In Contact - November 2008

The Dark Ages

Sometimes I wonder about the prescribing decisions made by some practitioners when refitting an asymptomatic contact lens wearer. I also struggle to understand the apparent disconnect between supposedly intelligent people with top academic results and what appears to be poor clinical decision making. Undoubtedly optometric student selection has become too academically biased and the old ?hands on? practical approach has been diluted. The shift away from contact lens practise in favour of pathology and therapeutics also plays a role.
A case in point regards a patient I refitted into PureVision in 1999, shortly after its release. I made this decision as her corneas were showing signs of corneal fatigue with distorted, zonal retinoscopy reflexes as a result of chronic hypoxia from high minus, low-Dk generic disposable wear and a prior history of long hours of conventional lenses. Two years later she visited a local optical chain in order to obtain some low cost spectacles. Although asymptomatic and reportedly happy with her PureVision lenses she was refitted into a much lower Dk, Acuvue 2, for no good reason it would seem. For the past seven years she has opted to buy more of these on the Internet. Apparently the lenses were R -8.50 and L -9.00 but she didn't know the base curve. [I had fitted PureVision 8.6/14/-8.50 OU in ?99].
Her left acuity was down around 6/24 and she needed around a -2.25D over-correction. The right eye was ?okay? in terms of vision but both eyes showed significant neovascularisation. Significant oedema from chronic hypoxia was confirmed by over 1D steeping in her K readings and as much as 2D steeper in one meridian of her left eye, which correlated closely with her induced myopic shift.
Refraction confirmed she had indeed shown a significant myopic jump in both eyes from the original visit with me in 1999. I suspected she had her lenses swapped yet when I analysed them on the vertometer she had -9.00D in the Left but the Right was measuring more like -10.00D than -8.50D. This explained why she still had good vision in the right with her CL even though she was showing increased myopia in the refraction. The worn lens powers did not match what she told me she thought she had. It shows that we still do need to sometimes measure soft lens powers on the vertometer when things do not correlate.
Oh the joys of Internet lens sales!
She also indicated she was not happy with the ?cheap? spectacles and that they had been ?useless?. I refitted her into an Acuvue Oasys, Right 8.4/14.0/-9.00D and Left -10.00D with a targeted under-correction of 0.50D. She still however obtained improved overall VA compared to the old AV2s and even as we completed the exam and ancillary tests her eyes became less red. I explained that ideally over the next few days her distance vision would improve as her corneas de-swelled and as her soft lens induced myopia [SLIM] returned to a more ?natural? level.
I also explain to these patients - often near presbyopia due to the fact they are twenty or thirty year lens veterans - that should their near vision deteriorate after a few days, then this is indeed good news and that they should then move their aftercare visit to an earlier date.
Now why the suspected disconnect?
Well we've known about the issues of hypoxia, Dk and SLIM for decades and any optometric course worth its salt should be teaching this stuff. It's also well covered in columns like mine. The siliconehydrogels website also covers it as do many decent text books, eye sites, conferences, blogs and discussion groups.
The mind boggles as to why one would figuratively downgrade from a five series Beemer to a Morris Minor? From around 100 Dk to around 30 Dk? Of course with the high minus the average or profile Dk/L becomes a bit marginal in the AV2, hence the problems as described.
At any rate we have sorted the problems. It's just a pity that between a bad decision at a chain store and a limitless supply of lenses from an obviously uncontrolled website she was able to add insult to injury and (unknowingly?) kept abusing her corneas for a good seven years?
It's good to see that in the UK online lens sellers are being fined for supplying lenses unlawfully and hopefully in time the cowboys that do this will learn the same lessons as the financial cowboys who have brought the world economy crashing down.
I spoke to the patient concerned as we went to press and she told me that her eyes were much better; ?fantastic? in fact and that the clarity was much better. As predicted her acuity had improved over the following few days. She monitored this by checking out Teletext on her TV every evening. She also remarked how much better her eyes feel at the end of the day; ?refreshed? as she described it. She continued with the OptiFree MPS she?d been using with her AV2s.
Of course there are cases ? particularly allergy problems - where we may have to reduce Dk in order to fit dailies. I featured such a case in May 2007. For low myopes Dk/L is rarely an issue. In high prescriptions one should also never discount RGPs as an excellent solution. Of course we will soon have si-hy one day lenses, so for all but the people who show ?allergy? to si-hy lenses or cannot wear regular high Dk disposables or RGPs, these problems are now solved - apart from a few extremes of the bell curve.

