Rodenstock, my Entry into the Spectacle Lens Business.
At the end of the 1970s Rodenstock was number 2 on the world market of spectacle lens optics together with Essilor. The world leader was AOC (American Optical Corporation) a US company strongly concentrated on the US market and on mineral lenses. The Rodenstock product portfolio included spectacle lenses, frames and ophthalmic optical instruments. The head of the research and development sector, as well for spectacle lenses as for ophthalmic optical instruments was Dr. Günther Guilino, one of the most prominent scientists in the ophthalmic optics industry. He was looking for a scientific associate with the perspective representing him for part of his functions at the lens development department. As we had the intention to stop our itinerant life and to settle down a world famous big company like Rodenstock seemed to be a solid base. My application was accepted and from 1977 on I was a member of the Rodenstock team for the development of spectacle lenses.
My first major task was a simple field investigation to determine the night driving capability of photochromic spectacle lenses. During the 1960s the US company Corning Glass Works invented the photochromic mineral glass material which darkened when exposed to sunlight. In the evening when the intensity of the daylight decreased, the photochromic lens became clear again. Now one important legal issue was, if the return to the clear state was fast enough to allow driving a car in twilight conditions. It was not possible to simulate the natural conditions in a laboratory so the test had to be executed as a wearer test. 5 photochromic lens types had to be tested and compared under different weather and environment conditions. From mild weather in the city of Munich to the low temperatures of an excursion by cable car to the summit of the Zugspitze. All these different conditions had to be tested to certify the lenses for night driving.
As one spectacle consists of two lenses one test wearer was not enough and to cover the different weather conditions in a reasonable time also weekend measurements were necessary. I needed a reliable and flexible assistant. My wife agreed and so, equipped with several frames, mounted with different photochromic lens types, a luxmeter and a mobile transmission measuring device we spent many hours walking around and analyzing the darkening and clearing of the different lenses, always under the curious observation of people. The results allowed us to support the launch of the newly developed brand Colormatic 2 as the first real night driving compatible photochromic lens.
The top priority Rodenstock project however was the development of the first progressive lens of German origin. The German industry was a reference for the ophthalmic optics business in the world and particularly for the German optician. Therefore the introduction of the progressive lens by the French manufacturer Essilor in the 1960s and 1970s under the trade name Varilux met with scepticism by the German market and had to face resistance by certain German scientific experts. Nevertheless some opticians attracted by the technical challenge and higher margins took the risk to try this new type of lens. The second generation of Varilux proved its superior benefits for the wearer and became an increasing success on the market. The Varilux lens was distributed by Ehinger, which later became an Essilor subsidiary and the second biggest German manufacturer, Carl Zeiss. So Rodenstock, the German market leader, urgently needed its own product and started to promote the product Zoom from BBGR, an Essilor daughter. Zoom however was a lens of the first generation and could not compete with Varilux 2. So Rodenstock decided to start a development project for their own progressive lens. The man in charge was Dr. Rudolf Barth, a physicist who developed the design concept of the variable periodicity and, together with the manufacturing experts at Regen, the production process based on modern CNC machines.
When I arrived in 1977 at Rodenstock the theoretical mathematical preparations were practically finished and Guilino and Barth concentrated on the final design optimization and the drafting of the patent. Parallel to the design optimization I was in charge of the physiological analysis of the new lens and the preparation of the adaptation by the optician. This included in particular measuring the optical distortion and the visual acuity across the lens surface , the development of the centering recommendations and centering devices and finally the evaluation of the visual comfort of the wearer with wearer tests. These wearer tests were comparing the new lens Progressiv R, with the major lenses of our competitors based on the double blind test principle, i.e. at the moment of the interview neither the wearer nor the person examining the wearer using a questionnaire knew the special lens type worn by the test person. In order to obtain statistically reliable data more than 100 persons participated at the test. After more than 2 months testing there were 2 remarkable results : First the overall assessment of Progressiv R was better than for all the competitive lenses tested and second the wearers appreciated particularly the aberration-free far vision part. This was a major point for our marketing strategy. Varilux 2 which was the prototype of the modern progressive lens was conceived as a totally aspheric lens design which substantially improved the comfort and the adaptation of the progressive lens. One less favorable characteristic was that in the far vision periphery the lens geometry showed a surplus of positive optical power. To compensate for this Essilor recommended, at least in Germany, some systematic corrections for the far vision and near vision power, when ordering the lens, which complicated the work of the optician. So we positioned the Progressive R as the refraction correct lens, a progressive lens needing no power adjustment when ordered. This was a very definite and as the launch showed successful marketing position for the first progressive developed in Germany to attack the French leader.