A wide range of topics and mix of research and education sessions proved a successful formula for the BCLA’s 2006 conference. In the first of two reports, Bill Harvey looks at what this year had to offer
Special sessions on public health and ocular risks, the latest silicone hydrogel lenses and a debate on the oxygen needs of the cornea were among the highlights of the BCLA’s annual Clinical Conference and Exhibition, held in Birmingham last month.
More than 900 delegates and around 1,200 visitors in total attended this year, with four out of 10 from overseas.
‘Orthokeratology….old devil or new saint?’ was the provocative title for the opening lecture on Thursday evening by Professor Dwight Cavanagh (Texas) and Professor Brien Holden (Sydney).
For Cavanagh, the question that lay at the heart of the current renaissance of ortho-K was: ‘What justifies the increased risk to benefit ratio of overnight wear?’ The ultimate benefit, he said, would be to prevent the progression of childhood myopia.
This potential benefit was so large that a randomised, prospective, masked clinical trial of ortho-K in children was justified, despite the possible increased risk of microbial keratitis. The best trial would be to measure the ortho-K effect in one eye against an alignment fit RGP lens of the same polymer in the other, he said.
Cavanagh’s assessment was that the future for ortho-K lay with very high Dk rigid lenses but Holden reported that soft ortho-K lenses would be more comfortable, better accepted by patients and offer better centration than RGPs. As to other approaches to controlling myopia, Holden coined the term ‘anti-myopic spectacles’ that would focus light on the peripheral as well as central retina and influence refractive development.
MATERIAL WORLD
Friday’s varied programme kicked off with Professor Brian Tighe (Aston, Birmingham) giving a useful review of silicone hydrogel (Si-H) development. Though occasionally a degree in biochemistry is needed to understand Professor Tighe’s lectures, this was an easy-to-follow description of how the excellent oxygen properties of silicone hydrogel material have driven researchers to overcome other inherent problems, such as poor wettability and high modulus.
He hinted that future developments in manufacturing volume, parameter range and surface properties could very well displace all other rival materials. Improvements in wettability, while still maintaining high transmissibility and lower modulus, were being addressed by the new comfilcon A material to which other speakers would refer as the day’s event went on.
Comfilcon A is the material in the new CooperVision Si-H lens about to be available in the UK and a description of its properties was given by Dr Arthur Back representing the company. The hope is that the naturally wettable surface without plasma treatment or coating will offer excellent comfort while still removing the threat of hypoxic response.
The potential problem of staining caused by surface treatments was alluded to by Professor Lyndon Jones (Waterloo) in his excellently informative review of care systems. Solutions have developed significantly from the days of chlorhexidine and thiomersol with their associated toxicity. Though hydrogen peroxide systems largely did away with toxic response, newer multipurpose systems (MPS) based on polyquad, polyhexanide or the newer alexidine or chlorite systems offered much in the way of improved wearer compliance and convenience.
Jones reported his observation of a ‘doughnut’ epithelial stain in some Si-H wearers using modern MPS and noted how care systems had not been developed in tandem with lens material, meaning that some combinations of MPS and Si-H lenses gave varying levels of epithelial staining. This was likely to be related to the surface properties of materials and future solutions are more likely to be tailored to Si-H materials. During the lecture, Professor Jones was one of the few to mention the recent association of ReNu with MoistureLoc with an outbreak of fungal keratitis which had forced a global product withdrawal.
Dr Jennifer Craig (Auckland) surprised some with her review of the various comparative advantages of different forms of visual correction, namely spectacles, contact lenses and refractive surgery. There was little new here for the audience, although she did mention an interesting paper from the Journal of Cataract and Refractive Surgery which noted that, while improved acuity in social situations remained the main reason for electing for refractive surgery, intolerance to spectacles and contact lenses remained a close second. This was a timely reminder of the significance of contact lens drop-outs which would be referred to again by many other speakers.
CRYSTAL, CLEAR?
Dr Joe Shovlin (Pennsylvania) raised the bar in his talk on corneal manifestations of systemic disease. This should have been compulsory listening for every pre-registration optometrist prior to their ocular disease exam. He explained how secondary corneal changes might be due to metabolic, immunological/inflammatory or infective diseases.
Metabolic disorders often gave asymptomatic ocular changes, but were usually multi-system so early diagnosis was essential. Changes might include corneal clouding (as with fucosidosis), whirling (Fabry’s disease) or crystalline deposition (cystinosis).
Immunological responses tended to be symptomatic, such as band keratopathy. Serum calcium levels could diagnose this condition well in advance of significant corneal clarity loss.
Of the many causes of infective systemic disease resulting in a variety of non-specific signs and symptoms in the cornea, Shovlin described an interesting case of corneal response due to ‘cat scratch fever’ which had initially presented with a retinal artery occlusion and surface phlycten - all this after a scratch from a kitten.
