BCLA conference: Science in action

In the second of two reports from the BCLA’s 2006 conference, Bill Harvey and Alison Ewbank look at some of the research presented on the scientific programme and the special features at the event

After the first day’s patient-focused session, the lecture programme moved on to the latest research in contact lenses and the anterior eye and the presentation of work funded by the BCLA’s own research awards. The weekend also included various sessions running concurrently with the main programme for those with specialist interests.

Keynote speaker Professor Dwight Cavanagh (Texas) opened the second day’s lectures with an interesting, if at times a little difficult to follow, review of new investigative techniques used in corneal research. His team had used post-trauma light scatter changes to demonstrate that the cornea showed cellular (myofibroblast) changes after phototherapeutic keratectomy but apoptosis changes after a scrape injury, suggesting completely different healing processes.

He also mentioned how the Heidelberg II corneal module offered excellent high-resolution images of the various corneal layers and recommended that ‘once the instrument had been made more user friendly’, it should be of value to all contact lens and corneal specialists.
A new technique of non-linear optical imaging using multiphoton excitation of collagen fibres would revolutionise corneal study in the way that confocal microscopy did in the late 1980s. To back up this claim, Cavanagh showed some excellent video footage of the technique focusing through the many layers of a variety of corneas showing high levels of structural detail.

His team had also used gene tracking techniques to find that up to 15 per cent of corneal cells are bone marrow derived, suggesting our knowledge of corneal development needs urgent revision.

Dr Carol Lakkis (Melbourne) described a 12-month study of the performance of the comfilcon A material (the new CooperVision Biofinity lens). Comparing the material with balafilcon A (PureVision) and lotrafilcon A (Focus Night & Day) during 30-day wear, she concluded that it performed adequately within all the parameters measured. Her study found a significant increase in non-serious adverse responses for the balafilcon material, which she suggested might be due to the high modulus and the plasma surface treatment process. Comfilcon showed significantly higher (better) subjective rating scores than balafilcon, while comparable with lotrafilcon.

Dr Eric Papas (New South Wales) continued the theme with a highly enjoyable review of care product sensitivity, covering some of the same ground as Professor Lyndon Jones the previous day. He again noted that with second-generation silicone hydrogel (Si-H) lenses, some combinations of solutions and lenses showed significant staining. Although many authorities had dismissed this staining as innocuous, Papas did not accept this assessment and had conducted a retrospective study of more than 600 patients with a combined total of 24 different lens/solution combinations, 16 of which he had so far analysed.

He had indeed found that some combinations caused more toxic response than others, that ‘non-stainers’ were more comfortable and that more staining was associated with infiltrative events, albeit mild and asymptomatic. He concluded that staining and viewing with a Wratten filter was essential at every aftercare and that changes of lens/solution combination should always be considered in the presence of a response.

Dr Graeme Young reminded delegates of the significance of lens drop-outs, which were mainly due to discomfort, and then described a Johnson & Johnson sponsored study showing how refitting a sample of lens wearers with discomfort with the Acuvue Oasys had resulted in a halving of symptoms. He emphasised the problems of such studies, for example the possibility of a placebo effect when subjects were offered a new lens.

Professor Mark Willcox (New South Wales) gave an interesting review of his recent work on cleaning system action on protein and lipid deposition on Si-H lenses. He reminded delegates how protein led to allergy and inflammation, while lipid also could be a cause of inflammatory response. Si-H materials had also been found to deposit with lipocalin which was a common cause of allergic response. An ideal care product would, therefore, need to remove protein and lipid and also kill bacteria. His study had found that there was significantly less protein when a peroxide-based system was used, and that lotrafilcon lenses showed improved comfort with such a system.

Dr Kathy Dumbleton (Waterloo) compared overnight wear performance of the latest toric versions of the first generation Si-H lenses, made of lotrafilcon or balafilcon. She found little difference between them in terms of comfort and adverse response.