What to use when
1 / 20

What To Use When….. - PowerPoint PPT Presentation

  • Uploaded on

What To Use When…. Ken Kopp FCLSA Paragon Vision Sciences. Paragon CRT CRT Dual Axis. All are laser marked. RG-4. (Domestic only). Paragon CRT. Patented design using Proximity Control Technology Certification necessary/up to -6.00 with up to -1.75 D of astig.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' What To Use When…..' - marla

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
What to use when
What To Use When…..

Ken Kopp FCLSA

Paragon Vision Sciences

Paragon crt crt dual axis
Paragon CRT CRT Dual Axis

All are laser marked


(Domestic only)

Paragon crt
Paragon CRT

  • Patented design using Proximity Control Technology

  • Certification necessary/up to -6.00 with up to -1.75 D of astig.

  • Calculated from flat K and spherical manifest

  • 10.5 mm diameter is most often used/range from 10.0-12.0 mm

  • LZA has no radius of curvature

  • 100 lens DDS or SureFit options (domestic)

Paragon crt dual axis
Paragon CRT Dual Axis

  • This design mimics the shape of the astigmatic cornea by RZD and/or LZA manipulation without changing the BC (Proximity Control).

  • Based on the average elevation difference between the flat and steep meridian

  • FDA approval indication remains the same as the spherical product. Up to -6.00 D with or without up to -1.75 D of astigmatism

  • No certification necessary

  • Diagnostic sets of 16, 40 or 80 lenses

When do i use which design
When Do I Use Which Design?

The CRT DDS should be the “go-to” tool for all reshaping candidates. It will be the design of choice to trial for proper centration, tear patterns, and correct BC selection.

When do i use which design1
When Do I Use Which Design?

The pre-treatment data is a “clue” as to what option choices you may need.

  • Flat K and spherical manifest

  • Pre-treatment topography

  • Refractive vs. Corneal astigmatism

  • HVID

  • Fissure and/or abnormal pupil size

Patient pre treatment data
Patient Pre-treatment Data

Flat K and Spherical Manifest

  • Flatter (<42.00 D) and steeper (>45.00) corneas can be more difficult to achieve proper centration and complete treatment.

    Options – RG-4 or CRT

  • Higher myopes (>5.00 D) most often take longer to achieve stable VA and may need to treat in two steps.

    Options – CRT or CRT Dual Axis depending on elevation differences

Patient pre treatment data1
Patient Pre-Treatment Data


Limbus-to-limbus -

Calculate elevation

CRT Dual Axis

Apical / Incomplete

CRT or RG-4

Patient pre treatment data2
Patient Pre-Treatment Data

Refractive vs. Corneal Astigmatism

  • More refractive than corneal = uncorrected astigmatism (ROL)

  • More astigmatic correction than spherical component - not a desirable candidate

  • Corneal astigmatism approaching 2.00D will require a deeper sag (RZD/Mean K) choice initially. CRT DA/CRT/RG-4

Patient pre treatment data3
Patient Pre-treatment Data


  • Average HVID is 11.8 mm

  • Larger diameters than 10.5 mm may be required to improve centration or aid patient comfort

  • Smaller diameters may be necessary for HVID of <10.8 mm

    CRT – 10.0 to 12.0mm, CRT DA – 10.5 & 11.0 mm, RG-4 = 10.0 to 12.4

Patient pre treatment data4
Patient Pre-treatment Data

Fissure and Pupil Size

  • Asian fissure size and lid structure can determine diameter choice

  • Larger pupil size (> 6mm ) in normal illumination can result in flare/glare issues

  • Insertion/removal difficulties can determine design choice

    CRT/CRT DA/RG-4 have fixed 6 mm OZ

Design choices
Design Choices

CRT – Spherical

  • With DDS, trial for all reshaping candidates.

  • Make necessary parameter adjustments for

    proper positioning or edge lift appearance

  • Over-refract to determine the proper BC

  • If the desired position, “bull’s eye” pattern, edge lift and ROL are satisfactory – dispense and follow-up.

Design choices1
Design Choices

If the spherical CRT trial shows an incomplete “bulls eye” pattern or does not center properly…consider CRT Dual Axis

Spherical CRT

CRT Dual Axis

Incomplete apical elevation difference
Incomplete/Apical Elevation Difference

Spherical CRT

Dual Axis CRT

Crt dual axis
CRT Dual Axis

Elevation difference

  • RZD difference depends on the calculated average elevation difference between the flat and steep meridian (pre-treatment)

  • RZD difference can range from 25 to 75 microns

  • LZA can also be altered in either meridian to adjust edge lift

    appearance – 2 degree maximum

  • If elevation data is not available, a default of 50 micron RZD difference with single LZA is chosen.

  • Observe trial lens or order with calculated/default RZD

Design choices2
Design Choices

Without DDS trial option

  • Order CRT with *SureFit or normal warranty depending on pre-treatment criteria

  • If the Flat K is below 42.00 D or above 45.00 D and the spherical manifest is below -5.00 D, consider RG-4 first.

    * SureFit has limited parameter specifications and only available in the US


The decision to choose a specific design is best derived from;

  • Spherical CRT trial lens

    • Proper position

    • Proper “bull’s eye” pattern

    • Over-refraction


If the CRT Trial lens does not display proper centration or incomplete “bull’s eye” pattern;

  • Consider Dual Axis design based on elevation differences of the flat vs. steep meridian (from elevation/height map)

  • Consider RG-4 for flatter corneas (<42.00 D) or steeper corneas (>45.00 D) or when the CRT design is no longer manageable.


Can either the CRT, Dual Axis , or the RG-4 lens be the initial lens choice and ordered empirically?


If you are not sure…contact your authorized Paragon CRT laboratory

Thank you for your attention


Send email to;

Your authorized CRT laboratory or [email protected]