Purpose:
The following information will assist you in processing Kodak Precise Progressive 1.56 EvoClear Lenses.

SUMMARY OF CHANGES:
The base curve selection chart has been modified.

General:
Standard surfacing procedures for CR-39^®progressive lenses should be used with the Kodak Precise Lens, but bear in mind that 1.56 EvoClear has a refractive index of 1.557. If you have questions regarding these lenses, contact Technical Services at 800-759-0075.

Computer Calculation of Rx:
The easiest, most efficient method to calculate and process values for an Rx is to use an existing computer software package that contains Kodak Precise Lens design data. If your software company has not included this data in its package, our Technical Services group will be happy to provide the necessary specifications. Please forward us the contact name and phone number of your software vendor. If you need a software program for processing lenses, Signet Armorlite has developed a computer program to calculate surfacing data. This program is available through Signet Armorlite's Technical Services Department.

Layout:
All surfacing should be done in relation to the prism reference point located on the 180° line. We recommend that you block the lens on the prism reference point even though the corridor is decentered 3 mm. If blocking is done on the geometric center of the blank, you must calculate the amount of decentration prism needed to move the optical center to the prism reference point. The fitting cross is located directly above the prism reference point dot. This improves the accuracy of positioning the patient's pupil to the center of the corridor. If you use an automated lens blocker, such as the Gerber Step-One System, and if you are blocking on the cross, be sure to use a segment placement on the lens blank of 4mm down.

Semi-Visible Markings:
Kodak Precise Lens markings have a "+" at the nasal and temporal sides along the 180† axis line. Approximately 3mm below the nasal "+" you will find the "K₊I" product code. Approximately 3mm below the temporal "+" you will find the add power of the lens. These marks can be located by visually inspecting the lens. Position the lens at arm's length, preferably in front of an overhead fluorescent light. Slowly move the lens away from the edge of the light fixture while looking at the estimated location of the marks along the surface of the lens. The marks will become visible at a given angle of light.

Removal/Re-marking the Temporary Reference Marks:
The Kodak Precise Lens markings may be removed by wiping the surface with alcohol, acetone, or standard lens mark removing solvents. These marks are designed to withstand all processing procedures. They provide an easy way to verify the edging accuracy and can be removed before or after tinting.

To re-mark the lens, first locate the semi-visible markings, specifically the "+" symbols engraved along the 180† axis line (see above procedure for locating the semi-visible marks). Once you have located the semi-visible markings, dot them on the lens and use the Kodak Precise verification chart for the final re-marking.

Fining and Polishing:
Processing the 1.56 EvoClear Lens is similar to the CR-39 lens material. Safety bevel the lens before fining to alleviate chips and allow the slurry smoother access along the lens surface. Large lap tools (at least 3 inch) should be used and allowance made for approximately 0.3mm of stock removal. We strongly recommend fining pads with eight or more petals be used for curves over 9.00 diopters. This can prevent flares and wrinkles.

Edging:
Layout for edging should be done in reference to the fitting cross located 4.0mm above the MRP. The fitting cross is placed at the point of the specified segment height and monocular PD.

AR Coating:
Multi-layer AR coatings can be applied to Kodak Precise Lenses. Because lens impact resistance is reduced by AR coatings, we recommend a 1.6mm minimum center thickness and a backside coating that will enhance the impact resistance capability. Be sure that your AR coating is compatible with your backside coating. Include impact testing for lenses AR coated and sold by your lab. It may be necessary to increase the minimum center thickness in order to meet impact resistance requirements. Please call Technical Services at 800-759-0075 for additional information about coatings and impact resistance.

Tinting:
The 1.56 EvoClear Lens material tints similarly to other high index lenses using the normal materials and methods. After tinting, clean the lenses with alcohol or acetone to remove excess dye from surfaces. If you decide to tint the lens, test a sample lens first.

Neutralizing:
Our test results show the KODAK Precise 1.56 EvoClear Lens can be damaged when using tint neutralizers designed for CR-39. Use a neutralizer designed for polycarbonate or high index materials.

Fitting and Frame selection:
The fitting point (+) has been positioned slightly higher than our other progressives. Therefore, you can fit the lens at the center of the pupil rather than at the bottom of the pupil. Always use monocular PDs and individual fitting heights when they differ more than 1.0 mm.

We recommend a minimum fitting height (sometimes called the segment height) of 20 mm. While a successful fitting of Precise lenses is possible with less than a 20 mm fitting height, we recommend the KODAK Concise^™ short corridor lens for smaller fitting height situations.

The frame shape, frame PD and patient's PD affect how much of the full addition reading area falls inside the frame. To insure these variables will not limit near vision, lay the frame (with the fit point marked) onto the KODAK Lens Dispensing Aid (part number K763-578.) Check to see if the blue shaded area is contained within each eye of the frame. This chart also references a recommended minimum distance up from the fitting point to the frame edge. We advise a minimum distance viewing area of approximately 12mm for patient comfort.