Letters: June 23

Show us the data

As someone who is happy to think the unthinkable, I am reluctant to challenge those who question conventional wisdom.However, Ron Hamilton’s arguments for fitting contact lenses over the web (Optician, June 9) leave a lot of unanswered questions and, more importantly, advocate an approach that seems recklessly unsafe.

The Daysoft web-based ‘brand matching system’ directs existing soft lens wearers to one of two Daysoft lenses based on their existing lens brand. Mr Hamilton is coy about how these choices are made on the basis that it is ‘company intellectual property’; however, after examining the web-based fitting process, it is difficult to understand where the intellectual content lies. The Daysoft website advises patients that all but two out of 20 or so competitive soft lenses are equivalent to the Daysoft 58 (single base curve).

When looking at specific examples of claimed equivalence, the assertions are even more baffling. How, for instance, can a relatively thick, dehydration-prone lens design be considered equivalent to a thin, dehydration-resistant, biomimetic lens? By my calculation, once equilibrated to eye temperature, the Daysoft 58 lens reduces in diameter to become about 0.5mm smaller than some of the other designs. According to the Daysoft website, the Dk/t of the Daysoft 58 lens is approximately 36 per cent lower than that of Focus Dailies which it professes to replace and, here again, with on-eye dehydration this difference will increase still further.

The twin assumptions underpinning this unsupervised switching of soft lenses are, first that soft lenses are a fairly unremarkable, standardised commodity product and, second, that the soft lens fitting process need consist of little more than a spherical refraction. Neither of these assumptions is correct – or why would the contact lens drop-out rate be so high?

It hardly seems necessary to point out, but ocular health will be compromised in those wearers who are refitted in an unsupervised fashion to poorly fitting or inappropriate soft lenses. The eye care practitioners involved in endorsing this scheme would be well advised to scrutinise the small print of their professional indemnity insurance policies. 

Mr Hamilton purports to have ‘robust’ clinical results to support the various claims of clinical equivalence but seems unwilling to share these. In fact, almost uniquely, no clinical data have been published on the performance of either of the Daysoft products. On behalf of his industry colleagues whose products he wishes to homogenise and on behalf of practitioners whose role he seeks to belittle, I challenge him to produce even a morsel of clinical data.
Graeme Young
Visioncare Research, Farnham