Most of us recall the Biblical passage ?In the beginning there was light?. As stated last month the universe exists because of light and everything revolves around light. Our profession is all about light and the perception thereof.
Unfortunately, like most things, light also has undesirable side effects, not least of which is ultraviolet radiation [UVR] and the temporary or permanent damage it causes.
A recent editorial in the journal Eye & Contact Lens: Science and Clinical Practice, May 2005, Volume 31, Issue 3 p9 by Jan Bergmanson makes some very valid points.
Jan?s editorial UV Overdose vs Hyperoxia raises some interesting issues.
He mentions that UVR levels can exceed safe levels nine out of tens days in some populated regions on Earth. Jan goes on to discuss the current Dk/L of silicone hydrogels and regular hydrogels as well as the fact that so far only one silicone hydrogel offers significant UV blocking.
EW vs DW is also discussed.
He asks the question as to whether UV blocking should be the primary prescribing decision of if oxygen is more important.
In an ideal world we want both.
As Jan correctly stated we already have a two week disposable, daily-wear UV blocking, high-Dk silicone hydrogel on the market.
Acuvue Advance and the forthcoming Acuvue Oasys both reportedly provide the highest UV A&B protection of any soft lenses on the market. In addition they are both lower modulus lenses than traditional si-hy lenses and include the ?123? J&J eversion indicator and visitint. Advance provides at least three times the minimum Holden-Mertz oxygen transmissibility for daily wear and the Oasys provides around six times this amount. The Advance lens almost reaches the EW minimum [87units] for EW and Oasys easily exceeds this level.
All this ?minimum oxygen? stuff is of course under constant debate, and has been for decades.
Some people want to rate lenses by Dk or Dk/L, while others want to specify oxygen performance in terms of oxygen flux, Brennan?s %Q or Hill?s EOP.
What we want, and what our patients need, are lenses whose O2 transmissibility approaches or equals no lens oxygen levels and at the same time resist dehydration, provide excellent comfort, vision and UV protection while avoiding infection and other CL complications.
If that was light relief, give me some air.
Also know as phototoxicity, light damage can occur not only from solar radiation [causing among others things, UV keratitis & solar retinitis] but also from a whole range of artificial light sources of which LASERS and operating microscopes are probably the best known. It is however worth noting that warnings included with such things as BIOs certainly suggest circumspection when it comes to ?overusing? the bright halogen light sources that are part of gonioscopy and ophthalmoscopy [Slit-lamp, direct, indirect & retinal photography.] In fact one such instruction manual suggests the following; ?The risk may also be increased if the person being examined has had any exposure with the same instrument or any other ophthalmic instrument using an intense visible light source during the previous 24 hours. This will apply particularly if the eye has been exposed to retinal photography.?
They suggest the risk may be higher in children and diseased eyes.
Bear this in mind next time you turn up your BIO ?full on? or feel like practising a technique that is not clinically indicated, on an unsuspecting patient. Limit observation time and/or illumination. Especially if you have also taken digital retinal images and may have to refer for retinal surgery or further light-based diagnostic tests or treatment within the following 24 hours.
There are useful articles on the subject in Clin Exp Optom 2005; 88: 4: 195?196.
One of two editorials; When is artificial light hazardous? is a good overview while the second asks Is artificial light at night too much of a good thing?
A review article by Vos and van Norren titled Retinal damage by optical radiation. An alternative to current, ACGIH-inspired guidelines gets into the nitty gritty. It was interesting to note the recommended exposure time of, for example, an operating microscope!
There are thousands more links on phototoxicity here.
As you may well have noticed Auckland enjoyed its warmest August on record.
Buoyed by the weather one warm full-moon day, I decided to plant our tomatoes early. Fortunately I'd spent a few winter weekends preparing the compost and veggie beds. I popped off to the local King?s Plant Barn and was fortunate to find some early tomato punnetts. While adding lettuce and other assorted veggies to my trolley I overheard two members of the Remuera blue-rinse brigade sarcastically remark that they'd ?never even think of planting tomatoes before late November?.
Normally I plant on 1st September and am lucky if I have the first few tomatoes by Christmas. I'm thus pleased to report that one hothouse-reared hybrid I purchased is already carrying around a dozen fruit and some are slowly ripening, mid September.
