The age-related macular disease eye care pathway

Approximately 70 per cent of people included on the blind and partial sight registers for the UK are over 75 years of age. Macular degeneration is the most common cause, accounting for approximately half of registered cases.1
With the management of systemic disease improving, it is expected that the number of elderly within our population is set to rise even further. The Department of Health has estimated that the total number of visually impaired is set to rise by 25 per cent in the next 20 years.2
One recent study3 looked at a population of 1,742 visually impaired, all aged 75 years or over. Interestingly, in 26 per cent of cases the cause was uncorrected refractive error - a useful reminder that optometric services in the UK are not necessarily available to all. A massive 52 per cent had impairment due to macular degeneration, way ahead of the numbers with cataract (35 per cent), glaucoma (11.6 per cent), myopic degeneration (4.2 per cent) and diabetic eye disease (3.4 per cent).
This pattern will undoubtedly have the effect of a greater demand for services for visually impaired people, which will include the provision of low vision aids. On the other hand, there have been some significant developments in the understanding of macular disease and this has led to the development of new treatments for some presentations of the disease. In the coming years, more still is likely to be possible regarding treatment as drug intervention and prophylactic measures become more formally acceptable.
In view of the statistics and treatment implications, it was not a surprise that AMD was singled out as relevant to the new eye care pathway proposals. A further, often forgotten, point is that visual impairment (and therefore AMD) is a major contributory factor in falls and accidental injury. The burden on the health service because of this is significant. One might then further consider the impact the disease has on loss of independence, leading to a burden on social services, not to mention the impact on loss of earnings now that the age of retirement is less defined than for former generations.
The AMD Steering Group
The chair of the AMD Pathway Steering Group is past-president of the College of Optometrists, Frank Munro. When speaking of the importance of the condition, Munro is always keen to cite examples of the effects this common disease has had on people around him. Sometimes it is important to remind everyone of the personal impact of a condition; the statistics, stark as they are, often tend to objectify but dehumanise the impact.
What the group has identified is that there is already much in place to be commended in terms of AMD screening and management. To all intents and purposes, it is part of the role of an optometrists anyway to screen the maculae of patients and then to decide upon an appropriate course of action when disease is suspected.
The issue, as ever, is with a less than standardised service around the UK. Access to one of approximately 7,500 optometrists in the community is good, though less so for the increasing numbers of elderly housebound patients. Optometrist training (initial and continuing) should allow for all to be able to identify and differentiate the various presentations of AMD at an early stage, but some surveys have suggested that, much as we would not like to hear it, this is not always the case. Furthermore, where early choroidal neovascular activity ('wet' AMD) has been identified, in some areas access to fluorescein angiography and possible photodynamic therapy is good and rapid, less so in other areas. If a longer-standing atrophic AMD is becoming a burden on somebody's quality of life, readers of this journal will be more than familiar with the fact that access to low vision services is very variable from area to area.
The recommended pathway is an attempt to highlight these issues and ultimately lead to a national standard whereby all requiring screening may have access to regular review by optometrists of a recognised competency who may then be able to act in a triage-like role. The first triage is to decide if AMD is actually present. If not, then any other pathology should be acted upon in the same manner as usual for an optometrist. If AMD is identified, then a second triage may involve deciding on whether the disease is CNV or strophic, the former requiring rapid referral for assessment and possible medical intervention, the second management exploiting the new proposed referral pathway for low vision.

The core competency requirements for screening for AMD must include the following:

Full and relevant patient history, with particular regard to the nature of any central vision changes
A full refraction, noting any loss of acuity and hypermetropic shifts (a finding in early retinal pigment epithelium elevation at the outset of CNV)
Full slit-lamp biomicroscopy, essential for a detailed and three-dimensional assessment of the macular area
Amsler assessment with particular interest in the nature and extent of any distortion found
Any co-morbidity needs to be identified before the diagnosis and management are decided upon.

Munro has argued that further assessments that might be useful would include digital image capture of the macular area, useful for subsequent monitoring of the condition. Photostress testing, the ability of the eye to recover after a bright light flash, is also useful and widely used in the US as a means of assessing macular function. Contrast sensitivity assessment is also a useful indicator of the impact upon vision of the disease. As mentioned on page 37, hyperacuity perimetry is a developing science which may well become the norm in AMD screening programmes.
The message, it would seem, is one of improving what is already showing good results in the challenge to reduce the impact of AMD upon an ageing population.

References
1 RNIB: Estimates and Registration Statistics for the UK 1995.
2 Ryan B, McCloughlan L. (1999) Our better vision: what people need from low vision services in the UK. London. RNIB.
3 British Journal of Ophthalmology, (2004);88:365-370.