In Contact - March 2005
State of Flux
After harping on about the need for high levels of corneal oxygen - for nigh on a quarter century - I am pleased that finally the majority of practitioners and manufacturers agree. This can be borne out by the fact that of the top four contact lens manufacturers, only one has yet to release a silicone-hydrogel lens. Three of these, namely B&L, CIBA and Johnson & Johnson, each have at least two silicone-hydrogels on the market.
For a quick and concise summary of oxygen issues and silicone hydrogels check out an excellent paper ?Corneal Oxygen Deficiency? by Fonn et al, in Eye & Contact Lens, January 2005. This edition was chock full of excellent papers.
You can also hear Des, in person, at the NZSCLP meeting in Napier this April. If you haven?t registered yet do so now at
http://www.nzoptics.co.nz/clconf/index.asp
It's looking like being a great meeting with excellent presenters, topics and workshops, all in a marvellous part of NZ.
Be there!
B&L have had Purevision spheres available since 1999 and recently launched their toric, the first manufacturer to offer this modality.
I have included a case report on initial experience with the Purevision toric in this edition of In Contact.
CIBA have also had their Night & Day lenses [in two base curves] available since ?99 and recently launched their O2 Optix lens. The launch in Auckland, at the Maritime Museum was a great success with useful presentations, excellent food and a fantastic magician to entertain. I have only used the O2 Optix lens for a short period but have been impressed with some excellent results. Only one of my trial subjects thus far disliked the lens and in fact preferred his Acuvue Advance lenses, worn for around one year.
Of course it works the other way too?
J&J have had their daily wear Acuvue Advance on the market for a year. I've had some great results but research and clinical observation have shown that these lenses can be prone to a lipid build up in around 7% of wearers. Expect about one in ten to need other options. The use of peroxide based AOSEPT & OMNICARE seems to minimise these deposits. Recent advice - to ignore the ridiculous ?No Rub? marketing on MPS solution bottles - also apparently minimises lipid deposits.
I guess that's a no-brainer eh?
In the February 6th CL Today newsletter it was reported that J&J have released a completely redesigned toric lens in the Advance material to be known as Acuvue Advance for Astigmatism.
we're looking forward to getting our mitts on this new high Dk toric.
So what of the status of the other member of the ?Top Four?, namely CooperVisionHydronBiocompatiblesOSI?
As reported, the company - correctly known as CooperVision - recently completed the purchase of OSI, for what some wags in the industry reckon was a very high premium. The possible reason?
Well some surmise that as the only company in the top four without a silicone hydrogel on the market, it may well be that they were after Ocular Science?s long awaited and rumoured silicone-hydrogel. It was hinted at by a presenter at the Hunter Valley, ICLC meeting in March 2004, almost a year ago, but I've heard nothing since.
No doubt we?ll be hearing more on this in the near future.
Deposit Management
Historically we've had protein binding to ionic hydrogels [FDA Group IV]. Switching a protein-prone patient to a non-ionic Group II material often solved the problem. Similarly, refitting a lipid-binder from a non-ionic material to an ionic material, also helped. Unfortunately most silicone-hydrogels have been bundled into the old FDA Group I category which was categorised for low water non-ionic lenses. Purevision is in the Group III, ionic, low water group.
In reality silicone-hydrogels should have their own categories [say Group V and Group VI].
My view is that they should be rated by their surface treatment [or lack thereof] as well as water content and ionicity.
As mentioned one patient complained of ?greased up?, poor vision and was much happier in Acuvue Advance whereas others who greased up significantly in Advance were much happier in 02 Optix.
So with time we will learn, through coal-face clinical experience, which lenses behave in what ways and how best to manage them with material changes.
We know there's no panacea but the more options we have, the better we can provide the excellent care our patients deserve.
Here?s hoping the researchers and powers-that-be help us characterise these properties in a sensible manner.
Lid Wipers?
