Boosting understanding amongst the entire practice team about what happens in the optical lens manufacturing process was a keynote lecture which drew a packed audience to the OSA stand at 100% Optical. Keith Elliott, Hoya Regional Sales Manager for the North gave an inspired CPD accredited presentation drawing on his own experiences of a career in lenses.
He highlighted some of the issues which can occur, and explained how they happen – particularly when the same prescription is requested by the patient but the lens does not provide the same optics: “It may be related to the frame fitting differently, vertical, and horizontal centration compared to the previous glasses. Decentration, when the frame pd and patient pd do not align, is also an issue to guard against, particularly on higher prescriptions,” he explained.
Keith ran through the importance of frame selection for different frame choices, especially high prescriptions, and issues with the supra groove when glazing rimless frames.
He took delegates through the journey from how semi-finished lenses are made with details of polymerisation and the curing process of seven hours for Trivex lenses and 72 hours for 1.67 index lenses.
The many stages of manufacturing for optimum lenses – sometimes with up to 0.01dioptres of accuracy – included preparing the lenses for processing with labelling and marking up, taping for protection, blocking with cadmium-free alloy or, in some cases, wax.
“Then the real work begins in taking away the bulk of the unwanted lenses known as cribbing, moving to the finer processes of surface generation, often with dual surface optimisation.”
The finishing processes of smoothing and polishing – sometimes a diamond finish – are followed by the coating department’s work. This highly skilled stage, often carried out by technicians with decades of experience, includes tinting and hard coatings, plus multi-anti-reflection coatings, known as MAR.
Delegates were interested to hear the history of anti-reflection coatings having started in 1886 and accelerated in importance during the demands of second world war combat. Keith ran through the stages of glazing – sometimes completed at the practice – and stressed the value of having a hand edging device as part of the in-practice toolkit.
Keen to dispel some of the hype around the much-used term of “freeform generated lenses”, Keith stressed that the end product will only be as good as the data and technical specification programmed into the lens generator – be warned!
Anyone interested in joining a lab tour around the country should contact the OSA office for details mmacritchie@osa-uk.co.uk
