It is a fine line dividing, often one that is barely discernable, between genius and madness. Launching a new lens design can sometimes be not dissimilar especially in this new era of free-form progressive designs. Just a little software tweak in the wrong direction can turn positive wearer feedback into negatives.
The most notable benefit of high definition free-form lens design, think of 40,000 hinge points on a 70mm lens surface has been the outcome almost overnight to override 100 years of patent lens design around spherical and toroidal lens curves. Tscherning, Percival, Whitwell, Ostwalt, Wollaston and Tillyer to name but a few. In our modern age of instant expectation the huge significance of free-form lens production has been swiftly passed over without due recognition to its genius. Aberrations that affected lens designs for generations effectively vanished overnight.
One of the most successful recent new lens design launches (like 20 years recent) has been the degressive lens. Here we have a single vision two focus lens for those whom need a reading addition to help their focus for close but need a little less plus for intermediate viewing achieved with an upper minus or rather lesser plus area. These vocational SV lenses are indispensable. Try being a 60-year-old plumber or painter wearing bifocals or progressives. No wonder such tradespersons traditionally retired early – they could not see at work.
Indeed I recall my earliest dispensing suggestion as a teenage spectacle wearer was to suggest to my hairdresser struggling with stiff neck muscles in his new pair of NHS bifocals (38mm solids) to go back to his optician and ask for an up-curve lens design (purely selfish – I did not wish to lose an ear).
So the degressive single vision reading Rx with reducing power in its upper was soon complemented by Booster (anti-fatigue in Essilor speak) a single vision distance prescription boosted by a small addition in its lower portion, again another two focus lens design. Although both from their original low almost decimal point lens additive powers some seem now to be creeping into the realms of full additions +1.00 and over into the world of bifocals or progressive. The demarcation lines becoming rather blurry.
So one would have thought that these two now covered all SV eventualities. Well it seems now we obviously did not envisage some inventive Spanish ophthalmic software team conjuring up a third option. Single Vision with an upper night myopia spot. While the theory that one’s night vision becoming less focussed due to widening pupils so requiring a stronger correction than would be the case in sunny day time is well recognised. Nothing other than a modified Rx second pair for twilight driving could previously address this. Also it would appear night myopia is more prevalent the younger the viewer. So now we can offer a third supercharged single vision option this time with modified upper distance. That user’s eye can now seek out the extra -0.25 distance focus spot, hence our choice of AFAR as its descriptive name. So back to the header title will this new lens prove to be as successful as its other two older specialised SV siblings, as ever an outcome only time will tell.
However, it is possible the AFAR design could turn out to be a rather more fascinating story around this question. ‘Has this lens design a part to play as a myopia control spectacle lens?’ While the role of contact lenses in myopia control seems relatively well documented that for spectacle lenses more resembles pea soup. The extremely long gestation period for any meaningful outcomes does not help. Depending whether the optical theory of all round more plus at the lens periphery as opposed to a specific area of segment addition occasionally with a spoonful of prism is considered the preferred route. Using AFAR design but centring at the pupil centre (ie drop by 8mm). Remember the ‘B’ measurement of spectacle frames are always the lesser excepting round shapes so most should fit from a 70mm lens blank. Reducing -0.25 from the prescribed Rx should enable the prescribed Rx to be exactly matched. One understands these days it is no longer the norm to under correct Rx’s for myopes as yesteryears often practice. Here the AFAR design peripheral fields will show more plus albeit by a small amount but perhaps over time as we have seen with Booster availability in small value plus options those for AFAR could be re-specified with higher extras of minus particularly as a greater understanding of the outcomes are appraised.
Frank Norville is chairman of the Norville Group.