Lens testing throughout production

To offer effective varifocal lenses, Essilor puts the wearer at the heart of a five-step process, called the dioptric loop. Optical testing is part of every stage of this loop.

1. Collection of physiological data: the visual function of each 'test-wearer' is studied to enable Essilor to draft specifications that are compliant with the nature of the 'test-wearers' vision.

2. Optical design: the wearers' physiological data is converted digitally using an optical computation program with successive optimisation.

3. Prototype manufacturing: test lenses are custom-made using several sophisticated technical steps.

4. Measurement check: advanced checking instruments enable reliable and precise lens testing. The optical properties and parameters are checked in the lab.

5. Optical testing: the test-wearers try out their lenses. To ensure their full wearer satisfaction, the tests are conducted using the double-blind technique and the test-wearers are asked precise questions,to analyse both their objective and subjective impressions of the lenses.

There are two possibilities at the end of this loop:

- the test-lens is satisfactory: it is released for sale

- the lens test is not conclusive: the researchers start their work again from the beginning.