As reported, the January 2005 edition of Eye & Contact Lens had many items of great interest.
The first to catch my eye was entitled ?Lid Wiper Epitheliopathy and Dry Eye Syndrome? by the legendary Don Korb and colleagues.
In a nutshell they showed that epitheliopathy of the lid wiper [? that portion of the marginal conjunctiva of the upper eyelid that wipes the ocular surface during blinking?] was responsible for dry eye symptoms - even where classic measures of dry eye were normal.
This paper adds greatly to our understanding of what must be the most reported symptom in contact lens wearers. The lid wiper, consisting of stratified squamous epithelium is located in close proximity to the meibomian glands.
Many of you may have noted comments such as ?posterior migration of the meibomian gland orifices? in reports relating to ?Toxic Tear Syndrome? [TTS] and dry eye, which one would surmise, affects the function, integrity and/or relative position of the lid wiper.
In addition other conditions such as blepharitis, CLPC, entropion, ectropion, notching and the like, would also affect lid wiper form and function.
Many people believe the incidence of dry eye and TTS is on the rise. Some say it is due to better clinical detection but antigens - such as potentially toxic and allergy inducing chemicals found in cosmetics, soaps, contact lens solutions, pollution and so on - are taking their toll on the ocular surface and adnexae.
As practically the only practitioners that look at these structures so closely we have a duty of care to timeously and adequately manage these problems before they get out of hand.
Corneal Ulcers in Two Children Wearing Paragon Corneal Refractive Therapy Lenses by Marian Macsai also attracted my attention.
I bounced it off Melbourne based Ortho-K expert Russell Lowe and he commented thus; ?I could not agree more with the authors? final conclusion. Here, we always adopt the extreme caution approach especially with children. After all, we know there are risks associated with overnight wear. The data is unclear regarding the risk of overnight wear of retainer lenses for corneal reshaping compared with CW lenses. Overall, the GP lens data stacks up well against hydrogel and even Si-H lenses worn overnight. The incidence of MK with CRT is probably small but anything greater than zero is unacceptable. The risk probably depends more on factors other than lens design or manufacturer, such as practitioner competency, practice management & organization, patient training, patient compliance with hygiene & lens care and adherence to a carefully planned aftercare protocol.?
I recall reading an article [that eludes me now] which mentioned that children have a greater corneal oxygen demand. Dwight Cavanagh and many others have published papers regarding Pseudomonas aeruginosa. Dwight?s research was also presented at the aforementioned ICLC meeting. There are many articles too, regarding Ortho-K and children.
The bottom line is: Take extra care with kids in Ortho-K!
All the papers in this edition of Eye & Contact Lens are worth a read, including the letters page.
Now that's a pretty good effort as It's rare to find a journal where you actually want to read each and every paper.
Whether you always understand them or not is another matter - especially for an intellectually-challenged, board-regarded incompetent, immigrant Jaapie with a Pommie qualification.
that's another matter gradually building momentum.
I must say I found last month?s letters rather interesting?
It seems that by far the majority of communication I have had regarding the board centres around a perception that they are tardy in replying to letters [if at all] and that when they do their undemocratic, dogmatic, elitist-idealism dominates. It also appears that they can?t actually tell people what the hell they must actually do. They seem to have jumped the gun in making the restrictive, ad hoc regulations, before the mechanisms for ?competence assessment? ?upskilling? and audits had actually been thought through or indeed worked out in a fair, sensible and practical manner. They keep changing their minds and keep moving the goalposts. It's a ludicrous situation and more fitting of a Robert Mugabe tyranny, than taking place in a supposedly democratic New Zealand.
we're all left hanging?
PVT and SLIM Reversal
As opposed to PMT and Slimming this heading relates to a great new contact lens option: PureVision Toric. [PVT].
Here?s the case report I promised.
It relates to a now presbyopic lady who, the record shows, has been wearing soft lenses for around twenty one years. The prefit spectacle refraction was recorded as;
R -1.50/-0.75x160 L -1.50/-1.00x10.
