Measurements of Progressive addition lenses with interferometry

Abstract

Evaluate and measure accurately the dioptric power of progressive addition ophthalmic lenses at specific points on the progressive addition lens surface with interferometry, a Twyman Green interferometer was used, and correlate the results with those taken from automated focimetry. Also progressive addition ophthalmic lenses were measured in order to have a complete presentation of the power distribution and the performance of these lenses. 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. Results: The data showed, that the two methods Auto-focimeter and Interferometry (Twyman Green) are correlated. The plotting for both measuring techniques were very similar, although the measuring points were not numerical the same. From the statistics and especially the p-value its time taken showed that the two measuring techniques do not different significantly. Also from the Bland and Altman plot it 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: An alternative method is provided based on interferometry. More specific 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