As contact lens practitioners, we come across numerous complex cases. Many can be
managed these days with the fantastic variety of available high Dk disposable soft
lenses. Of course, where disposables fail, most cases can be corrected with RGPs.
There are, however, always a few curve balls to keep us on our toes. Some people are
simply RGP intolerant. Disposables may be out of the Rx range or simply do not work in
complex cases. Piggybacking and hybrid lenses can be a solution for some.
There are always a few cases where nothing seems to work.
That’s where modern specialty soft lenses come to the fore. I have trialed and fitted a few
very complex cases with some great results. In the next edition of Soft Special Edition, I
will present a case of one of my patients to illustrate this – with a life-changing outcome.
Some of these specialty soft lenses for keratoconus and other cases of irregular
astigmatism and for complex eye shapes and Rx are available in lathe-able silicone
hydrogel materials such as Contamac’s Definitive. (They can also be made in
conventional, high water content hydrogels.)
Why is Material Important?
Specialised soft lenses for irregular corneas are traditionally quite thick to start with (0.4
mm and thicker), and with a low Dk material there is close to no oxygen transmission
(Dk/L). I was thus always amazed by practitioners who promoted the use of ultra-thick,
low Dk soft keratoconus designs and, for that matter, first-generation hybrids. They just
didn’t cut the mustard, and many already compromised eyes suffered as a result of the
resultant physiological compromise, severe hypoxia, oedema, neovascularisation,
endothelial damage and corneal fatigue syndrome.
Although Dk/L is not massive in these high powered and thick soft lens designs,
Contamac’s Definitive si-hy material at least allows for a starting point of 60Dk, so thinner
parts of the lens may provide just enough oxygen.
Noel Brennan stated (in a recent lecture and in subsequent communication) that a Dk/L
of around 30 units would seem adequate centrally, but 50 units is more ideal. In the
periphery, around 8 units is an absolute minimum to prevent neovascularisation, but 30
units would be necessary to prevent any visible changes. I prefer around 50 units
centrally and about 30 or more in the periphery. A lens that’s 0.5mm thick in the periphery
will probably provide just enough oxygen transmission to avoid any complications. We
are, however, still rather borderline centrally with many of these complex, keratoconus
toric designs that are necessarily pretty thick.
So although way better than the low Dk, complex custom lenses of old, we still need to be
very careful and monitor these patients accordingly. As many will potentially need grafting
in the future, neovascularisation is a no-no: It will increase the future risk of graft rejection.
We must also always remember that these are compromised corneas, and thus
physiological stress should be avoided as far as possible.
One Small Step
Although a great addition to our armamentarium, these higher Dk, custom si-hy soft lens
materials are not the be-all, end-all, ultimate solution for keratoconus and other complex
cases. You can be sure that the R&D people are diligently working on the next step
forward. Thinner designs will of course perform much better: Hyperopic and myopic
astigmats will be also be much better off than in previous low Dk materials.
I’m against statements made by speakers who promote some of these lenses as ‘first
choice’ while knocking a badly fitted RGP in comparison. Others also take umbrage to
such comments. I’ve noted that consequently such strong promotional comments have
been toned down considerably. Where patients are RGP intolerant, then such lenses are
a great blessing. As always, it’s about balance.
The point is that higher Dk, custom si-hy soft lens materials are a great step ahead and
at least make such lenses a viable consideration.
Get with the Program
It’s in the best interests of independent and passionate practitioners to keep up with and
get the latest technology. In my experience, many chain stores are not geared to
specialised niche work; indeed I am told that they actively discourage these ‘time
A large behemoth such as a corporate chain takes time to change direction, adapt and
take on new products. This is where independent practitioners need to focus: They are
light on their feet and don’t have layers of international management to bog them down.
Of course we can still do the simple stuff, but straightforward cases are more likely to
migrate to the Internet and to mall-based, convenient, low-cost, special offer chains.
The way I see it, over the years optometry has largely lost much of the market. The
Internet is taking large chunks out of the contact lens market and deregulation is taking a
slice of dispensing work. Sunglasses and ready-readers are also a lost cause. Older
people are getting elective refractive cataract surgery as soon as they drop off quality 6/6,
and LASIK takes a fair chunk too. That leaves us with a few frustrated hyperopes,
astigmats and, of course, all the irregular and complex cases.
Specialist practitioners continue to do very well in areas of contact lenses, low vision,
learning disorders, pediatric vision, behavioural optometry, sports vision, acquired brain
injuries and so on.
The numbers may be down for some but we are not out by a long shot, and independent
specialist colleagues around the world tell me great success stories.
They remain passionate and focussed, as do their patients.
They continue to thrive!
Alan P Saks MCOptom [UK], Dip.Optom [ZA], FCLS [NZ] FAAO [USA]
Alan has served multiple terms as President of the Contact Lens Societies of South Africa
and New Zealand and arranged numerous conferences over three decades.
He is a recipient of a B&L award for outstanding achievement, has presented at various
conferences and has been a lecturer and examiner at a variety of optometry schools.
Alan has served on the editorial boards of several journals and his monthly column ‘In
Contact’ is subscribed to the world over. Alan writes for journals, websites and
manufacturers, takes part in protocol studies, international panels and acts as a consultant.