Progressive Addition Lenses (PALs) Sheedy JE. Progressive Addition Lenses – Matching the specific lens to patient needs. Optometry 2004;75(2): Sheedy JE. Correlation analysis of the optics of progressive addition lenses. Optom Vis Sci. 2004;81(5): Sheedy JE, Campbell C, King-Smith E, Hayes, JR. Progressive powered lenses - the Minkwitz theorem. Optom Vis Sci, 2005;82(10): Sheedy JE, Hardy RF, Hayes JR. Progressive addition lenses - measurements and ratings. Optometry 2006;77:23-39.

Progressive Addition Lenses (PALs) n Alternative to bifocals or trifocals n Advantages –Cosmetic –Functional n Patient preference Distance Intermediate Aberrations Near

Vision with bifocal compared to PAL One continuous world Distance and near are connected Vision is more “natural” Narrow areas of clear vision Areas of distortion in world Wide areas of clear vision Distance and near worlds are separated. Unusable visual space between them Image jump

The Minkwitz Theorem n Perpendicular to the vertex line, the astigmatism changes twice as quickly as the rate of change of power along the vertex line. Minkwitz vG. Uber den flachenastigmatismus bei gewissen symmetrischen aspharen. Optica Acta 1963;10(3):223-7

Hard vs. Soft Designs … …

Rotlex instrument

Lens Acquisition n 12 lenses provides good reliability while still being logistically feasible n 23 lens designs were ordered in pairs from six different laboratories –Attempt to avoid getting lenses from the manufacturer made in the same batch –Rx: Plano distance power and near add All ordered in CR-39, except Rodenstock AT and VE Illumina which were only available in PolycarbonateAll ordered in CR-39, except Rodenstock AT and VE Illumina which were only available in Polycarbonate –Thanks to: Walman Optical, Minneapolis, Minnesota; Diversified Ophthalmics, Cincinnati, Ohio; Hoya Vision Care, Cleveland, Ohio; Interstate Optical, Mansfield, Ohio; Optical One Inc., Youngstown, Ohio; Select Optical, Columbus, Ohio; Toledo Optical, Toledo, Ohio; and Top Network, Columbus, Ohio

Data acquired n Mean scaled results

Data Analysis n Distance viewing zone n Intermediate viewing zone n Near viewing zone n Unwanted astigmatism Distance Intermediate Aberrations Near

Task analysis Distance Intermediate Near

Ratings Criteria for calculating ratings from measured values Rating CategoryDerivative Measures0-100 scale Distance Zone 50% - width at fitting cross 5-20 mm 50% - area from 1.5 mm above fitting cross mm 2 Intermediate Zone 50% - width at 1.25 D add2-5 mm 50% - area from 0.75 to 1.50 add mm 2 Near Zone* 50% - width at Y0-15 mm 50% - area to Y +0.5 mm mm 2 AstigmatismLargest magnitude D * Near zone ratings reported for a specified fitting height. Fitting height determined by adding 2 mm to the Y value

Summary

Which PAL should be used? n There are literally an infinite number of possible designs n There are many, many designs in the market from which to choose. n The information provided by manufacturers is inconsistent and nearly impossible to compare

Premises n Significant differences exist in the optical characteristics of the various PALs n These differences affect the size of the field of fixation for distance, intermediate and near vision. n Patient lifestyle characteristics are a factor in determining patient PAL design preference

n Member –Vision Ease n Affiliate Members –Lens Crafters –Shamir Insight –Carl Zeiss Vision –J&J Spectacle Lens Group n Supporting groups –Optical Laboratories Association –COLTS laboratories

Collaborators n Charles Campbell n Ray Hardy n John R. Hayes n Chunning Huang n Matt Helfrich n Ewen King-Smith n Priya Ramamoorthy n Allan Yi n Karl Citek n Bret Andre