Crystal deposition due to cystinosis can look quite spectacular, but Shovlin also described how long-term therapy with gold for rheumatoid arthritis can also lead to crystalline deposition. Pretty as cystinosis may look to the optometrist, however, kidney involvement and a pigmentary retinopathy are also often present. Differential diagnosis is needed as conditions as serious as multiple myeloma can mimic cystinosis, though the crystals seen in myeloma are non-reflective and larger.
An important illustration of the need for careful history-taking was the presentation with multiple, apparently infective, corneal ulcers. It was found, however, after careful questioning that the patient was a serial cocaine user and this was the cause of the non-infective ‘crack cocaine keratopathy’. Tarsorrhaphy was needed.
A useful clinical pearl was the need to carefully examine presentations of superior limbal keratopathy (SLK). Unilateral and persistent SLK had been known to be, in fact, sebaceous gland carcinoma. Also it was often useful with SLK to get a thyroid check-up as there was an association with erratic thyroid hormone levels. A final tip for the gung-ho among you - in early suspect simplex keratitis, prednisolone was useful in ‘bringing out’ the condition for confirmation and treatment. Don’t tell the GPs.
DRY HUMOUR
Incoming BCLA president Chris Kerr next introduced the renowned Professor Charles McMonnies (New South Wales) as ‘from the colonies’.
Perhaps best known for his dry-eye questionnaire, McMonnies is also a great advocate of practitioner involvement in research. In the first of his presentations, he described how best to assess and therefore improve patient comfort. Citing that over half of patients drop out of lens wear due to discomfort, he then looked at possible causes.
It has been established that the tear film is thinnest inferiorly, leading to dry spot formation here. Forced blinking had been known to maintain lipid secretion from meibomian glands and to spread goblet cell mucin.
It is likely therefore that poor blinking is a significant factor in tear-film breakdown. Compared to the average seven micron tear film thickness, pre-lens tear film averaged only two microns, so dry spot formation was yet more likely.
He referred to several papers that suggested blink rates. In one, Professor Michael Doughty had suggested 10 to 22 per minute depending on environmental factors, while others had shown an average of around 20 blinks per minute, but this fell to just four per minute in computer users. A further suggestion was that up to 20 per cent of ‘normals’ had an incomplete blink rate.
Having established the importance of blinking and the value of information and advice to patients about adequate blinking, McMonnies went on to look at the finding that post-Lasik patients suffered ‘exposure staining both in the flap but also in the surrounding cornea’.
It was likely that the normal cornea was affected by the reduction in goblet cells caused by the Lasik, resulting in lower mucin levels.
A brief but lively presentation by Dr Inma Perez-Gomez (CIBA Vision) followed, which included a nice animation showing the basic process whereby PVA was incorporated into Focus Dailies.
She also provoked the crowd with her question, ‘Do you want to be a winner?’, while showing a picture of Barcelona winning the Champions’ League!
ALLERGY
Dr Noel Brennan (Melbourne) began his review of allergic eye disease with a semi-apology for his city being responsible for ‘two of the biggest troublemakers in the world - Shane Warne and Brien Holden’.
Around 30 per cent of the population have allergy of which around 60 per cent suffer allergic conjunctivitis. This could be classified into several options. Intermittent allergic conjunctivitis was the recommended term for what used to be called ‘seasonal’ (as many countries lack seasons), while persistent allergic conjunctivitis has replaced the term ‘perennial’. Vernal keratoconjunctivitis was a disease of young males, while atopic keratoconjunctivitis was more severe and often associated with skin conditions. In VKC and AKC, no specific allergen was identifiable. Contact ocular allergy (COA) may be the cause of solution response.
Brennan then gave a useful revision of the various hypersensitivity responses and listed which was involved for each type of disease: IAC and PAC (Type I), VKC, AKC and CLPC (Types I and IV) and COA (Type IV).
Treatments varied depending on severity but Brennan insisted he never advocated decongestants because of the risk of patient abuse and reactive hyperaemia.
He continued with a useful review of contact lens papillary conjunctivitis, mentioning how the aetiology was likely to be both allergic and mechanical, but was as yet still unclear.
Interestingly, it is now known that CLPC presents both generally across the tarsal plate but also, as in Si-H wearers, localised.
Localised CLPC seems to be the sign associated with the symptom of dryness, but not generalised CLPC. Ceasing lens wear was not a treatment option in Brennan’s view and, instead, daily wear and lens material and solution change should all be considered.
He finished with a plea to look at the bulbar conjunctiva, ‘the forgotten tissue’. Staining here matched well with dryness symptoms and lissamine green stain offered a useful method for optometrists to look for this sign.
- Part 2 of this report will appear on July 7 with an article on the exhibition appearing on June 9.
