View Poll Results: Which error impacts acuity the most?

Voters
26. You may not vote on this poll
  • Not specifying Rx in precision of 0.12D

    3 11.54%
  • HOAs not being optimized

    8 30.77%
  • Testing acuity at 20 feet

    11 42.31%
  • Congratulating a client when there's little change Rx

    4 15.38%
Page 2 of 2 FirstFirst 12
Results 26 to 30 of 30

Thread: Which matters more:?

  1. #26
    Just An Optician jediron1's Avatar
    Join Date
    Mar 2004
    Location
    USA, New York
    Occupation
    Dispensing Optician
    Posts
    1,727
    Quote Originally Posted by chip anderson View Post
    Adding artificial tears may give you a refraction for when artificial tears are in place only. Patient's tears may not be as thick or as smoothe.
    Don't take much in corneal radius to change Rx.

    Chip


    Chip I think you hit upon something. As you said tears may give you a refraction but is it the right one? Tears also may change a refraction if you don't believe me put a drop of tears plus or systane. ( I know systane is used primarily for dry eye's ). When you look up you will be completely blurred until a few blinks or I even have had patients take up to 2 minutes before they said their vision is clear. With artificial tears your adding another medium for light to pass through and doing so can effect the response of the patient if enough time has not been allowed for the tears to pass.

    just my take

  2. #27
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    I am amazed and shocked by the number of people picking HOA's.

    Not specifying Rx in precision of 0.12D = Defocus or Astigmatism 1st order
    HOAs not being optimized = Spherical Aberration, Coma, Marginal Astigmatism, Curvature of Field, and Distortion 3rd order
    Testing acuity at 20 feet = 20ft is the equivalent of 6m which is 1/6 = 0.16D of vergence entering a lens from the start Defocus 1st order
    Congratulating a client when there's little change Rx = smallest increment of change that could be present is a change of 0.00 -0.25 which has a spherical equivalent of 0.12D Defocus 1st order.

    With exception to HOA's the rest are directly related to first order errors. I choose congratulateing the patient on very little change in Rx and the reason is because: This has a psychological effect on the patient, they may have come into the office because they noticed that their vision has deteriorated and when the prescriber tells them that the change isn't significant they may be discouraged from correcting their vision or worst upset that their vision isn't correctable. I think the better approach is to trial frame in this scenario to let the patient see the difference between the old and new and make their own assumptions as to what is significant. Of course as far as amount of error goes the testing distance is the most significant since 20ft introduces more error than the others combined.

    Now the reason why I don't think HOA's are as significant is because it seems that it has become an industry buzz word used amoung the marketing guru's in our industry to convince the masses that it is significant and I believe it is, but not to the extent in which every one seems to think. Corrected Curve is used to minimize the aberrations that can be minimized.

    ALL THE SEIDEL ABERRATION AR E DIRECTLY RELATED TO ONE ANOTHER. YOU MINIMIZE ONE AND YOU WILL AMPLIFY ANOTHER SO CHOOSE WHICH ONE YOU WILL CORRECT WISELY.

    Spherical Aberration - the form and the stop size or pupil in ophthalmic optics has a significant effect on this error, since the pupil is small and uses a reletively small area of a lens at any one given time this error is not really significant enough for many lens desingers to minimize at the expense of other aberrations.

    Coma - This is an aberration that is present off axis. I like to refer to it as spherical aberration off axis.

    Marginal Astigmatism - this is the difference between the sagittal and tangential powers off axis, when teh difference between these two powers off axis becomes greater than the astigmatism in the prescription patient will notice this fast. Correct choice of spherical curves or use of aspherics to compensate comprimises in spherical curves will correct fro this aberration.

    Curvature of Field - The eye's far point sphere is flatter than the Petzval suface which is where the focal points of a lens fall when the marginal astigmatism has been corrected this difference between the far point shere and the petzval surface is what creates what's known as curvature of field or power error.

    Distortion - this aberration is due to the loss and gain in magnification between minus and plus lenses off axis. The effect is pincushion or barrel distortion. Does this necessarily have an effect, yes the images produced are skewed, but they are in focus. When this distortion is corrected the lens is said to be orthoscopic from greek "ortho" meaning straight and "scopic" meaning to see, to see straight.

    By choosing the correct design lens which is often done by looking at a chart the manufacturer provides with their lenses the lab or optician can make sure that the lens is meeting the designers objective which is often one of a few things:
    1. Minimum Distortion
    2. Minimum Tangential Error
    3. Minimum Off Axis Astigmatism (in all it's flavors)
    Spherical aberration and Coma are often not a huge issue as the pupil size restricts it's effects, so we're left with a choice of reduction between marginal astigmatism, curvature of field, and distortion.

    Technically we could throw Chromatic aberration in the mix as well in it's two forms longitudinal and transverse, but the design has very little effect on these and choosing the right material for the Rx is the best way to minimize this aberration.
    1st* HTML5 Tracer Software
    1st Mac Compatible Tracer Software
    1st Linux Compatible Tracer Software

    *Dave at OptiVision has a web based tracer integration package that's awesome.

  3. #28
    Banned
    Join Date
    Jun 2000
    Location
    Only City in the World built over a Volcano
    Occupation
    Dispensing Optician
    Posts
    12,996

    Sure it was....

