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Verifying and evaluating progressive addition lenses in clinical practice
1drgbell@pacbell.net
Optometry (St. Louis, Mo.)
|May 8, 2001
Summary
Clinical verification of progressive addition lenses (PALs) is crucial. This study found premium and non-premium PALs performed similarly, with significant inconsistencies across brands and notable improvements in maximum astigmatic distortion over time.
Area of Science:
- Ophthalmology
- Optometry
- Optical Engineering
Background:
- Progressive addition lenses (PALs) constitute over 50% of multifocal lenses in the US.
- Existing clinical verification methods for PALs are inadequate.
- Automated lensmeter techniques offer a simplified approach to PAL verification.
Purpose of the Study:
- To present a simplified method for clinical verification of progressive addition lenses.
- To compare the performance of premium-quality versus non-premium-quality progressive lenses.
- To assess variations in lens characteristics across different brands.
Main Methods:
- Thirty pairs of progressive lenses were analyzed using a modified Humphrey 330 Lens Analyzer.
- Fifteen pairs were classified as 'premium-quality' and fifteen as 'non-premium-quality'.
- Five key criteria were measured: Distance Zone Width (DZW), Intermediate Zone Width (IZW), Near Zone Width (NZW), Drop Distance (DD), and Maximum Astigmatic Distortion (MAD).
Main Results:
- No significant difference in performance was found between premium and non-premium progressive lenses.
- Considerable product inconsistency was observed within every brand tested.
- Zone size variations were substantial and appeared across all tested brands.
Conclusions:
- Performance characteristics of premium and non-premium PALs are comparable.
- Significant variations in zone sizes exist, irrespective of lens quality or brand.
- Improvements in Maximum Astigmatic Distortion (MAD) have been noted since 1986, with specific lenses showing potential benefits for certain frame types.