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pp.173-182
We selected 25 pairs of progressive power lenses from 5 companiesOO 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 International StandardizationOSO). 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±0.086D). 3 out of 25 pairs met tolerance by IS0(±0.12D in ;::.:o.OOD and ~6.00D) which was very low02.0%), The average unwanted cylinder power was 0.15±0.060D(higher price group: 0.15±0.065D, lower price group : 0.16±0.058D). 4 out of 25 pairs met tolerance by IS0(±0.12D in ;::.:o.OOD and ~0.75D) which was also very low(16.0%). The average error from addition power was 0.08±0.073D(higher price group : 0.06±0.043D, lower price group : 0.10±0.085D). 18 out of 25 pairs met tolerance by IS0(±0.12D in :<=:4.000)(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± 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 statistica!ly 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.