    The .12 diopter standard was abandoned because, practioners, labs, manufactures got too lazy and found it too high a standard to be held to.
    Had nothing to do with the inacurracy of refraction.
    Just as you will find 95% of cylindrical axis(es) at 5 degree intervals, some practionsers only seem to shoot for 10 degree intervals. It isn't because this is the best that can be done. It's just all the effort the practioner want's to put in. In the old days many prescribers would go 1/2 a degree on thier refractions.
    I have had practioners tell me I only refract to 20/20 if they can see better than that I don't bother with trying for it.
    We just got lazy and sloppy and we aren't trying to do any better unless some gadget will do it for us.
    What's the use of wave front, bi-toric and the like if the Rx isn't derived as accurately and as precise as possible. Other than getting a higher price for the product that is.

    Chip

  4. #29
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    Quote Originally Posted by chip anderson View Post
    The .12 diopter standard was abandoned because, practioners, labs, manufactures got too lazy and found it too high a standard to be held to.
    Had nothing to do with the inacurracy of refraction.
    Just as you will find 95% of cylindrical axis(es) at 5 degree intervals, some practionsers only seem to shoot for 10 degree intervals. It isn't because this is the best that can be done. It's just all the effort the practioner want's to put in. In the old days many prescribers would go 1/2 a degree on thier refractions.
    I have had practioners tell me I only refract to 20/20 if they can see better than that I don't bother with trying for it.
    We just got lazy and sloppy and we aren't trying to do any better unless some gadget will do it for us.
    What's the use of wave front, bi-toric and the like if the Rx isn't derived as accurately and as precise as possible. Other than getting a higher price for the product that is.

    Chip
    When I worked as a COA I had on occasion refracted a patient and every phoropter I worked on had axis's in 5 degree steps it was my discretion what axis I would pick between the 5 degree steps and it was not very difficult to narrow it down, but I know for a fact that when our OMD taught us we would refine cyl's in 15 degree steps then 5, this is where most the techs would stop and the OMD was supposed to refine further from there, but often as they got comfortable with our work they would just sign and date the Rx and off they went. Since I filled in as a tech and worked as an optician in the office I would refine from 5 degree steps by splitting the difference and then using my discretion which from their for instance:

    if the patient JCC and they liked between the 5 and 10 I split the middle and flipped again, if the patient liked between the 7.5 and 10 then I woud go with 8, if there was history I would go with which ever degree 8 r 9 that was closest to the original Rx or K's. Would I ever write 7.5, NO, if I got a 7.5 I knew why but if i got an 8.5 I knew it was BS. If you look at ANSI for fabrication degees would leave a 4 degree area to fall within on a hgiher cyl which was fine for me since I was also fabricateing. If I wasn't also the optician there I would probably be just as azy as all the other techs and write in 5 degree steps and skip refineing. I think more importantly than cylinder refinement was the fact that often the techs never balanced the Rx, some wouldn't even refine the sphere. They would establish sphere power, cylinder axis, cylinder power and then they assumed that the OMD would take it from there. Refraction is an area that coud be imporved but I think the weakest link in the chain is numb nuts optician that have no clue what they are doing.
    1st* HTML5 Tracer Software
    1st Mac Compatible Tracer Software
    1st Linux Compatible Tracer Software

    *Dave at OptiVision has a web based tracer integration package that's awesome.

  5. #30
    Master OptiBoarder
    Join Date
    Sep 2006
    Location
    Kansas
    Occupation
    Dispensing Optician
    Posts
    2,203
    Quote Originally Posted by chip anderson View Post
    The .12 diopter standard was abandoned because, practioners, labs, manufactures got too lazy and found it too high a standard to be held to.
    Had nothing to do with the inacurracy of refraction.
    Just as you will find 95% of cylindrical axis(es) at 5 degree intervals, some practionsers only seem to shoot for 10 degree intervals. It isn't because this is the best that can be done. It's just all the effort the practioner want's to put in. In the old days many prescribers would go 1/2 a degree on thier refractions.
    I have had practioners tell me I only refract to 20/20 if they can see better than that I don't bother with trying for it.
    We just got lazy and sloppy and we aren't trying to do any better unless some gadget will do it for us.
    What's the use of wave front, bi-toric and the like if the Rx isn't derived as accurately and as precise as possible. Other than getting a higher price for the product that is.

    Chip
    I don't agree. 95% of the scripts I see are to the nearest degree. I'm just as likely to see an axis of 123 as I am 125. The good thing about self-referring drs is that when you have to eat the redo, you are careful with the refraction.
    I know you see Rxs from a different set of Drs. I guess that is how they see 50 patients/day.

    Specifying to the 0.5 degree is BS. The patient can't be that precise, the refractionist can't either and the glazer can't either. An axis of 121.5 + 2.0 is ridiculous.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Why Federal Debt Matters
    By For-Life in forum Just Conversation
    Replies: 4
    Last Post: 09-27-2007, 02:46 PM
  2. 2007 GREAT NEW JOBS from I matters!
    By imatters.net in forum The Job Board
    Replies: 0
    Last Post: 11-22-2006, 11:26 AM
  3. I matters job oppportunites
    By imatters.net in forum The Job Board
    Replies: 0
    Last Post: 08-11-2006, 09:41 AM
  4. Employment help from I matters
    By imatters.net in forum The Job Board
    Replies: 0
    Last Post: 09-22-2005, 06:07 PM

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
  •