In Contact - February 2005
Greetings!
I hope 2005 is good to you.
It seems my prediction of Summer starting plus or minus two days of Xmas was pretty well spot on. We did get two days of summer a day or two after Xmas. Then it went back to the miserable weather we've had since June. As I write this, mid January - with most people now back at work - we're having some of those marvellous days that Auckland can deliver.
When it feels like it.
Unfortunately I think my other prediction of an optometric manpower shortage in NZ and our profession being screwed by the Wellington Bureaucrats [WBs as opposed to WMDs] is already starting to happen. Reports of UK qualified optometrists who had shown an interest in working in NZ are simply saying ?Stuff it. Too much hassle?.
Some of you may have noticed that I got my ?botty spanked? in a personal attack and reprimand via a letter to the editor from the ?Chairman of the Board? in the December edition of NZ Optics. This month you can read two letters in response to that elsewhere in this edition. Thus I won?t waste valuable column space in this edition responding, nor did I feel like wasting valuable family time over the holidays even thinking about it.
I will however, in future, be discussing issues raised by board members in recent letters. As we get further down the track on resolving this over-the-top doctrine and petty posturing, there will be much to say and do.
It also seems that a tactic of these critical letter writers is to submit them so close to deadline that I don't even have a chance to exercise my right to reply!
Of course in the bigger scheme of things, there are much more important issues, especially in comparison to those devastated by the Tsunami.
It was interesting to note that one of the biggest earthquakes in the past few decades occurred between Invercargill and Tasmania two days before the Indonesian quake, on 24th December. According to some sources and maps, these were quakes at opposite ends of the same fault line/tectonic plate. As most of us know, we residents of the Shaky Isles could well suffer a similar fate, as it really is just a matter of time until we get hit with a similar natural disaster.
Hubba Hubba
One can almost smell the burning rubber as we get ready for the official launch of two new silicone-hydrogel lenses on the NZ market during February. I suspect there will be others to follow later in 2005.
B&L?s PureVision Toric should prove a boon to those oxygen-starved corneas in wearers of conventional torics and even modern disposable torics, as these too, are often shy of the minimum Dk/L for daily wear. I hope to present a rather interesting case report in March, which shows just how much oedema and soft lens induced myopia [SLIM] can be present in traditional soft toric wearers, even in relatively low powers.
CIBA?s O2 Optix will also be launched in February, apparently as a monthly disposable daily wear lens. As we know, contrary to instruction, many wearers tend to sleep in their low Dk lenses so a lens such as O2 Optix, with a 138 Dk/L- approved in the US for up to 6N EW - will certainly provide a safety net for the occasional ?flexi-wearer?.
We continue to have significant debate surrounding oxygen claims and ?minimum safe levels? to avoid oedema ? for daily wear and extended wear. More recently we have much higher Dk levels being quoted to ?avoid limbal hyperaemia?. As you know I have always pushed for more oxygen and have come under flak for at least two decades, from some of my colleagues. I make every effort to be damn sure of the facts.
CIBA recently had to back down from unsubstantiated claims regarding ?critical minimums? as far as oedema and oxygen are concerned.
So the ?oxygen wars? I've previously reported on in-depth, continue. This time it was CIBA?s turn to get a rap on the knuckles.
All I can say is that the more developments that occur in silicone-hydrogels the better. I reckon we can expect more comfortable lenses with lower modulus, better deposit-resistant surfaces and enhanced aberration controlled optics.
By the end of February, most practitioners in NZ & Oz will have access to five different silicone hydrogels, from three manufacturers. I continue to see excellent results with Purevision and Night & Day over the past 5 years, in both DW and EW. One year down the track, we're seeing some very happy patients in Acuvue Advance on a 2-week, DW modality.
Silicones provide many advantages. Whiter eyes say a lot. Better dry eye management is another benefit. Apart from rare infections, lipid deposits and undesired topographic changes are the main problems.
So no matter the debates and law suits, the bottom line is you cannot let too much oxygen through a contact lens. The closer we get to ?no lens? levels of oxygen the better, so long as the lenses meet all the other criteria of good comfort, optics, and biocompatibility.
There?ll be no hubba hubba if you don't fit silicone rubber!
Best RGPs?
I often get asked for advice on what material to use in RGP fitting. As in the above discussion, oxygen is King. Fortunately RGP lenses fitted for daily wear are a lot more forgiving as the blink-induced tear pump provides around 30-50% of the cornea?s oxygen requirements. that's the reason no Dk PMMA worked in the first place. As with soft lenses, in RGPs we have the same needs for deposit resistance, quality optics and comfort as well as an even stronger need for material stability and longevity.
So in a nutshell and where all things are equal, I would fit Boston?s wonderful ?100Dk? XO material 90% of the time. I can also tell you that I am now seeing many patients that have custom made lenses in Boston XO fitted in 1997 and 1998 that are still going strong. This is well in excess of what most would consider an adequate lens life. For example some practitioners in the UK advise annual replacement and many the World-over would be happy with two or three years. Of course like any material ? and I must say it often seems patient specific ? lenses can and do warp and become distorted. Anecdotally this seems to occur in patients with tight upper lids and significantly toric corneas. I figure if similar tight lids can alter corneal topography, they could also warp a lens? Of course some patients scratch the hell out of their lenses, often aggravated by poor case design.
There are however patients who react to certain polymers, especially higher Dk materials. In some cases we see allergic reactions, poor wetting and ?deposits?. In theses cases I would tend to refit Paragon?s excellent Fluoroperm 30, which has proven itself as one of the most robust, best-wetting lenses, in situ, with great stability and longevity.
XL40 aka Paraperm 02 is probably the ?best? RGP lens ever developed, historically speaking. After around two decades XL40 is however getting a bit ?long in the tooth? as its Dk in the low teens is not really adequate for long term wear. I reckon I can successfully refit 90% of my patients from Fuoroperm 30 and XL40 directly into Boston XO offering around three to six times more oxygen, respectively.
Apart from an apparent blip in material ?compatibility? in 1998, Paragon?s HDS 50 is also a lens I fit as a mid Dk lens - particularly in cases of patient intolerance or stability with XO or previous attempts in refitting higher Dk lenses. In a previous column I mentioned - with my usual disclaimer that ?time will tell? - a new material, Optimum Extra. It seemed promising. Some of us in NZ have unfortunately had some wetting problems, patient intolerance, a few cases of lens instability and even ?spontaneous breakage?.
The ultra high Dk Menicon Z material with its 163Dk continues to be popular but I tend to only use this material for EW RGP cases as its treated surface prevents modification, polishing or repowering which I still regard as essential for daily wearers. In saying that however, one of our staff wearing a Menicon Z for EW over the past month reported a spontaneous breakage of her right lens, just as we go to print.
So if I only had access to one RGP material, what would I choose?
I'd have to say Boston XO.
If Asian cooking interests you try Lee Kum Kee?s renowned XO sauce ? but wash your hands after using it and before inserting contact lenses. My favourite chef in the world, Neil Perry, has opened another world class restaurant in Sydney, aptly named XO and a tribute to XO sauce.
Optics Anyone?
I?ll never forget our optics lecturer in first year optometry performing Huygens? Construction on the board with board compass and chalk.
How things have changed.
In recognition of his work, the Saturn and Titan probe was named Huygens.
After seven years it finally touched down on Titan, mid-January ?05 and has started relaying these images - the first ever glimpse of Titan by an earthling.
Amazing stuff.
I wonder which brave practitioners will get into this market?
Or we could send them down to the local Tattoo shop and have a pair of cosmetic contact lenses thrown in!
For more information or any comments email Alan at incontact@optom.co.nz.