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Summary of Contents for Paragon CRT Dual Axis
- Page 1 Paragon CRT Dual Axis ® Quick Reference Guide...
- Page 2 (Image A). Some corneas that appear spherical may also manifest a peripheral corneal elevation difference. The Paragon CRT® lens design has a fixed chord length of 8 mm (6 mm treatment zone surrounded by a 1 mm return zone width).
- Page 3 RZD and LZA may be varied in the second meridian to compensate for the peripheral corneal slope meridional differences of an eye. In other words, when fitting a Paragon CRT Dual Axis® design, the BC remains constant throughout the treatment process, unless there is a need to correct untreated or residual power.
- Page 4 5. Repeat the measure 180 degrees away in the elevated area opposite the first elevated measurement. 6. Calculate the average difference from the elevated areas to the shallow areas. 7. If the average difference is: • less than 30 microns, a Paragon CRT Dual Axis® lens may not be indicated.
- Page 5 • between 25 to 30 microns, consider prescribing a one-step (25-micron) increase in RZD. • between 31 to 60 microns, consider prescribing a two-step (50-micron) RZD difference. • between 60 to 90 microns, consider prescribing a three-step (75-micron) RZD difference. •...
- Page 6 In such cases, a three-step, 75-micron or four-step, 100-micron meridional difference in the RZD may be indicated. Image D When fitting Paragon CRT Dual Axis®, use this chart to determine the variation of RZD or LZA in conjunction with the average elevation differences. If the Average...
- Page 7 (8.90/550 & 600/-33 & -34). 4. Over-refract for the appropriate BCR and order the final Paragon CRT Dual Axis® lens. It is of critical importance that the desired meridian is identified relative to the shallow and deep RZD meridians.
- Page 8 Consider use of the two RZD difference (50-micron) design when these indicators are present. The indication of the Paragon CRT Dual Axis® design is confirmed if the treatment zone becomes more circular, flexure is eliminated, lens centration is improved, circumferential landing is observed, and the targeted treatment is achieved.