil height also reinforces to the patient that they need more than just a generic PD to get properly fitted glasses. I measure OC height on every patient for this reason.
    Help me out here. I do a height with my Ray ban googles polar suns -1.50 ou with a 48 mm vertical, height is +/- 40 mm. When I look down at my golf ball height is now+/- 20 mm. I now have 3.0 diopters base up prism. Now what?

  16. #16
    Master OptiBoarder optical24/7's Avatar
    Join Date
    May 2006
    Location
    Tx.
    Occupation
    Dispensing Optician
    Posts
    5,322
    Quote Originally Posted by Don Gilman View Post
    Help me out here. I do a height with my Ray ban googles polar suns -1.50 ou with a 48 mm vertical, height is +/- 40 mm. When I look down at my golf ball height is now+/- 20 mm. I now have 3.0 diopters base up prism. Now what?
    1. You would be looking through yoked prism looking down. No harm, no foul.

    2. You made a bad frame choice when you got a frame with your pupils sitting 8mm from the top of the frame.

  17. #17
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    4,849
    Quote Originally Posted by drk View Post
    I'm trying to be clear, and make sweeping generalizations.

    If you're saying 5% more than a little, then I'll just neglect this.
    Keep in mind that the difference in thickness due only to refractive index between 1.60 and 1.67 is only ((1.60 - 1.00) / (1.67 - 1.00) = 0.90) 10% thinner.

    So if they're going to do a FFSV, you're saying they choose a "puck" with an approximate certain base curve? And then surface the front and the back?
    As stated, it's semi-finished, meaning molded front, surfaced back.

    Agree there. Specify for everything to be consistent. But dropping for panto on FFSV not needed?
    Unless otherwise specified by the lens manufacturer, we should bisect the corneal reflection in the primary gaze. The software takes it from there.

    It's true. I now know that I'm too picky for high index. It's mid-index for me.
    Thanks!
    Your welcome. Ditto on the chroma sensitivity, although I'm a few diopters less minus than you. Our only saving grace is possibly higher IQs, and we're the goto folks for splinter removal.

    Best regards,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

  18. #18
    Master OptiBoarder optical24/7's Avatar
    Join Date
    May 2006
    Location
    Tx.
    Occupation
    Dispensing Optician
    Posts
    5,322
    Quote Originally Posted by Robert Martellaro View Post

    Your welcome. Ditto on the chroma sensitivity, although I'm a few diopters less minus than you. Our only saving grace is possibly higher IQs, and we're the goto folks for splinter removal.
    It’s true, Myopes test higher on most I.Q. Tests. But counter-research ( optical24/7 research think tank...) shows Hyperope’s are more out going, have more friends, get invited to more parties and are generally better looking than Myopes...

  19. #19
    OptiBoard Apprentice
    Join Date
    Jun 2016
    Location
    Australia
    Occupation
    Dispensing Optician
    Posts
    20
    Quote Originally Posted by optical24/7 View Post
    It’s true, Myopes test higher on most I.Q. Tests. But counter-research ( optical24/7 research think tank...) shows Hyperope’s are more out going, have more friends, get invited to more parties and are generally better looking than Myopes...

    I guess that explains myself with my emmetropic Rx with a mild add. I am a "special" cave troll :(

  20. #20
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
    Join Date
    Oct 2016
    Location
    Maryland
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    849
    Hey, what about us mixed astigmatic presbyopes? I feel left out!
    I bend light. That is what I do.

  21. #21
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Quote Originally Posted by Don Gilman View Post
    Help me out here. I do a height with my Ray ban googles polar suns -1.50 ou with a 48 mm vertical, height is +/- 40 mm. When I look down at my golf ball height is now+/- 20 mm. I now have 3.0 diopters base up prism. Now what?
    Don, your golf buddies called.

    They said your golf game problems are not measured in millimeters. They said they should be measured in 100s of yards.

    JUST SAYIN'

  22. #22
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Attention all Optiboarders. Attention all Optiboarders.

    We have a paradigm shift (for me).

    You know how PALs are branded? I don't say "hey, patient, you need a PAL" I tend to get a little more geeky than that, and will discuss the brand, etc. Let them understand the sciency-nature of what we do. These aren't generic. "Hey, man, you're wearing a (insert brand here) progressive with digital design (whatever) with blah, blah, blah.

    Well, if you think about it (and Robert's correcting me in that we just measure a fitting height/POW, and the computers do the rest) that these FFSV are pretty dang high-tech, too; in the vicinity of PALs.

    I'm going to prescribe and promote them as such.

    So the answer to my optician to the original question will now be: "Optics, baby. Optics!"

    Am I behind the curve on realizing this?

  23. #23
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Jul 2008
    Location
    Cincinnati
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    536
    Quote Originally Posted by drk View Post
    Don, your golf buddies called.

    They said your golf game problems are not measured in millimeters. They said they should be measured in 100s of yards.

    JUST SAYIN'
    Not when your putting

  24. #24
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,693
    Then you have a weird putting stance. You don't need to stand tall at address, like with your driver. Put that head down, man!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. "EyeMed Policies" Patients MUST sign BEFORE order is placed...
    By Uncle Fester in forum General Optics and Eyecare Discussion Forum
    Replies: 5
    Last Post: 02-06-2014, 03:59 PM
  2. Looking for suggestions on "freebies" to hand out to patients
    By ozerman in forum General Optics and Eyecare Discussion Forum
    Replies: 45
    Last Post: 10-26-2012, 04:42 PM
  3. Replies: 1
    Last Post: 05-18-2012, 06:56 AM
  4. Patient "sees" concentric rings wearing digital progressive
    By edk68 in forum General Optics and Eyecare Discussion Forum
    Replies: 14
    Last Post: 03-16-2012, 10:22 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
OptiBoard is proudly sponsored by:
Younger Optics and Vision Equipment