Analysis of the technical quality of freedom sale lens with reference in presbiopye patients’ ophthalmic lenses

Abstract

The nonprescription lenses, industrially manufactured, are acquired in different places, without prior knowledge of their quality and without the guidance of qualified personnel. <em><strong>Objective:</strong></em> to establish the optical quality of nonprescription lenses. <em><strong>Methods:</strong></em> we used 50 nonprescription eyeglasses, which were elected for each patient in choosing the correction with which they felt more comfortable for her work in next vision. After use by 15 days of the lenses described, is by contrast material in ophthalmic lenses CR-39 and the prescription, used the same time. By building a refractometer, it was determined the focal length and the index of refraction, obtaining the number ABBE and reflectance. We measured power of posterior index, thickness and density Sagita. <em><strong>Results:</strong></em> with regard to power, the patient is always inclined to choose the nonprescription lenses with greater increases in order to seek magnification, showing that patients are overcorrect, plus signs of the power of these lenses, not accounted for 40% of the cases. The average density of the nonprescription lenses was 1.18 g/cm3, the index of refraction 1560 and an average number ABBE average of 30. Conclusions: Because of these characteristics lenses are less thick, less weight, more chromatic dispersion that lenses reference CR-39.