Objective
Evaluate and measure accurately the dioptric power of progressive addition ophthalmic lenses at specific points on the progressive
addition lens surface with interferometry, by using a Twyman Green interferometer, and correlate the results with those taken from an
Auto-focimeter (TOMEY TL-100).
Method and materials
The progressive addition ophthalmic lenses were inspected, using a Twyman Green interferometer at specific points, and interference
patterns were acquired and processed, obtaining the dioptric power that theses lenses presented. Comparison of the respective results was
conducted with those taken from an Auto-focimeter (TOMEY TL-100) in order to check if the two types of measurement are
interchangeable, and statistical analysis was carried out for both types of measurements on the spherical and the cylindrical component of
the measurement.
Results
The analysis showed, that the two methods, Interferometry (Twyman Green) and Auto-focimeter (TOMEY TL-100) are correlated. The
plotting for both measuring techniques were similar. From the statistics and especially the p-values taken showed that the two measuring
techniques do not different significantly. Also the Bland and Altman plot shows that there is a difference of about 0.30 Ds for the
spherical component while it was about 0.17 Dc for the cylindrical component between the two methods. With interferometry it was
difficult and time consuming to get as many measurements as those taken with the Auto-focimeter due to the manual and laborious nature
of the technique.
Conclusions
A Twyman-Green interferometer was set to measure progressive addition ophthalmic lenses. The results showed that it is possible to
measure such type of lenses although interferometry it was difficult and time consuming to get as many measurements as those taken
with the Auto-focimeter due to the manual and laborious nature of the technique.
Abstract
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