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Age-related macular degeneration (AMD) is the main cause of sight impairment in the UK.
There is much increasing excitement - reflected in these pages earlier this year - about the potential of some new treatment methods for certain presentations of the disease. It is, however, always worth remembering that the vast majority of AMD is of the untreatable atrophic variety.
Furthermore, it is clear that an increasing percentage of the eye care professional's patient base will include AMD as the main reason for attendance in clinics. Optical help and vision training, along with advice and community liaison, are all important in the long-term management strategy. But with no treatments immediately imminent, the importance of risk factors and how to minimise them is attracting more attention.
It is gradually becoming common knowledge that smoking is the biggest controllable risk factor and practitioners certainly have a role here in giving appropriate advice. More and more research into short wavelength exposure and dietary factors adds to the list of what a practitioner can best recommend.
The inclusion of the carotenoids lutein and zeaxanthin in our diet is important. It is well known that these are found at the macula and appear to play a role in absorbing free radicals (and hence reduce the photo-oxidative process which damages the macular region) as well as having some protective effect against short wavelength radiation damage. If these are not readily available in the diet, through foodstuffs such as leafy green and yellow/red coloured vegetables, then many practitioners now recommend some form of supplementation with the intention of improving macular pigment density and therefore maximising any protective benefit against future degenerative maculopathy.
A reliable method of screening macular pigment density levels in patients might help to identify those patients where risk factor avoidance is particularly important, such as smokers, those with poor diet or exposure to short wavelength light.
The MacuScope
The MacuScope is an instrument designed with this aim in mind. It is about the size of an autorefractor and uses flicker photometry to assess macular pigment levels in patients (Figure 1 and see page 22).
The patient sits up to the machine and sees a fixation target which appears to be a blue flickering light. Fixating upon this allows the instrument to assess the foveal pigment density. The flicker slows down gradually and the patient is required to report when the flicker has stopped. This is a subjective test, so everything should be done to ensure that the patient responds as accurately as possible. A button is pressed once the patient has responded. A second target is then displayed which corresponds to the parafoveal region at eight degrees of eccentricity from fixation. The process is then repeated and the patient reports when the flicker is no longer visible. The macular pigment density may then be calculated from the ratio between the two measurements.
The display then shows the density along with a prediction as to whether it is low, medium or high (Figure 2).
MacuScope and MacuShield
The instrument is to be launched in January next year. It will be distributed by Birmingham Optical Group and the aim is to sell it to optical practices only. The predicted list price is £13,999, but a special promotion will be announced with the launch. The company will also supply the MacuShield supplement containing the meso-zeaxanthin pigment which was reported on recently (Optician, October 27, 2006).
? For further information on the instrument, contact Birmingham Optical Group on 0121 442 5800.