In Contact - February 2008

2008 has started off on the right foot. Although ?07 ended unspectacularly I did manage to harvest my first ripe tomatoes by the Christmas target. Auckland was as its best, sans many of its inhabitants who had headed to the beach. The weather turned great after New Year and we've had spectacular summer weather for three weeks. They reckon It's the best summer in a decade.
I concur.

Whats New?

CIBA?s O2Optix Custom is proving to be a good, flexible fitting system. I haven?t done many yet and cannot comment on long term results. The fIt's usually good. Time will tell how it behaves as far as GPC, SEALS and the like are concerned. Expect reduced complications when compared to the one-size-fits-all philosophy of some si-hy relatives: Provided proper fitting criteria are observed.
On the other hand, being a lens designed for extreme cases - many of which have been physiologically challenged for some time, we will still likely see a relatively higher incidence of certain complications.
Proper fitting means we need to follow the lens selection criteria of the ?old days? of conventional soft lenses. In the final three decades of the past century, a few great labs would make custom hydrogel lenses with 0.1mm steps in base curve, 0.2mm steps in diameter, in a range of water contents and materials. Centre thickness could also be specified, within physical limits.
Our favourite in those days was a custom Biogel 60, PVP-containing hydrogel. After thirty years a number of people continue to wear them successfully. Some labs still offer custom lenses and a number are trying to perfect lathe-cut custom silicone hydrogels that work and wet well. It looks like CIBA, with their exclusive lathing and patented plasma treatment have achieved it.
As a rule of thumb a cornea with ?average? K and eccentricity would need a lens fitted around 0.8 mm flatter than flattest K and around 2.0 mm larger than the HVID. Steeper corneas in general [which have more change in K from apex to limbus], hence greater eccentricity, may need lenses fitted 0.8 to 1.2mm flatter than flattest K. Similarly, flat corneas with low eccentricity may only need to be fitted 0.4 to 0.8mm flatter.
Hypoxia-induced myopia and astigmatism in will quite likely reduce after refitting. Even eyes that are within the Rx range of high Dk torics may be worth rehabilitating in a spherical lens as their corneas can sometimes ?bounce back? quite quickly. If the history shows low cyls around 0.25 to 0.75DC prior to HEMA lens wear commenced - with progression over decades of wear - then expect reductions after high Dk lenses. Many such cases of induced astigmatic progression to 1.25DC or more were then refitted into low Dk soft torics. This only induced further increases in corneal astigmatism as the cornea buckled and warped under the physiological burden of hypoxia induced oedema.
Again, as an anecdotal rule of thumb, one can expect around 10% reduction in myopia and as much as 20 - 50% reduction in induced astigmatism. I've done a case report on such a case on the siliconehydrogels website.
It's really only the extreme Rx patients that remain under severe hypoxic stress. They haven?t always had proactive practitioners and the benefit of high water and latterly si-hy disposables.
They do now. Fix it.

More to Come?

Can we now look forward to the arrival of a Custom O2Optix Toric, rumoured to be a possibility in late ?08? Or will O2Optix Toric be next on the cards?
Single use toric options continue to increase with a Biomedics daily toric to add to the already useful 1 Day Acuvue for Astigmatism, with its wide range of Rx options. Will we see a Moist version? One would think that logic would dictate that we do. The expanded Rx range in the pioneering Focus Daily Toric also adds to our armamentarium and is manufactured in the AquaRelease PVA-containing comfort enhancing material.
AquaComfort Plus has also debuted in Dailies sphere?s as an enhanced comfort version with moisturising agents HPMC, more PVA in the lens and added PEG [polyethylene glycol]. Interestingly the lens is made in 8.7/14 versus 8.6/13.8 parameters of the original daily.
In regular disposable torics Acuvue Advance for Astigmatism continues to provide excellent results. I've also been seeing a few Purevision Toric [PVT] wearers showing excellent results, three years down the track.
One can see the si-hy benefits in the form of whiter eyes, less dryness and reduced neovascularisation - particularly at six ?o clock where the prism ballast was a Dk weak spot in the low Dk torics of old.
We can look forward to the updated lower modulus B&L Purevision material gradually flowing through to Torics & Multifocals during ?08. This will likely increase my refitting into PVTs as a significant number don't always convert well from SofLens (66) Torics and other non si-hy lenses. Remember to instruct patients on an adaptation period and it is also often necessary to change solutions and care regimen. Most of the one?s I have wearing PVTs are daily wear but a limited number are doing well on EW.
Range and material enhancements - in a number or different lenses including spheres, torics, multifocals and maybe hybrids - are also expected during the course of this year. there's a growing body of one day options, re-releases, reworked lenses and enhanced materials.
Yet we still await a breakthrough high Dk daily.
It would also be nice to see some groundbreaking disinfecting systems and fool proof presbyopia options but don't hold your breath.
2008 thus looks like it will be a good year for contact lens practitioners as far as lens choices are concerned. I expect to see the swing to dailies, high Dk lenses and peroxide disinfection continue. ?08 will also focus on improving compliance via behavioural modification for manufacturers, patients and practitioners alike. EW will probably continue to decline in ?mature markets? as we have seen that the risks continue to be too high.
Dk has not solved all the EW problems. One could say the same for comfort. Dk didn't always fix that either. What it has fixed is hypoxia and for that we are thankful.
Contact lens evolution continues?
Lens and case coatings and other microbe resistant technologies will probably also start to raise their heads. In practical terms I expect that these will really only become available in the second decade of this millennium.
Here?s wishing you all a great ?08.

 

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