Results 1 to 19 of 19

Thread: Power distribution across a toric lens and prentice rule

  1. #1
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    Power distribution across a toric lens and prentice rule

    I've made this software for an article I've publish on an optics portuguese publication.

    Its purpose is to display the power distribution across the diferent axis of a lens and the prismatic power induce when the visual axis is decenter by a given distance and axis. (For example: when we read something at near distance, we converge and look down).

    Try it, it is free for non-comercial use.

    The autor isn't responsable for the improper or inadequate use of this software and disclaimes any responsability on its use. Use it only if your qualify for it and always interprete is results with professional judgement and caution.

    The software needs mschart.ocx, which was not included becaused of the uploads limits. See if it works.

    Visit www.contactologia.no.sapo.pt and see other optics software. I'll try to translate all of the software on that site to english, as soon as possible.
    Last edited by alberto_correia; 03-26-2007 at 08:16 AM. Reason: Removing old software version

  2. #2
    The Hi-End PALs Specialist Bobie's Avatar
    Join Date
    Nov 2005
    Location
    Thailand
    Occupation
    Optical Retail
    Posts
    381
    alberto_correia ,
    Please inform me , when you have English version in your website.
    You software not working with my PC and I don't know why.

    Thank :D
    " Life is too short to limit your vision"


    ISOPTIK : The Hi-End Eyeglasses Centre
    494 ERAWAN BANGKOK 4th floor
    Ratchaprasong , Bangkok , Thailand 10330
    isoptik@gmail.com
    www.isoptik.com
    Hotline & SMS : +66 81 538-4200
    Fax. : +66 2 251-3770

    :cheers:

  3. #3
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    Nice software, the version of prentices rule you use in your program falls apart when the power is very low and gies an error when computing a plano lens, but overall I love the graphics in it.
    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.

  4. #4
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    This particulary software supports both portuguese and english. Just run it and choose the language on the combo box in the window right side.

    If your meant the entire site, there is a easy way to do it. Simply enter the site link in the google translator. Give it a try, I did and I think it works just fine.

    If you meant the other software in the site, you'll be sure to tell about it. But there is no doubt I'll have some news soon.

    Alberto Correia APLO 22

  5. #5
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    Yes. I are right in deed. I'll sort it out and bring it back soon. It's an overflow error produce by a division by zero.

    It is also true that this short version of the Prentice rule, produces significant error when approaching plano power. Since it is the situation where less problems arises, I admit I was a bit lazy with my choice of this prentice rule.

    No problem. I'll fix it soon.

    Thanks

  6. #6
    The Hi-End PALs Specialist Bobie's Avatar
    Join Date
    Nov 2005
    Location
    Thailand
    Occupation
    Optical Retail
    Posts
    381
    Thanks , alberto_correia :cheers:
    " Life is too short to limit your vision"


    ISOPTIK : The Hi-End Eyeglasses Centre
    494 ERAWAN BANGKOK 4th floor
    Ratchaprasong , Bangkok , Thailand 10330
    isoptik@gmail.com
    www.isoptik.com
    Hotline & SMS : +66 81 538-4200
    Fax. : +66 2 251-3770

    :cheers:

  7. #7
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    Was it written in Visual Basic?

    Use the matrix form of prentices rule:

    Z = 2x1 prism matrix
    P= 2x2 power matrix
    h= 2x1 decentration matrix (in cm)

    Z=P*h

    Prismhorizontal = y * Dfront * sin A * cos A + x (Dsphere + Dcylinder * sin2 A)
    Prismvertical = y (Dsphere + Dcylinder * cos2 A) + x * Dfront * sin A * cos A

    the "y" would be the vertical drop (in cm) and the "x" would be the inset or convergence (in cm)
    Last edited by HarryChiling; 12-12-2006 at 01:04 AM.
    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.

  8. #8
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    It was written in VB6.

    Thanks for the equations. I'll exchange for these ones and post a new version here.


    Raul Alberto de Correia Sousa

  9. #9
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    Dfront stands for vertex distance (Dvertex) or lens front vertex power?

