We selected 25 pairs of progressive power lenses from 5 companies(lO pairs from
higher price group brands and 15 pairs from lower price group brands) among higher
domestic market share products and investigated whether they met tolerances
regulated by...
We selected 25 pairs of progressive power lenses from 5 companies(lO pairs from
higher price group brands and 15 pairs from lower price group brands) among higher
domestic market share products and investigated whether they met tolerances
regulated by the Organization for Intemational Standardization(ISO). The range of far
area focal power was from -2.50D to -3.00D and addition power was from + 2.00D
to +2.50D.
The average error from far area focal power was 0.17:!:0.091D(higher price group
: 0.15:!:0.095D, lower price group: 0.19土0.086D). 3 out of 25 pairs met tolerance by
ISO(:!:0.12D in 20.00D and s6.00D) which was very low(12.0%), 까le average
unwanted cylinder power was 0.15:!:0.060D(higher price group: 0.15土0.065D, lower
price group: 0.16:!:0.058D). 4 out of 25 pairs met tolerance by ISO(:!:0.12D in 20.00D
and sO.75D) which was also very low(16.0%). The average error from addition
power was 0.08:!:0.073D(higher price group: 0.06土0.043D, lower price group:
0.10:!:0.085D). 18 out of 25 pairs met tolerance by ISO(:!:0.12D in s4.00D)(72.0%).
For thickness, we could not evaluate comparing to ISO standard because the
manufacturer did not specify the nominal value. It should not deviate from the
nominal value by more than :!:0.3 mm by ISO standard. The average thickness was
1. 77土0.187 mm(higher price group: 1.74:!:0.049 mm, lower price group: 1.80:!:0.237
mm). The higher and lower price groups and right and left lenses were significant
statistically in focal power, unwanted cylinder power, addition power and thickness(p
< 0.05). From these measurements, we found only 1 pair of progressive power
lenses(B-25-20 in higher price group) which met tolerance regulated by ISO.
To meet ISO tolerances, more precise manufacturing process should be
considered.