In Contact - July 2007

A Meta-Analytical Crisis?

It seems that meta analysis and evidence based medicine is increasingly becoming the ?in thing?.
These days numerous papers review past studies, collate the results, analyse them statistically and come up with trends and conclusions.
We see it in many aspects of health care and vision research, drug and vitamin studies, AMD and now this one; Risk of Corneal Inflammatory Events with Silicone Hydrogel and Low Dk Hydrogel Extended Contact Lens Wear: A Meta-Analysis by Szczotka-Flynn & Diaz in Optometry & Vision Science: 84(4):247-256, April 2007.
The most startling conclusion?
They found a two-fold increased risk of corneal inflammatory events in 30N EW of silicone hydrogel lenses when compared to 7N EW of low Dk conventional hydrogels. Of course there are caveats and the paper raises interesting questions about oxygen, EW and number of nights, lens type, design, material, modality and of course the effect of solutions and interactions. Check it out.
The rest of this edition is also worth a read as It's a ?special? on contact lenses and suboptimal environments.
Another paper covers ?corneal inflammatory events? [CIEs], resulting from solution issues: Solution Toxicity in Soft Contact Lens Daily Wear Is Associated With Corneal Inflammation by Carnt et al concludes that daily wearers should be seen soon after lens insertion and undergo a slit lamp exam with NaFl. Solution/lens combos should be modified depending on the corneal reaction.
Corneal staining indicates a potential for further complications and thus careful attention needs to be given to the correct lens/solution Rx. I will not repeat all this as It's been well covered in previous columns as well as at the recent CCLS conference, in journals and on the silicone hydrogels website.
There is one further comment on staining though: don't ignore conjunctival staining, whether tarsal, bulbar or palpebral. Look too for ?inclusions? such as make-up particles and mucous type. Is it present at a canthus or bilaterally at the canthi?
Such subtle signs may aid differential diagnosis.
I've also commented on CLPC and allergies with si-hy lenses and we continue to see increasing ?chatter? in this regard via online email ?lists?, forums and published articles. With the US [and others] increasingly prescribing si-hy lenses reports will increase. If practitioners don't pay enough attention to signs of inflammatory lid conditions and allergic individuals we will see a spike.
In my experience It's these cases that are most likely to develop full blown inflammatory lid conditions: Whether at the lid margin, ocular surface or tarsal conjunctiva.
GPC in si-hy wearers has been reported with all currently available lens types. It's not all modulus related and as stated I believe there are certain individuals that seem to show ?silicone allergy?. Others share this view. Some don't.
We see it too in RGPs where some individuals seem to react to silicone acrylates [and other silicone containing polymers like FSAs]. Sometimes It's just a question of how much silicone the lens contains as changing to a higher Dk [more silicone] can trigger the reaction while a different polymer may be tolerable. Although very rare I have seen a few RGP related GPC cases. These have typically occurred in noncompliant wearers whose lenses are almost opaque from protein. Some have not had a check up for many years; as long as five, seven or ten years in some cases.
These usually resolve relatively quickly.
After an in office clean and polish the papillary reaction is often dramatically better by the time new RGPs are dispensed, a week or two later.
In the case of silicone hydrogels I usually recommend a switch to daily disposables and avoidance of EW. If dailies or RGPs are not an option then ideally a non-ionic or zwitterionic high water lens with peroxide disinfection is my next choice.