I noted that colleagues had unsuccessfully tried 1980s style EW, RGPs and in later years disposables. Colleagues had also tried Spectrum and CIBA Torisoft?s and recorded ?miss-location? as the reason for failure. A pair of NuToric 38s were finally fitted with good stability and vision.. At this stage she was already up to;
R -2.25/-1.25x170 L -2.00/-1.75x180.
I first met this pleasant, motivated lady in 1997 when I took over her contact lens care. After discussing the issues I advised her of the fact that I was refitting her into higher water lenses and re-ordered her Rx in NuToric 55. Within days of dispensing these she developed ?sore, red eyes? and slit lamp revealed bilateral SEALs. I redesigned the lenses but these mislocated and in fact the left lens did a ?one eighty? and located with the scribe mark around 12 o'clock. I also fitted some NuToric 67s with similar problems. I have previously reported on issues with the 55 and 67 materials used by the manufacturer, mostly relating to SEALs.
At this point she advised she was reverting to her tried and tested NuToric 38s. Part of her problems related to ?dry eye? with a rather low BUT.
Not one to give up easily I ordered and trialed various lenses at each aftercare but alas none worked. These included, Omniflex and BENZ G5X custom torics, Acti-, XCEL, Biomedics, Proclear and SofLens66 disposable torics - all with a combination of problems mostly relating to dryness, comfort, instability and breakages.
At each attempt I grudgingly ordered her a new pair of her trusty 38s or she reverted to her current lenses after an intensive in-office clean.
Believe me it wasn't for a lack of trying and these attempts came at considerable cost to the patient, practice and suppliers.
Thus when I returned from lecturing in South Africa in October I was very keen to put her into some PureVision toric lenses which we were evaluating.
Refraction in October 2004 was;
R -3.25/-2.00x12 L -2.00/-2.75x 176
This represented a significant increase in myopia and astigmatism compared to her Rx twenty years prior.
How much of this shift was myopic progression? How much was Soft Lens Induced Myopia [SLIM]?
The fact that this was mostly SLIM - as a result of long term hypoxia - becomes very clear when you compare prefit K readings with those just prior to refitting the Purevision torics as follows;
Prefit K R 42.75/44.37 compared to November 2004 Ks of;
R 43.62/45.75
Simple maths shows that this is around 1.00D steeper and thus largely responsible for the increase in myopia and astigmatism. The left was similarly affected.
Even I was surprised at the amount of oedema!
I usually expect around a 10% reduction in myopia when we provide the cornea with more oxygen, but as predicted by the above K changes, this one bounced back a lot more.
After just over 3 weeks in her first set of Purevision she commented enthusiastically that the lenses were more comfortable than her trusty HEMA torics.
Yippee!
After eight years of battling I can tell you that was music to my ears. Her only complaint was that her ?near vision? had got progressively worse over the past weeks. That too was positive news as it was probably due to myopia reduction and this was confirmed by over-refraction of;
R +1.00 L +0.50.
Almost what one may expect from the aforementioned K changes.
Spectacle refraction confirmed this with;
R -2.00/-1.75x10 L -1.50/-1.75x180.
I've had other cases of RGP intolerant Keratoconics who reported reduced dryness compared to their SofLens66 Torics and so far all my trials have been much improved in symptoms and comfort with pretty good stability and vision.
So if you?ve been letting things ride with your HEMA patients, there's now absolutely no excuse to leave anyone in that obsolete technology. Most patients will not only succeed and benefit but will be much better off as far as long term corneal heath is concerned. You have to at least give them a try with the benefit of healthier, happier, whiter eyes.
As one colleague put it, you need to collect Dk-yoto credits by fitting high Dk lenses to offset those you still have in HEMA!
Viva Oxygen.
For more information or any comments email Alan at incontact@optom.co.nz.