Report 2010 - Interesting insights and perspectives
How much sense is there in correcting higher order aberrations? This was the question which Prof. Dr. Holger Dietze investigated and he presented his results as keynote speaker to an international audience as one of a series of top-class lectures at 11th MAFO - The Conference in Milan. For the third time in Milan now, leading figures from the international ophthalmic industry met one day before the Mido to hear the lectures and exchange ideas. This time the focus was on innovation, summed up by the question: “What’s new in ophthalmic optics?”
In the modern congress center at the futuristic trade fair ground of Rho Pero not far from Milan, this year again there was lively interest in the annual conference. Some of the 110 international visitors are regular attendants while others came for the first time to the event which is unique of its kind. The latest technology, daring predictions and critical statements – direct from the labs and from those in the vanguard of the industry – were presented.
The topics of the 13 international speakers from the USA, the Netherlands, Switzerland, Austria, Italy and Germany were divided up into three groups: ‘Lab Technology’, ‘Progressive Surfaces’ and ‘Lens Materials & Treatment’.
Lab Technology
Andy Huthöfer, President and CEO of National Optronics, started the Lab Technology session with a recommendation to businesses: Turn your production into a Profit Center! As head of your company, as well as delivering the best possible products you should always keep a constant eye on the economic side of the business. Once the prescription surface has been ground and the coating applied, for many manufacturers the profitable part is over. Edge machining, however, offers great potential and an opportunity to prove oneself a competent partner to ECPs, thus working profitably together. A modern and logical process chain with optimally integrated equipment is the secret to success according to Huthöfer. Often up to 75% can be saved in this area; in some companies this equipment pays for itself within half a year!
Here, too, the aim is to combine the best products with the best processes. And above all that means for modern spectacle frames, e.g. with high curvature, supplying perfect lenses. Huthöfer gave graphic examples of how remote edging can be integrated effectively in a company. In addition he discussed the prospect of edging ‘on the block’, i.e. edge machining of spectacle lenses while they are still attached to the plastic blocks which were presented at the Mido last year. This offers a whole range of advantages: The lens does not have to be removed from the block in a separate step, realigned, inspected and then re-blocked. Apart from this the whole lens surface is supported during grinding and a second clamping fixture during machining is unnecessary.
Welcome to the future
Wilhelm Anger, Lensbond developer and head of the company, began his talk with the provocative statement: “300 years of technological stagnation are enough! Welcome to the future”. Wilhelm Anger has been working in the optic industry for over 60 years and launched Optyl on the market in 1969; just one of many highlights in his long career. In Milan he showed the audience how spectacle lenses could be fixed without stress to the spectacle frame by adhesive bonding.
In the usual process of machining rimless spectacles by means of drilling & grooving, huge stresses and micro cracks occur around the drill hole. And this area inevitably remains the weak point of the glazed spectacles, according to Anger. Thus this interface needs to be joined in a different way, ideally by glueing. Adhesive technology is now well established in many areas of our daily life. Huge quantities of glue are used in the aircraft and automotive industries; modern joints are hardly imaginable without them. Thus why should spectacles be any exception?
Anger pointed out the advantages with regard to durability and above all the procedure of glueing spectacles. Through this new method of attaching lenses to spectacle frames, the join can withstand loads up to 130 N, according to Anger! An ECP can learn the procedure for mounting lenses in about two hours and is then able to equip a pair of spectacles ready for use in about ten minutes. Furthermore the investment required is fairly reasonable.
Lens thickness optimization
In the same group, Dr.-Ing. Bernd Freyermuth, CEO of LensWare Deutschland GmbH, talked about the possibility of a modern online control system for lens thickness optimization. Many advantages result from a technology which controls the calculation of lens thicknesses via a standard communication protocol between the customer data and the Web service. The separation of the analytic lens surfaces’ data generation and the lens surfaces´ data analysis for visualization is the key to this method.
Progressive Surfaces session
Dr. Markus C. Seraphim, Institute of Optics, was the first speaker in the Progressive Surfaces group. Accurate measurement over the whole surface of spectacle lenses is currently not possible without certain limitations. When projecting a pattern (deflectometry) onto the lens to be measured, the rear surface of the lens has to be blackened, in order to avoid interference which could otherwise falsify the measurements. In his well structured presentation, Dr. Seraphim showed in a very clear and understandable way the various possibilities and solutions for simplifying this operation and carrying out measurements directly in the production line.
