In Contact - March 2006
Si-Hy: H2O2 vs MPS
Ever since we embarked on the silicone hydrogel journey in late ?98 it became apparent that the Holy Grail of trouble-free, hyper-Dk soft contact lenses had not quite been reached. It became apparent that there were those individuals - particularly atopes - that seemed to react adversely.
Typically we saw inflammatory reactions, particularly in those with Meibomian Gland Dysfunction, blepharitis and prior history of CLPC.
Hardly a day goes by that I don't receive a newsletter or email from a colleague, patient or online optometric chat group, that doesn?t detail some or other issue pertaining to silicone hydrogels and the increasingly apparent issues regarding CLPU, CLPC, staining, SEALs, comfort or vision issues. Switching from multi-chemical containing Multi Purpose Solutions [MPS] to peroxide based AOSEPT solves many of these problems. Lower modulus materials may also help.
Sometime in the recent past someone at AMO decided that adding HPMC [hydroxypropyl methylcellulose] to the neutralising pill in their Omnicare peroxide system - so as to place HPMC as a lubricant in solution ? was a good idea.
It hasn't been for some of my silicone hydrogel users who suddenly lost tolerance and complained of irritated eyes and ?greasy? vision. A switch to AOSEPT solved the problem.
One of the reasons I've advocated peroxide based disinfection - over the past two decades - is that at the end of the disinfection cycle one is ideally left with plain old unpreserved saline - after the catalysation of H2O2 into H2O and 02.
If you?re allergic to either you?re probably dead?
Additives don't necessarily enhance efficacy.
I was thus not overjoyed when CIBA added a surfactant to AOSEPT Plus. Now I see problems with former asymptomatic patients when they start using HPMC containing Omnicare [Ultracare to those in other markets].
As far as I'm concerned the less additives, lubricants, surfactants, buffers, disinfectants and preservatives in solutions the better.
It seems however that the manufacturers keep adding more and in my experience reactions and interactions - especially with silicone hydrogels - keep getting worse.
Just one reason that I continue to advocate daily disposables as the first choice in soft lenses?
There are of course a whole bunch of new solutions out there that may be ?better? but which we can?t access!
It seems Medsafe are dragging the chain and clipping the ticket?
Thus we have a situation where TGA [& FDA & CE] approved solutions are now available in Aus while we in NZ don't yet have them. In some cases, like Systane Eye Drops, they?ve been on the market for eighteen months or more, across the ditch. Whatever happened to Trans Tasman Mutual Recognition?
What?s going on?
More evidence of bureaucracy gone wrong?
Surely Kiwi corneas are not so soft they need special testing to see if they can withstand an approved lubricating drop or solution?
These CL management issues are not limited to CL solutions and silicone hydrogels. Lately I've had a few cases of reduced tolerance or allergic type reactions ? in formerly happy wearers of Focus Dailies - since the ?enhancements? of AquaRelease [PVA] and Visitint.
Is there a connection?
Email me if you?ve had similar cases?
Space restraints this month don't allow elaboration on these issues but I'd be interested in feedback from colleagues who?ve noted similar [or other] issues with CLs, solutions or silicone hydrogels
More on these interesting clinical issues in future columns and presentations over the next few months.
How?s yer Pixels Baby?
As a near baby boomer and fast starting to notice the degenerative pre-death experience of presbyopia, I am more acutely aware than ever before of this frustrating phenomenon. Fortunately my mild form fruste cones have provided enough ?beneficial? aberrations to partially delay or stave off this inevitable degradation of near acuity.
we've all heard of ?aberration control?. The hype had led us to believe that wavefront guided refractive surgery and early ?aberration? controlled spectacles and contact lenses would provide ?Eagle Vision? or hyper acuity.
In practise we've seen that in fact all these refractive tweaks and refinements have achieved is ?better quality? 20/20+ vision: Rather than the 20/10 [6/3] acuity we've been ?promised?. Will we get 20/10 vision by 2010?
We?ll see.
If you?ll excuse the pun.
At the same time, ?adaptive optics? have achieved some amazing optical feats ? as reported in some of my columns and featured on Hubble, JPL and NASA links in my annual ?Best of the Web? editions.
?Deformable mirrors? and other ?tweaks? have led to some amazing images - not only from space-based telescopes ? but from terrestrial ones too.
Until recently no one had been able to come up with adaptive optics that could be applied to spectacles, contact lenses or indeed an intraocular lens.
I mean how geeky would one look?
Wearing spectacles consisting of hundreds or thousands of deformable, motorised lenses or mirrors - with a head mounted aberrometer - to constantly readjust each of the discreet optical elements that make up an array of adaptive optical systems?
It seems a number of people are working in this field. Here?s a text on the subject. Others have conceptualised a spectacle lens based system, with adaptive optics. This patented technology will apparently initially be manufactured to correct presbyopia and the dynamically variable near-work visual range that single vision readers cannot correct. Presbyopia is arguably the one visual problem that will afflict us all ? irrespective of ametropia, creed or colour. It's thus potentially the largest optical market, currently being fuelled by maturing baby boomers.
PixelOptics is a trademarked technology that will apparently use dynamic focussing ?electro-active? optics. Ophthalmologist and Inventor Ron Blum is the man behind this amazing concept. Take a look at this article in Wired News for more info and some other good links.
Of course others have achieved ways to measure aberrations and fabricate aberration reducing spectacle lenses; already available, in limited markets. One such system I've previously presented is Ophthonix & their !∙Zon spectacle lens.
To my mind a spec lens is not ideally suited to aberration control as wavefront optimised optics are point-to-point specific. As we dynamically look through different parts of a spec lens it seems to me the benefits will not amount to much ? unless we create ophthalmoparesis, so that a patient could only look through the optical centre of the lens!
Rotationally stable contact lenses are thus better suited. SynergEyes are banking on this with their proposed SynergEyes W or wavefront optimised lens.
Of course LASIK and other LASER refractive surgeries utilising aberrometry and customised wavefront-guided ablations are even better suited as are intra ocular lenses.
As I've pointed out the optical results of wavefront guided ablations - although providing better results than in the past - are still a way off 6/1.5 or indeed 6/3 vision.
Of course It's all pretty damn amazing from a technological point of view and a whole lot better than the first spectacles made of quartz rock/glass lenses a few centuries ago!
Bad Ads?
On the subject of LASIK I'm tiring of ?negative? advertising - in NZ as well as overseas - that slag-off ?the nasty hassle of contact lenses? or offer prospects an opportunity to ?get rid of those thick, ugly glasses?.
How would the LASER surgeons like it if contact lens practitioners embarked on a reactive campaign that went along the lines of ?Why risk permanent sight loss from Laser refractive surgery? when research shows that the risk of sight threatening episodes are ?almost zero? with RGPs & daily disposable contact lenses? Even 30 Day ?sleep in lenses? are apparently ?safer? than LASER!
I guess we?ll have to speak to CL manufacturers - that don't have a LASER refractive division - about a viral counter-campaign?
As a well known ophthalmologist has been heard to comment, on LASIK, while lecturing at a Contact Lens meeting, ?It's the Devils work?
Of course I've heard him say similar things about Contact Lenses at an Ophthalmology meeting?
It's all relative eh?
For more information or any comments email Alan at incontact@optom.co.nz.