Letter to the editor

Dear Editor

Within the October issue of Dispensing Optics, one noted a disappointing revisit to poking that blue hornet’s nest: ‘Blue light guidance stands’. I would have thought it perhaps more prudent to have let this sleeping dog’s breakfast of historic mishmash blue to fade into the dust of time.

Mind you, it was helpful to be reminded all this was seven years over the hill. Differing interpretations can be attributed to this saga depending on how diplomatic you wish to appear. In essence, two major dispensing groups appeared to be vying between each other as to whom might claim the manufacturer’s prize for the highest level of blue reflex anti-reflective (AR) coated lenses sold and, in their enthusiasm, things did get a little out of hand.

Now I don’t recall anyone at the time detailing the actual absorption/transmission characteristics of the lenses involved. The lenses that caused this rumpus were just multicoated anti-reflection coatings but with a blue reflex rather than the more regular green reflex.

Figure 1 © Ellivron

Figure 1 compares the transmittance curves of an emerald reflex to a blue reflex AR coated lens. The key to all of this is the resulting blue percentage data figure: MARE lens just attenuating seven per cent of blue light whilst blue (MARB) doubling this figure to 15 per cent. Norville, at that time, had a KBLU coating which was even more effective – coming in at closer to 25 per cent blue absorption (Figure 2).

Figure 2 © Ellivron

Such lenses delivered small incremental improvements as blue light absorption filters. All the while, experimental work was in hand on more effective blue blocker designs to combat harsh LED blue light (455nm) and other spectral areas. I can recall reading a professor’s view that single nanometre steps matter.

Perhaps we should look back and remind ourselves of the journey travelled over the last 70 years to reach today’s point in time?

Early CR39 lenses had a UV absorption of sub 300nm. USA development work with dye materials brought this up to 400nm – particularly desirable for sun lenses. Vast numbers of CR39 Rxs were post treated by this laboratory process even to this day. In recent years, clear UV400 1.50 resins have been made available as factory-produced stock lenses – as did newer and higher index materials – naturally absorbing higher values of UV.

Recently, Japanese material manufacturer (MITSUI) has produced a UV420 material – although UV410 might be a more correct description. However, it’s significant that over those 70 years, the UV cut-off point for ophthalmic lenses has moved along from 300nm to 410nm. So is it now time to bring to a halt this steady journey along the spectrum of UV and blue cut-off – or do we continue to press on higher? Should we recognise LED lighting, with its sharp output peak at 455nm, as an issue that should be addressed next? Think of all those who work under LED lighting, those on permanent night shifts whom see nothing else? Might we ask ourselves why all those aged ‘rockers’ seemingly constantly wear heavily tinted lenses after all those years under harsh photo-flood lighting have taken a visual toll?

Perhaps, with the likely exception of the late Dr OTT, an advocate of full transmission lens materials, this UV-blocking upward trend has been heralded as a beneficial move by the worldwide ophthalmic community. It’s possible we shall never know why this fresh Cochrane summary suddenly appeared. Someone must have authorised it. One suspects very few will read each and every one of its 96 pages – perhaps just managing to get to page two and its conclusion of just four lines: “There is need for future research to provide evidence”, which is a telling conclusion to this rather sad ophthalmic chapter.

Reviewing page by page there would appear to be considerable confusion amongst supervising participants as to what lenses they were actually using. Crizal Prevencia was a frequent chosen blue light filtering lens (which it is) but then further reference to BBL’s one assumes blue-blocking lenses, which they probably are not. Whilst occasionally the report references other familiar trade names, this is often not so other than UV cut-off. With no transmission graphs published that would have given useful clues as to individual lens performances, at least a partial summary offered on pages 91. Halfway in, I came across page 45, which brought me up with a jolt: a blue light filtering spectacle lens with orange lenses reported to eliminate all light below 540nm. Sounds like Norville’s old PLS 540 tint (Figure 3).

Figure 3 © Ellivron

Now I just cannot understand how anyone could possibly hope for any useful conclusions that would withstand withering critique when there is such a glaring difference in the transmission characteristics of this blue blocker (Figure 3) against light blue filter (Figure 1). Study those transmission charts and then wonder that this latest exercise is a long way from where all this started. This is no more than an apparent attempt to compare orange apples to blue pears.

During the first Covid lockdown, a very significant event was the almost total cessation of ophthalmic activity (hospital eye departments excepted). Our regular clock beat of ophthalmic demand just fell silent. The flow of optical consumers through optical practice doors temporarily ceased. However, some of those more knowledgeable keyboarders realised online ophthalmic sales were still accessible, resulting in a flow of online orders turning into a flood as the public went into a frenzy of self-selection spectacles. Why do we know this? Because we had kept key skeleton services in place across all our locations to supply and maintain local eye hospital services. Then along came a request to glaze 1,000 spectacles of daily online demand. We could only manage 50 per cent of that number and we soon ran out of lenses – but here is the fascinating point: nearly half of that demand self-selected by the public themselves were for blue reflex MAR-coated lenses. Even our long-standing policy of holding excessive stocks (no lenses – no production – no sales) was blown away in just a couple of days. It was a total revelation.

There is another significant change factor, which has arrived over this seven-year period. That is input from Professor Shelby Temple with design and provision of his MP-Eye instrumentation, which I understand indicates a grading of individual eyes with their natural ability to cope with sun and blue light transmissions and absorptions. A process, whose output data could add yet more fascinating detail to those blue deliberations ‘who what and where’ charts of those benefitting from blue filtering lenses.

Prescribers faced with users who found harsh daylight and artificial lighting tiresome could well have turned to Transitions Extra-Active whose graph (Figure 4) shows it attenuating 15 per cent across blue light whilst absorbing 100 per cent below 410 UV. Nobody could categorically claim wearing such a lens for 50 years would bring wearer benefits, but perhaps just the opposite – not wearing such a UV blocker could predict earlier cataracts.

Figure 4 © Ellivron

Finally, with all this blue technical detail in my mind, I walked into a High Street practice and immediately noticed all the ladies present were wearing blue AR reflex lenses. Remarking on their up-to-date blue light attenuating lens coatings, they all looked at each other whilst their spokesperson said, “Well, we just liked the lens colour, which also saves time applying blue eye shadow every morning“.

By way of conclusion, I consider that ABDO should take our sector lead on blue filtering lenses and rather than just whip-cracking, encourage some collective action by members to contribute to these blue lens topics. Perhaps by way of a patient feedback technical diary, which members could record interesting user comments on, that collectively might give a clue to causes and relief of visual stresses and strains, wearer routines and devising solutions. I also believe a serious return to studying transmission/absorption charts wouldn’t go a miss. It seems to have a dropped out of significance; even some large manufacturers do not provide them when actually they have never been easier to produce. It’s all in the charts.

We all understand our human visual cortex and processing system is highly complex and still little understood. There is a lots still to learn, and I firmly believe everyone has a right to contribute thoughts to that process and not to be discouraged by elites. Our country is desperately in need of innovative thinking – something that should be encouraged across all walks of life at every level.

I leave readers with this conundrum:

Figure 5 © Ellivron

Figure 5 shows the most popular prescribed filter tint of the 20th century. It was blue.

Frank Noville OBE

Max Halford, ABDO clinical lead, replies:
ABDO is committed to supporting members to continue deliver evidence-based practice. The field of blue light, and research around this subject, is certainly one that ABDO’s Research and Clinical Committee will be following.

Email your letters to the editor of Dispensing Optics, Nicky Collinson, ncollinson@abdo.org.uk

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