Primo Papers

The CLAO journal Eye & Contact Lens: Science and Clinical Practice and CL Spectrum also continue to deliver top class, relevant papers as do Optometric Management and Ophthalmic and Physiological Optics
A recent Spectrum paper; Treating Allergy in Contact Lens Patients by John L Schachet, a well regarded OD, is certainly worth a read.
Of course we don't have to look any further than our own backyard to find what is in my view one of the very best eye care journals. Clinical and Experimental Optometry delivers a wide variety of eye care issues. A recent one on compliance, The effect of a compliance enhancement strategy (self-review) on the level of lens care compliance and contamination of contact lenses and lens care accessories by Yung et al satisfies the criteria for quality even though it tells us something we already know and I quote ?All subjects showed some degree of non-compliance and the spectrum of non-compliance was wide?
Read it as it may give you a deeper insight into compliance issues and strategies to improve this critical aspect of long term contact lens care, management and safety. Simply log in via the NZAO [Click ?members? for journal access], or via the OAA site.
One aspect of compliance regards contact lens cases. Much research has been done and confirms that cases are often contaminated.
By all sorts of things!
there's a massive variation in recommendations regarding case care. Does one ?air dry? it as some people tell us? Air drying a lens case, open on the basin in shared accommodation can mean that at the end of the day it contains all sorts of ?stuff? from one?s flatmates including shaving stubble, hair, creams, spit, toothpaste and so on. I've actually seen such cases on a number of occasions?.
Some suggest storing it to dry, open in a ?protected area?. I doubt those making such recommendations are aware of the levels of mould and airborne fungal spores likely to be found in your average million-dollar damp, leaky Auckland home? Others say replace the solution and store it closed with fresh solution. Yea right! Our industry driven, ?no rub? non-compliant?s are really keen to double their spend on solutions!
The silver ion CL case that ships with Aquify in NZ may help?
Wanna know the best option to avoid this long standing Pandora?s Box of potential pathogens?
Fit Dailies.
I've been saying that for a few years eh?
Some thought I was a bit radical on this issue and that the ?new EW? would reign supreme, however many things continue to show that dailies are best. MK is lowest with dailies. Solution incompatibilities don't exist with dailies. Dailies are the modality of choice in CLPC/GPC. Comfort is often better. Convenience is also pretty good.
Need I say more, except to the manufacturers?
Bring on high Dk dailies.
It's time

Feeling Bullish?

It was also about time that the Blue Bulls won the Super 14 and they did!
You can imagine that this born and bred former Pretorian was one of the happier people in NZ at 3am, Sunday 20th May.
What a game. What an ending. A fairytale.
What the Sharks did to the Crusaders with their ?after the bell conversion? a few weeks ago, the Bulls likewise did to Pretty Percy and his merry men.
Of course I got all sorts of emails the next day. Some said it was the [Kiwi] refs fault. Others said it wasn't great rugby, riddled with errors. From where I sat I could see no more errors than the Cocky Cantabrians made in their loss to the Bulls?
It was a final after all.
Less biased international sports writers said it was the ?best final in a decade?. What?s even better is when legendary Kiwi scribe ?Inky? also says it was ?right?.
I must also thank the ?brothers beyond the Bombay?s? for softening up those mainlanders and easing the way for a Bulls home semi.
I saw staunch Crusaders backs fumble and drop the ball in their semi and the Bulls forwards destroyed them in the last ten. The Blues coped better in their semi against the Sharks.
The Sharks had won the final at seventy nine minutes but like so many teams in the past forgot that It's a game of two halves and sometimes it is an eighty three minute game.
It ain't over till It's over.
The outcome bears veridical testimony to the great efforts of the highveld Bulls of Loftus.
I played a few rugby games at Loftus in my youth, although in those days it was a reasonable facsimile for concrete that would have seen Habana skinless after his great match winning swallow dive. These days the grass is a lot greener and softer.
I look forward to the Tri Nations and RWC with increasing vigour as it seems some of the ?reconditioned? [and rehabilitated?] ABs may not be as invincible as some thought?
Bring it on!
Last month I reported that F1 rookie Hamilton was doing well, was tied-second and broken all rookie records for podium finishes by his third race. As of the Spanish Grand Prix he was the first rookie ever to lead the world championship standings in his first year, never mind by the fourth race.
By the time you read this the wonderfully quaint Monaco Grand Prix will have been run.
It's always a race of surprises.
Will Hamilton win his first Grand Prix or will he become another victim of the oh-so-close ARMCO?

 

For more information or any comments email Alan at incontact@optom.co.nz.