With this unseasonably good weather, I hear some people remark ?Bring on global warming?. I suspect though that they or their offspring may not find it that desirable.
It may also well be, by the time you read this, that we suffer the usual pre-Christmas, wet and windy weather?
Bring on Daylight Saving?
Apart from the dozens of letter and emails received over the past year regarding the APC fiasco, September?s In Contact, regarding Efron?s desperate last gasps of rigid contact lenses, resulted in unprecedented emails from all over the planet. Within minutes of the international and subscribers version going live I had my first response from a US based colleague. It simply said ?Great newsletter - I thoroughly enjoyed your rebuttal to Nate. Keep up the good work!?
They?ve kept coming for days.
These came in from the UK;
?As a practitioner lucky enough to have had a mentor that enjoyed RGP lenses I could not agree with your comments more, as a practitioner who now works for a specialist contact lens manufacturer I agree that the RGP market is not dwindling and in fact could be grown especially in the UK where we have unfortunately gone soft. It was great to read the article and gave me hope, thanks.?
Another refined British gent had this to say ?Good on ya mate!? as did another UK expat in the America?s ?Great, Mate, About Nate!!?
I am glad to see that Nuzullin Inglish and Strine have had such a rich influence on these optometric leaders.
Also from England;
?I gather Nate may be on the way back to Oz - maybe he needs an environment where they never fitted RGPs so that he can claim he was right all along!?
Indeed Nathan will be in Queensland as Research Professor, School of Optometry at the QUT.
I hear John Mountford and a few other staunch RGP-rednecks will have a welcoming party waiting for him when he lands.
Nathan has also challenged me to a debate on the RGP issue at a future Australasian Contact Lens Conference.
I welcome it.
A compatriot had this to say;
Sad how many academics feel they have to slate what they can?t teach, in that way making their predictions come true. Industry, too, has an interest in this prediction coming true. Ethics, anyone?
A US based expat South African commented thus;
??thanks for your article which I really enjoyed. My 12 year old is in ortho K rgp lenses, and bifocal quality of rgp far outweigh the vision of softs thus far. I am enjoying working with sclerals that allow good vision without transplantation in Keratoconics. In 1979 as soft were making headway my myopic ?spear chucking? Prof said firm lenses won?t be around in a few years and as such did not teach us anything about them. Personally I like to have as many options to address the visual needs of all my patients.
Other colleagues around the planet had similar views and like me acknowledged that on the whole Nathan produces great resources and is an excellent presenter. We do however note his occasional exaggeration.
?Enjoyed your article - I agree with you and always prefer to fit the youngsters with RGPs if they?re going to be regular wearers. Happy to let them have soft if It's for occasional wear only...Must admit to enjoying Nate?s lectures, but usually take his thoughts and predictions with a lump of salt...?
From Israel I received the following comment;
?I very much enjoyed your article on RGPs. I teach Contact Lens Practice to Optometry Undergraduates. I (teach) the art of hard contact lens practice and encourage our students to fit them in our open clinics. I am as yourself, determined to continue to ?preach? the tremendous satisfaction for the practitioner who understands the intricacies of hard lens fitting and your article gave me encouragement.?
There were many more and I enjoyed this one from Scotland.
?After the English you Kiwis don't half go on about winning stuff, I am not too bothered about the Lions as there wasn't a great Scottish input to the squad. It's a shame you guys aren?t daft about curling and speedway the sport us Scots are doing not bad in at the moment.
I am relieved to read your response to Efron article. I only qualified last July but now spent a fair bit of my time fitting ortho-k lenses and also keratoconics. (Efron?s) article made me feel I was being condemned by the authorities in our profession.?
I pointed out to the Scot he should be glad the ABs took out the Boks or else he would have had to put up with a crowing Jaapie.
One further point: Last month I quoted the research paper that noted 11% of new fits were RGPs. In fact that was the international incidence and in fact both NZ and Oz rated a higher 16% - among the top five RGP prescribers after Holland, Japan and Denmark.
Again RGPs are hardly in decline or virtually obsolete. In the Netherlands 23% of new fits were RGPs.
Nathan may well find himself between a rock and a hard place come 2010?
For more information or any comments email Alan at email@example.com.