What To Use When….. Ken Kopp FCLSA Paragon Vision Sciences Paragon CRT RG-4 (Domestic only) CRT Dual Axis All are laser marked 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 • 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? 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 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 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 Data Topography Apical / Incomplete CRT or RG-4 Limbus-to-limbus Calculate elevation CRT Dual Axis 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 Data HVID • 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 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 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 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 Spherical CRT Elevation Difference Dual Axis CRT 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 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 Summary The decision to choose a specific design is best derived from; • Spherical CRT trial lens • • • Proper position Proper “bull’s eye” pattern Over-refraction Summary 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. Summary Can either the CRT, Dual Axis , or the RG-4 lens be the initial lens choice and ordered empirically? YES!! If you are not sure…contact your authorized Paragon CRT laboratory Thank you for your attention Questions?? Send email to; Your authorized CRT laboratory or [email protected]