It was rather apt that CIBA Vision should hold a workshop extolling the benefits of air, or more precisely Air Optix, in Scotland, a country which has recently adopted a fresh air policy by banning smoking in all public places.
Three presentations were supplied, in combination with the tried and tested interactive keypads to promote maximum audience participation. Before the first presentation an outline of the audience views indicated that 9 per cent were unhappy to fit extended wear, so the challenge was on for CIBA Vision to inform and discuss and hopefully change the opinions of the 'doubting Thomas' delegates in the audience.
EOP versus Flux
Rob Terry (CCLRU) introduced us to silicone hydrogels and indicated we should 'offer the best' to our patients.
He discussed the evolution of extended wear, from gas permeable lenses, through silicone elastomers, to present day second and third generation silicone hydrogels.
From a research point of view he suggested the equivalent oxygen percentage (EOP) that is beneath a contact lens on the eye gives more information than Dk or Dk/t, which is effected by lens design and back vertex power. He also favoured EOP over oxygen flux as he felt the latter can be confusing. He pointed out that flux values calculated as equal for different lenses do not produce the same consequence for corneal health. For Night & Day lenses there is an EOP of 20 per cent (open eye) and 5 per cent (closed eye) compared to a traditional 58 per cent water content lens with an EOP of 11 per cent (open eye) and 1 per cent (closed eye).
But how does this relate to every-day practice? The interactive keypads indicated we were familiar with the physiological problems associated with hypoxia (corneal swelling, epithelial microcysts, stromal thinning, endothelial polymegathism and myopic creep), except most of the audience did not know that microcysts represented dead cells, so how do high-DK lenses help? They maintain epithelial homeostasis by minimising disruption of basal cell proliferation and squamous cell shedding, while reducing corneal oedema and endothelial changes. Terry described how no lens wear induces 3.2 per cent overnight corneal swelling which requires a minimum of 125 Dk/t, the critical value suggested by more recent research. Air Optix has a Dk/t of 138.
The next presenter was Brian Tompkins (private practice, Northampton) who introduced himself as a proactive contact lens fitter who gets excited about new innovations. He presented two case studies of patients wearing Air Optix lenses under the theme 'It does exactly what it says on the lens', namely comfort, convenience, good vision and the highest silicone hydrogel Dk/t. He has also performed a practice trial on Air Optix Toric and looked forward to the UK launch of these next year.
He explained that silicone hydrogels account for 14 per cent of new fits and 32 per cent of refits in the UK. His message was that these lenses are not just problem-solving but problem-prevention lenses. He did, however, emphasise the importance of an explanation of any complications (CLARE, microbial keratitis, CLPU and infiltrative keratitis) to patients and to be aware of the warning signs. These are outlined in literature he gives to all his patients and can be downloaded from www.siliconehydrogels.org
Drying Tonight!
The final presentation, again by Terry, was more marketing based, discussing how to thrive in the silicone hydrogel lens wear market.
The obvious benefit, of reducing the 'Bride of Dracula' conjunctival congestion, was commonly known but the benefit for patients with dry eye due to low water content was not. He could, however, have better emphasised the fact that any lid problems (such as meibomian gland dysfunction) should be resolved prior to giving a silicone hydrogel trial to reduce dry eye sensation. He emphasised that patients should earn the right to evolve from daily wear to extended wear silicone hydrogels and phase this in after at least two months' daily wear without complications.
My only slight criticism about this excellent presentation was that, although delivered well, the overall message could equally have been given by a professional service representative from CIBA Vision.
In summary, the audience electronic questionnaire was repeated and the 'doubting Thomas' delegates who would still not be happy fitting extended wear reduced to 3 per cent. This trend towards nearly all practitioners being happy to fit daily wear, but with some reluctant to fit extended wear silicone hydrogels, represents a longstanding profile which is gradually being eroded. Seminars, such as this one partly explain this attitudinal change, and are to be congratulated.
There are soon to be six silicone hydrogel lenses available on the UK market (Advance, PureVision, Air Optix, Biofinity, Oasys and Night & Day), some with dedicated solutions. So watch this space for an evolution in contact lens practice that is happening right in front of our eyes.
Dr Scott Mackie is an optometrist in private practice