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The American Academy is always a fruitful source of new information with lectures, symposia, posters and presentations representing every aspect of optometry. Here is just a snapshot of some of the material of interest.
Glaucoma
Dr Mark Swanson (Alabama) has been looking at the association between smoking and glaucoma, noting that the previous association was reliant on self-reporting of the habit. A possibly more accurate indicator of exposure to smoking is the measurement of serum cotinine which is a secondary metabolite of nicotine. It does not show the great fluctuations that nicotine levels do and also may reflect passive exposure too. By analysing this data along with self-reporting of smoking, measurements of cup/disc ratio and FDT fields assessment, Swanson was able to deduce that in 5,603 patients there was no significant correlation between disc changes or fields results and cotinine levels, thus questioning the validity of smoking as a risk factor.
Private practitioner Dr Lisa Young has some concerns that the very process of assessment for glaucoma causes anatomical changes that may influence the accuracy of subsequent results. By altering the sequence of tonometry, gonioscopy, pachymetry, fields and nerve fibre analysis, she was able to show that the test sequence order resulted in differing corneal thickness measurements and this should be borne in mind - perhaps pachymetry before applanation?
A new study by Dr Nicole Stuebiger looking at 189 eyes confirmed that 'the rebound-tonometer is comparable with Goldmann applanation tonometry', which is good news for those of you, particularly the domiciliary optometrists, using the i-care rebound tonometer.
Obesity may have an association with glaucoma. Dr Michael Maizel (American Optometric Association) described the case of two obese patients who were ocular hypertensive and were not responding well to pressure-lowering drops. Both underwent weight reduction surgery and were found subsequently to have IOPs in the normal range without the need for any further topical intervention. This does hint at the interesting potential for systemic intervention with ocular hypertension patients.
A study by Dr Jessica Neuville (Kansas) compared glaucoma monitoring using SITA standard perimetry and the Cirrus OCT. She concluded that OCT measurements were correlated to visual function in early loss but they appeared to be a poor predictor of visual function at advanced levels of retinal nerve fibre loss.
Vision therapy
The effect and use of colour overlays to help with reading difficulties always seem a little hit or miss to me. Too much prescribing seems to rely on the anecdotal - 'what harm could they do?' 'they appear to work'. This does leave such intervention open to the accusation of being a mere placebo, albeit often an effective one. A paper from a team led by Professor Chris Chase (Western University, California) and including Dr Peter Allen (Anglia Ruskin) has found that reading difficulties are associated with weak accommodative function in a sample of students. In selecting a colour filter to ease their reading comfort, students tended to choose the colour most likely to reduce accommodative effort (such as a yellow or green filter). This may be evidence for the colour overlay reducing the accommodative lag and may be an explanation, at least in part, for why the filters often appear to work. It is important to remember that the impact on accommodative lag is likely to be small, however, of the order of a 10th of a dioptre or so.
A study by Dr Mitchell Scheiman (Pennsylvania) and his team looked at the effectiveness of vision therapy in the management of convergence insufficiency (CI). The trial looked at 221 children with symptomatic CI. Again, observation and anecdote would suggest exercises work but this is the first large-scale randomised trial of children with CI and accommodative dysfunction. Exercising is confirmed as effective and practice-based therapy (that is under the supervision of the practitioner) is more effective than home-based techniques. I suspect compliance is the issue here rather than the technique itself.
Another study in this area by German optometrist Marten Fortuin (along with City University stalwarts Professors Bruce Evans and Dave Edgar) found that orthoptic training was effective in the management of patients with CI or decompensated near exophorias, but also that compliance was a significant problem that impacts on success.
Anterior matters
The use of inserts as a means of providing a slow release treatment has been discussed for many years. A report by Dave Kading (Pacific) looked at the monitoring of dry eye in 418 patients. All completed a questionnaire assessment of their dry eye symptoms both at baseline and at 28 days. Not only were the scores correlative with clinician observations as well as symptoms, but also improved scores related well to the use of hydroxypropyl cellulose ophthalmic inserts.
There is still some concern about repeat use contact materials in optometry, such as gonioscopy lenses or reuseable tonometer prisms. In the US there are four approved methods of disinfection, including hydrogen peroxide soaking and the use of 70 per cent isopropyl alcohol (such as Mediswabs). A study by Jessica Carson (Missouri) found that the alcohol disinfection was not adequate to meet the required levels of sterilisation and also proposed that many optometrists failed to adequately sterilise the tonometer prisms.
It is some years now since Optician reported on the TearLab, a hand-held osmolarity test able to detect dry eye. It has never really found its market in the UK but still attracts interest at these sorts of conferences. A presentation about the instrument by Dr David Eldridge described how the test has now been granted a code recognising it as a valid clinical test and one that may be incorporated and paid for in a battery of anterior assessment techniques. Inter-eye differences of greater than 0.8mmol/l were a good indicator of dryness, he confirmed.
General health matters
Dr Daniel Roberts (Illinois) gave an excellent presentation on the very common condition pigment dispersion syndrome (PDS). He suggested that one of the reasons for an apparent hereditary component to the condition may relate to the fact that around 2 per cent of PDS patients have the trait for long anterior zonules (LAZ) and that those with such long zonules would show similar pigment changes but should be considered as a separate entity to the classic PDS patient. His studies had also suggested that long-term smoking was linked with LAZ expression.
With the UK Olympics on the horizon I suspect we will see a plethora of sports vision-related studies published in the next year. A study by Stephen Beckerman (again Illinois) had assessed the levels of eye care in participants in the junior Olympics of 2009 and compared them with those from 1998 to 1999. Vision assessment appeared to be increasingly important, as reflected in increased levels of eye care over the intervening decade, but there were still 29 per cent of athletes in 2009 who had undergone no eye care assessment for more than three years, and around 20 per cent of athletes had never seen an optometrist. He called for improved education among athletes to encourage regular eye care.
Nutrition
In an excellent symposium organised by the newly named Ocular Nutrition Society, speakers concerned themselves with the potential risks of harmful interactions. Dr Hans Bohlman (Texas) warned that practitioners should be extremely cautious recommending supplements with high vitamin A or beta-carotene to patients who smoke because of an increased risk of lung cancer. Also, vitamin B3 (niacin) is best avoided by patients already on statins as it increases the risk for liver or muscle damage. Patients already on anticoagulants might wish to avoid omega-3 fatty acid supplements as they may further heighten any anticoagulant effect.
Binocular vision
Some previous studies have suggested that CI is linked to reduced reading ability and this might in turn impact upon intelligence assessment scores. A study by Dr Lynn Mitchell (Ohio) found a mismatch between intelligence scores and reading ability in children with symptomatic CI and is now planning to look at the impact of CI training on reading ability.
Binocular vision studies tend to focus on the paediatric patient, but a study from Dr Susan Leat (Waterloo) analysed the files of 500 patients aged over 60 years and found the prevalence of binocular vision impairment to be very high (52 per cent). Leat suggested that the role of such an impairment in falls and physical injury was well worth further investigation, as such studies had previously concentrated on vision changes. ?
