There is more to the tendency to develop contact lens-related keratitis than inappropriate wear and compliance issues. A large-scale analysis of swabs from 112 keratitis patients and 225 controls recruited at Moorfields and in Australia has shown that genetic variations of Defensin 1B lead to decreased protein expression of the gene hBD1. PhD student Nicole Carnt presented the findings, pointing out that this altered gene activity may increase susceptibility to and severity of keratitis in those patients exhibiting the activity and that further animal model studies of hBD gene activity may help explain the reason why some patients tended to corneal inflammation more than others.
In the same session Dr Lakshman Subbaraman explained how the release of the anti-inflammatory drug dexamethasone was influenced very much by the nature of the contact lens material used as the vector. Hyaluronic acid containing contact lenses released the drug at a much slower rate so showed great potential for future drug-delivery systems. Familiar BCLA stalwart Professor Mark Willcox described his work looking for any association between inflammatory mediators present in the tears and reported discomfort in contact lens wear. As yet, he explained, it would appear that there was no correlation significant enough to explain the mediators as a major influence on comfort.
Dr Stuart Richer, familiar to many for his work on diet and eye health, gave an excellent summary of what we know about the cornea as an indicator of systemic health. Using arcus as an illustration, he pointed out that the relationship between arcus and hypercholesterolaemia was not a straightforward one (for example, some ethnic groups such as the Inuit failed to develop arcus with advancing age) and arcus expression was likely to be influenced by the interaction of a whole array of factors ranging from simple cardiac bio-markers such as total cholesterol levels as well as external factors including anti-oxidants. His presentation went some way to show why many consider lesions such as xanthelasmata more reliable an indicator of systemic cholesterol levels than arcus itself.
Professor Jan Bergmanson, in his lecture on red eye management in contact lens wearers, emphasised that wherever permissible, the contact lens wearer should be allowed to continue to wear their lenses (if safe to do so) as this was their vision choice in the first place. For those able to introduce anti-inflammatory agents, the potential for adverse responses was an essential consideration when selecting the appropriate drug. He also noted how prudent use of topical prescription and non-prescription allergy agents might be sufficient to minimise activity of mediators such as histamine and keep the wearer in their lenses. Throughout his talk, he kept the patient's desire to continue wear at the forefront of many of the management options he described.
Focus on the eyelid
Several presentations focused on the importance of the eyelid in contact lens wear and related problems. Professor Richard Collin described the many congenital conditions that can influence subsequent eye health, many of which may be managed with strategies including contact lenses. Lid retraction, lagophthalmos (incomplete closure), distichiasis (extra lash row) ectropion and entropion can all result in a compromised cornea for which a contact lens barrier might prove useful. Ptosis can result in visual problems through deprivation amblyopia and often a combination of surgical and contact lens management might be appropriate.
With possibly the pun of the conference, Dr Graeme Young titled his talk on lids 'I get by with eyelid help from my friends.' He explained how the upper lid was particularly important in the maintenance of tear function and also in the maintenance of clarity, lubrication and optical clarity of contact lenses, not to mention their stability on the eye, important for spherical and especially toric lenses. He underlined how assessment of the lids must be an integral part of any contact lens evaluation.
The risk of corneal infiltrative events (CIEs) is highest among soft contact lens wearers in their late teens and early 20s. Dr Robin Chalmers told of some of the findings of the Contact Lens Assessment in Youth (CLAY) study group and suggested that college-aged soft wearers reported poorer general health, more exposure to water and higher density living conditions. As these were potentially modifiable risk factors, they might be considered when discussing lens wear with these groups to help avoid incidents of CIE.
Dr Robert Gerowitz, in a presentation serving as a useful aside to the myopia sessions discussed in the last article (Optician 06.07.12), explained how the ongoing SMART study continued to show after three years' follow-up that myopia progressed 'significantly less' in those 8-14 year-olds undertaking corneal reshaping with contact lenses as compared with those wearing silicone hydrogel standard lenses.
Dr Sheila Rae looked at tear film stability in wearers in 'indoor office' conditions (higher relative humidity) as compared with 'aircraft cabin' (lower humidity) conditions. It appeared that the tear film stability was more compromised in the office conditions whereas the tear meniscus height decreased significantly in the cabin conditions. She concluded that strategies to increase local humidity for the wearer in certain environments would be a good idea.
Dr Phil Morgan introduced a morning session dedicated to the use of fluorescein, how it works and how we might interpret findings from its use. He questioned the assumption that staining indicates loss or damage of cells and explained how a literature review revealed surprisingly little about how the dye worked or what it actually told us.
In an excellent review of the use of fluorescein, Professor Frank Bright explained how historically the dye has been used for purposes as diverse as monitoring river flow, helping to understand underground volcano activity and in the monitoring of cerebrospinal fluid flow. Its absorption and emission characteristics were very pH dependent and pH could alter activity by as much as 50 per cent. He went on to explain that the nature of fluorescein activity in contact lens wearer assessment was often governed by interaction of the molecule with the preservative present. Interaction with PHMB resulted in altered surface activity that might explain solution-induced corneal staining (SICS).
Professor Lyndon Jones gave a clinician-focused explanation of the recent interest in SICS (the majority of literature references to the phenomena appear in the last five years). He explained how the theory of fluorescein binding had led to the introduction of the term 'preservative associated transient hyperfluorescence' (PATH) and that there was debate over its significance. While many argued it was a transient effect, Jones explained how confocal microscopy studies indicated there might be more to it and that the staining observed at the slit lamp might actually fall somewhere between SICS and PATH.
Of the many short presentations, those that caught the eye included a talk by Anna Sulley who described a telephone questionnaire to more than 1,000 wearers that showed that approximately half of the vision corrected population were unaware that they had astigmatism and were often unaware of the existence of toric lenses - something for us all to consider in our practices when discussing contact lens correction.
A poster by Lee Hall looked at how the anterior OCT assessment of the cornea and sclera had shown that the cornea-scleral junction was steepest nasally and that topography varied with ethnicity between Asian and Caucasian subjects matched for age, sex and ametropia.
One workshop broke the mould this year. Delegates were transported from the ICC to Optegra Birmingham Eye Hospital and were treated to a workshop experience comprising a wet lab (with the opportunity to try out phacoemulsification and corneal epithelial debridement) as well as the chance to evaluate patients who had had a range of refractive procedures (including corneal laser refractive surgery, INTACS and refractive lens exchange). Delegates were also invited to try out state-of-the-art biometry techniques.
There was interest in the ProClear 1-day multifocal, but perhaps most interest was around the proposed launches in the UK of new one-day lenses from CIBA/Alcon and Bausch+Lomb. The launch of a high oxygen flux and biocompatible lens from B+L under the family name of BioTru was flagged at conference and the innovative material is likely to garner great interest.
Following on from Hall's findings, one interesting instrument was being showcased at the Carleton Optical stand. The Eaglet-Eye cornea/sclera topographer measures a 20mm zone on the anterior eye. Meibography was also the order of the day with several instruments incorporating an IR view allowing assessment of the meibomian gland patency. The Cobra includes such a facility, Topcon have a slit-lamp based system and the Oculus Keratograph in its latest incarnation is proving a popular choice for those investigating meibomian gland function.
With exciting new lens launches proposed there is likely to be great interest in next year's event due to take place in Manchester. ●