In his talk, Dr. Dietmar Uttenweiler, Rodenstock, summarized the progress in individual spectacle lens technology over the past ten years. According to him, Rodenstock with its ‘Impression’ lens was the first to bring a lens of this kind onto the market; and today one can no longer imagine doing without this technology. More than 10 million lenses of this type have already been sold by Rodenstock alone worldwide. Simple CNC FreeForm grinding, however, is miles away from the highly sophisticated technologies for calculating, optimizing and producing truly individual spectacle lenses, according to Uttenweiler.
Jezus Cabeza, Carl Zeiss Vision GmbH, first took the audience on a short journey into the world of astronomy, in order to convey to his listeners the idea of an ideal point constellation. The subjective refraction is established and is a quite common approach to arrive at the correct spectacle lens prescription. If, however, one then takes into account the measurement of the wavefront by means of objective refraction, one gets to clearer and more exact results, according to Cabeza. Furthermore, using this method, local changes in refraction can be measured over the whole surface of the pupil, giving an insight into the quality of day and night vision. If we don’t hear from a customer who has been fitted with a new pair of spectacles with progressive lenses, then we know that everything is okay. However if the customer comes back to the shop and complains, it often seems that the customer himself is the problem. Often one tries to convince him that it is just a question of getting used to the new spectacles.
In his lecture, Bert-Elmar Pawlow, Technical & Development Manager at Hoya, discussed the different reasons for acclimatization problems with progressive lenses. The image deformation and ‘swim and sway’ effects, brought on by progressive surfaces, are not always equally serious. It is the orientation of the underlying distorsions which is most significant. Symmetry, too, is a decisive factor. Might it not be a good idea to try and stimulate the acclimatization problems in advance? Pawlow showed some of the possible solutions and their results.
Physiological limits to the correction of Higher Order Aberrations (HOA)
The MAFO team was fortunate to win Prof. Dr. Holger Dietze (Beuth Hochschule Berlin) as the main speaker on this topic. Partly contrary to modern measuring methods and to the contributions heard earlier, Prof. Dietze explained the limits to the correction of HOAs based on scientific studies. Modern techniques, based on aberrometry, show the extent and the kind of different HOAs that exist, the results promising more precise correction of defective visions. Custom-made spherical-cylindrical combinations in spectacle lenses should give their wearers improved vision. Dietze pointed out some well-known and some entirely new aspects of optical and neural image transmission. He backed these up with studies showing that the influence of HOAs on visual performance is quite small. Were we to assume purely theoretically that this correction would have a noticeable effect on visual performance, then there would still remain a range of factors which could have a limiting effect on the possible success. An example here would be the manufacturing tolerances of spectacle lenses. According to DIN EN ISO 8980 – 1, for spherical lenses these values are ± 0.12 dpt with an toroidal value of ± 0.09 dpt to ± 0.12 dpt depending on the strength. Thus the relevant value lies within the tolerance values permitted in spectacle lens manufacture.
Lens materials & treatment
The talk given by Dr. Philippe Pousaz (NGL Cleaning Technolog) was all about effluents in the optical industry which can cause substantial environmental contamination. In his remarks he showed that on the one hand an improved waste water policy in a company could protect the environment and on the other hand that recycling could save water and improve the quality of the product.
Dr. Federico Menta, Head of Development at Intercast, presented the latest developments in the manufacture of sunglass lenses. He also reviewed the development of phototropic and polarizing spectacle lenses and sunglasses and reflected on possible developments in the near future.
Dr. Willem Bos (Acomon AG) also discussed the topic of sunglass lenses and presented suitable lens materials. Here the same high standards should be applied for these materials as for corrective lenses. Despite changing fashions in color, clear vision should always be the highest priority. Furthermore high demands are also made on sunglasses with regard to physical properties.
How sunglass lenses can best be ‘semi-visibly’ engraved was made clear in the lecture by Gerold Simke (Laser 2000 GmbH). As well as discussing CO2 and Excimer lasers, he also described COX laser systems which are used today for this purpose, showing their respective advantages and disadvantages.
The presentation by Teodoro Tarantino (Cotec GmbH) was also about surface finishes. Under the catch phrase ‘slippery when dry’, Tarantino discussed the various highly sophisticated test methods used to measure surface finish and the technology behind hydrophobic and oleophobic spectacle lens surfaces.
This year’s choice of topics was met with general approval and the conference rooms remained full right to the end. By the way, top marks were awarded by the audience to Andy Huthöfer und Dr. Dietmar Uttenweiler for their excellent presentations. Also well received was the lecture by Professor Dr. Holger Dietze, particularly because of the absence of advertising and also because the listeners felt they could use the knowledge imparted in their own professional daily practice. The remarks by Dr. Markus Seraphim likewise got good marks for the lack of advertising. Finally the presentation by Jesus Cabeza was also very well received: Here, too, listeners could imagine making use of what they had learned in their own professional lives.
