Digital varifocals and buying a suit
Wednesday, 8 July 2015 | Direct Specs
Let's compress fifty odd years of the history of varifocal optics in a few paragraphs and use buying a suit as an analogy to help us understand where varifocals are at today.
It might not be immediately obvious, but there's an almost infinite number of permutations when it comes to specifying the power and fitting positions for varifocals and to all intents and purposes, every pair of varifocal glasses is unique.
The One Size Fits All Suit
For many years, varifocals were only available in an 'off the shelf' form; lens manufacturers would make 'semi-finished' lenses to a fixed design and the optician's lab would finish the lens with the customer's prescription. Although the lens power would be precisely what was required, the overall design of the lens and the quality of the image produced was less than perfect. For the majority of wearers that system worked well enough, even though people weren't getting the optimal solution for their particular prescription - sometimes very far from it.
Different Chest and Trouser Sizes
A couple of decades ago, some manufacturers introduced 'modular designs', where the most suitable lens form could be selected from a few different designs. Choosing this type of lens meant customers would get a lens that was much closer to the ideal but still a 'halfway house' to the perfect pair.
Suits You Sir
'Digital varifocals', where every pair is made to an optimal design for each individual customer, have been available for a few years. Although commonly called 'digital varifocals', this is short-hand for 'digitally surfaced varifocals' - i.e. the machinery that creates the final lens surfaces is computer controlled. Essentially this is the equivalent of the tailor-made suit where every aspect of the product is customised to the individual concerned. You might even see these lenses described as 'tailor made' or 'custom made'.
Bizarrely these lenses do have a downside for some people - those who have been wearing varifocals for years may have become so used to the distortion and limitations of their lenses that they find having a totally personalised design can really throw them, at least to begin with. However, once someone gets used to digitally surfaced lenses, they really won't want to go back to the older 'boilerplate' designs.