    Raul Alberto de Sousa

  10. #10
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    Dfront = front curve in diopters

    The vertex change compensation would be done before the power matrix.
    Last edited by HarryChiling; 12-20-2006 at 12:05 PM.
    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.

  11. #11
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    Gotta it.

    Thanks.

  12. #12
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    Hello.

    I finally had time to do some work with your equations.

    "A" is the difference between the cylinder axis and the decentration axis?

  13. #13
    ATO Member HarryChiling's Avatar
    Join Date
    Apr 2005
    Location
    Nowhereville
    Occupation
    Other Eyecare-Related Field
    Posts
    7,765
    A = axis
    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.

  14. #14
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    New software version

    Finally, the new version is ready.

    Many thanks to Harry Chilling for the equations.

    There are some small improvements on the different decentration input.

    Try it.

    Alberto Correia
    Last edited by alberto_correia; 03-26-2007 at 08:15 AM. Reason: Removing old software version

  15. #15
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    mschrt20.ocx

    In some cases, the program may ask for a specific file called mschrt20.ocx.

    This is a microsoft control that draws graphic chart and it is used by my program.

    Download it and copy/paste to c:\windows\system32 or to directory where the program is installed.
    Attached Files Attached Files

  16. #16
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22
    next
    Last edited by alberto_correia; 03-26-2007 at 08:18 AM.

  17. #17
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    New version od power distribution software

    Minor correction, when graphing lens power with zero spherical power.

    Enjoy.

    Alberto
    Last edited by alberto_correia; 04-03-2007 at 06:58 AM. Reason: Removing old software version

  18. #18
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    Question?

    Quote Originally Posted by HarryChiling View Post
    Dfront = front curve in diopters

    The vertex change compensation would be done before the power matrix.
    Someone pointed to me, that a -3,00x150 with a 10 mm downards (270 degrees) decentration and a 6 D front curve in the equations you send me, results in a Px +2,25, Py -2,60.

    Px is correct but Py isn't.

    So I went back and deducted the equations myself, following the matricial method you used.

    I'll present them in a equivalente power form (Sph Cyl x Axis):

    Px=x(Sph+Cyl*(sin A)^2)+y(-cyl*sin A *cos A)
    Py=x(-Cyl*sin A *cos A)+y(Sph+Cyl*(cos A)^2)

    This could be equal to yours equations if Dfront stands for front vertex power.

    Since the prism diopter is based on the assumption that the lens is placed in the prentice position, where the front surface is perpendicular to the incident ray, the prismatic decentration induced power shouldn't be dependent on this value.

    Could it be so?

    Cheers,
    Alberto Correia

  19. #19
    Bad address email on file
    Join Date
    Dec 2005
    Location
    Braga
    Occupation
    Optometrist
    Posts
    22

    New software version

    This new version is based on prentice rules equations deducted from the power matrix for a thin lens multiply by the decentration matrix.

    It assumes flat front curve perpendicular to the incident ray (prentice position). So, the results are in prisms diopters and not in centrad.

    Enjoy.
    Alberto Correia
    Attached Files Attached Files

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Thoughts on the economics of Interent Contact Lens distribution...
    By Barry Santini in forum General Optics and Eyecare Discussion Forum
    Replies: 7
    Last Post: 08-12-2006, 11:09 AM
  2. Your favorite toric/high myopia contact lens? Anything out there besides Coopervision
    By paulc in forum General Optics and Eyecare Discussion Forum
    Replies: 4
    Last Post: 06-07-2006, 06:36 PM
  3. Norville Lens Distribution The U.s.a.
    By WILLIAMFRANGE in forum General Optics and Eyecare Discussion Forum
    Replies: 2
    Last Post: 06-06-2006, 12:31 PM
  4. Toric lens rotating.
    By cookies in forum General Optics and Eyecare Discussion Forum
    Replies: 2
    Last Post: 04-29-2006, 02:17 PM
  5. Toric lens approved in Canada..................
    By Chris Ryser in forum General Optics and Eyecare Discussion Forum
    Replies: 0
    Last Post: 06-11-2005, 05:01 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