Originally Posted by
Pete Hanlin
The primary value of a Bayer test pertains to manufacturing consistency- not as an indicator of overall product durability/quality. In other words, Bayer value is not particularly correlative with real-life durability, but it is a parameter which can indicate whether the manufacturing process is stable.
In the test, an uncoated CR-39 lens and the lens being tested are situated at the bottom of a container of either alum or "special" sand. The container is agitated for a number of cycles, the lenses are removed, and the amount of "haze" is measured on each lens (the CR lens is a reference). In the scale, a "1" indicates the value of an uncoated CR-39 lens, however, the scale is not linear (i.e., "6" is not twice as good as "3"). Bayer values are relevent for manufacturing managers (and apparently for some marketing managers).
Hoyalux iD uses a direct-to-surface process to create a front and back aspheric surface. Varilux Ipseo used to be created the same way (direct-to-surface process on front and back). Today, the front surface of a Varilux Ipseo is spherical, and the back surface is directly surfaced with an individual progressive design and distance power (this represents a refinement and advancement in the manufacturing process). Due to the fact that ophthalmic lenses are thin lens systems, the positioning of progression on one side or the other makes minimal difference to the wearer.
Of greater importance than marketing or manufacturing method is the performance of the design on a patient.
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