 

Great Minds?

You know what they say: It's either a case of great minds think alike or fools never differ.
Over the years I've noted that the CL Today newsletter and my In Contact often select the same abstract or recently published paper to highlight. It's not as if the CL Today editor and I necessarily share the same particular interest in all aspects of contact lenses as this has now happened with the three different editors, namely Joe Barr, Carla Mack and now the new incumbent Jason Nichols.
Last month as I was sending my latest missive off to the publishers, I received the September 21st edition of CL Today and noted they had featured the identical paper on Eye Blink frequency as I did in my October edition of In Contact. This month I had planned to discuss the issue of GPC [or CLPC] and its resurgence since the advent of silicone hydrogel lenses. We almost had it licked over the past decade or two since the advent of frequent replacement, disposable lenses.
I would go so far as to suggest that we define a specific version as Silicone Hydrogel Papillary Conjunctivitis [SHPC] or SHITI [Silicone Hydrogel Induced Tarsal Inflammation].
One of the papers I had intended to include was Deposition of lipid, protein, and secretory phospholipase A2 on hydrophilic contact lenses. CL Today also featured it in the October 5th edition so you can read the abstract and discussion there.
The bottom line is that I have certainly noted an increase in SHPC clinically. It has generally been in presbyopic women ? some of whom were monocular monovision wearers where only the CL wearing eye developed GPC. Some were on limited EW or flexi-wear. Younger teenage patients have also shown more than normal levels of GPC and one would surmise their more active immune systems overreacted to the silicone and spat the dummy. The form of GPC I typically see in si-hy wearers seems different to what we saw in the ?old days?: SHPC seems more ?local? - over a smaller area of the ?central? tarsal conjunctiva and can develop quite quickly - while the ?old fashioned? type that appeared with ionic and non-ionic low Dk lenses generally developed chronically over longer-term wear and was more general or global in nature. This excellent article covers the issue rather well.
I would agree that the incidence of SHPC is greater in extended wear but I have seen too many in lower modulus si-hy versions to regard it as specifically modulus related. SHPC may not specifically be a ?modulus? issue but rather the fact that some of these lower modulus lenses are not plasma coated or surface treated so potentially larger areas of silicone are ?exposed? to the immune system. In the old days denatured protein was often blamed as the ?causative agent? and hence my interest in protein and lipid deposition. We know that si-hy lenses bind very little protein yet do bind considerable lipids. We also know that a plasma treated lens like Focus Night & Day binds less protein than non surface treated lenses. I suspect that more silicone is ?visible? to the immune system on non-surface treated lenses. The silicone-hydrogels website has many other articles and posters on the subject. Dig deep.
The bottom line is that it seems we don't really know for sure what GPC is all about, what the causative agents are for sure and I have yet to find a definitive paper on the subject.
Confused?
Well so am I, as are many others. I guess it leaves a gap for some classy researchers to do some ground breaking research with a novel study design that will help solve the riddle forever.
After thirty or so years I think It's about time.
Until then keep smiling, summer is almost here.

 

Forthcoming Attractions.

Next month I will once again feature a myriad of links to interesting websites. I've been doing these ?Best of the Web? editions for many years now. Although I have covered many great sites over the years (a few thousand in total), there are not a great number of great new sites. A few interesting new ones do however pop up from time to time and prove to be useful. Some duplication of links from previous years will occur but as the annual web feature serves as a useful ?one stop shop? to keep handy for instant links to websites of interest, I have repeated a few. Some sites are great for explaining things to patients while others will appeal to opto-nerds and enquiring minds.
I will include a fair few of those in addition to a spread of interesting academic, clinical and professional links and of course the odd irreverent site too.

Formula 1 is looking interesting at the moment.
Who will be crowned world champion?

 

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