Diagnosing and Managing AMD – The Clinical Tools You Can’t Do Without

Age-related macular degeneration (AMD) is a major cause of vision impairment in developed countries.¹ While treatments exist for late-stage neovascular AMD, in the form of intra-vitreal vascular endothelial growth factor inhibitor injections, there are currently no approved medical therapies for earlier stages of AMD or late stage geographic atrophy (GA). Reducing progression to late stage disease is the best approach for decreasing vision loss and the associated individual and community burden of AMD.

This article provides an overview of the contemporary clinical classification of AMD, and discusses modifiable lifestyle risk factors that influence the progression of the disease. Additionally, it introduces a new, free, online clinical tool, the Macular Degeneration Clinical Care Audit Tool (MaD-CCAT), which will be launched at the Southern Regional Congress (Melbourne, May 2018), and is designed to assist optometrists with assessing the quality of eye care provided to their AMD patients.

The Clinical Classification of AMD

AMD is characterised by retinal changes that occur within a two-disc diameter radius of the fovea, in people aged 55 years or older. Early stages of AMD are indicated by the development of drusen, comprising of local accumulations of lipoproteineous material between the retinal pigment epithelium (RPE) and Bruch’s membrane. Drusen may be associated with changes to the integrity of the RPE, as demonstrated by retinal areas of hyper- or hypo-pigmentation. AMD can then progress to late stage GA of the RPE and/or choroidal neovascularisation (CNV); both forms of late-stage AMD can lead to significant central vision loss.

The MaD-CCAT enables optometrists to self-evaluate their practices with respect to the clinical care provided to people with AMD, relative to current evidence-based standards and guidelines

Historically, in the absence of universally accepted terminology, a number of clinical classification schemes were used to describe the severity and staging of AMD. Adopting a common definition and classification scheme is essential to enabling the consistent interpretation of findings for both research and clinical purposes. In 2013, the Beckman Initiative for Macular Research Classification Committee, comprising of a panel of international experts in AMD, published a key paper in the leading journal Ophthalmology to define a common clinical classification.² The AMD grading system outlined in this paper, which includes five categories based upon ocular fundus features, was constructed to be valuable for predicting a patient’s risk of developing late stage disease.² Table 1 summarises this classification system. An updated classification schema, including the interpretation of optical coherence tomography (OCT) findings, is expected in the near future.

*AMD pigmentary abnormalities denote any definite hyperpigmentary or hypopigmentary abnormalities associated with medium or large drusen but not associated with known disease entities;

125µm is approximately as wide as a major branched retinal venule crossing the optic disc margin.

As highlighted in a recent review paper,³ there are several key points worth noting about this classification scheme, as follows:

• The standard AMD staging nomenclature involve three stages: ‘early,’ ‘intermediate’ and ‘late’;
• The terms ‘wet AMD’ and ‘dry AMD’ are not part of the classification. The Beckman committee considered these descriptors to be potentially confusing, as ‘dry AMD’ has been previously used to describe AMD-related retinal changes ranging from isolated drusen to GA;
• Drusen are described by their size, at the smallest diameter, rather than by their subjective appearance; as such, historical descriptors of drusen, such as ‘soft’ and ‘hard,’ are not used;
• The classification scheme defines a ‘drupelet’ as a small druse, of less than 63µm in diameter;
• The presence of only drupelets within two disc diameters of the fovea defines a pre-AMD category of ‘normal
• ageing changes’, which is distinct from ‘early AMD’.

The Beckman classification also highlights the relative significance of macula pigmentary abnormalities for increasing the relative risk of AMD progression. The Age-Related Eye Disease Study (AREDS) found that eyes with hyper or hypo-pigmentation within two disc diameters of the fovea that did not have at least medium-sized drusen were at a relatively low (1.4 per cent) risk of progression to late stage AMD within five years.² The added presence of at least medium drusen substantially increased the risk of progression to late-stage AMD. The Beckman Initiative committee specifically defines “AMD pigmentary abnormalities” as “hyper or hypo-pigmentation present within two disc diameter (radius) of the centre of the macula, in eyes with drusen of 63µm or more in diameter and without known retinal disease entities or other reasons for such abnormalities.” The presence of AMD pigmentary abnormalities and/or large drusen (being more than 125µm at their smallest diameter), is indicative of substantial disease, and is thereby classified as intermediate AMD.

Late stage AMD is characterised by the development of CNV and/or GA within the macular region. Based upon ocular fundus appearance, GA is currently defined as a sharply delineated round or oval region, at least 175µm in diameter, in which the underlying choroidal vessels are visible.⁴ Neovascular AMD is indicated by subretinal or intraretinal fluid and haemorrhage at the macula; this may result from choroidal neovascularisation and/or sub-RPE or subretinal fibrovascular proliferation.³

Modifiable Risk Factors for AMD

The long term risk of vision threatening, age-related eye disease is influenced by modifiable lifestyle factors, in particular tobacco smoking and nutrition.

Tobacco Smoking

Smoking has been causally linked to several eye diseases, including cataract^5,6 and AMD.^7,8 Cigarette smoking at least doubles the risk of developing AMD;⁹ it is the single most important modifiable risk factor for the disease.¹⁰ A direct association exists between the number of cigarettes smoked over time and the risk of late stage AMD.¹¹ Although there is relatively strong public awareness about the systemic disease associations with smoking, including cardiovascular disease, cancer and stroke, the link between smoking and eye disease is generally less well appreciated.¹² To address this need for improved community awareness of the association between tobacco smoking and ocular pathology, the Australian Government has supported campaigns aimed at educating the public about the long term risk of blindness from smoking over the past decade. Public awareness programs of this nature have been shown to be valuable for altering smoking behaviours.^13,14

Over the past several years, researchers have sought to gain insight into the practices of primary eye clinicians in relation to whether they ask their patients about smoking, and whether they provide advice about the benefits of smoking cessation. Overall, findings from several studies, which have surveyed eye care clinicians in numerous countries,^15-18 including Australia,¹⁹ suggest there is the potential for optometrists to more proactively discuss smoking cessation with their patients. The potential barriers to undertaking smoking counselling, as identified by clinicians, include a perceived lack of time, a perception that there should be sufficient public awareness about the health risks and/or that questioning patients about their smoking habits was awkward or intrusive.¹⁹

To assist eye care practitioners with capturing key patient information about patient smoking behaviours and how these relate to a patient’s risk of AMD, in 2016 Dr. Laura Downie and A/Prof. Peter Keller developed a novel quantitative clinical smoking behaviour tool. The tool was created within the remit of Dr. Downie’s NHMRC Translating Research Into Practice (TRIP) Fellowship and is the first clinical tool of its kind for primary eye care clinicians. The tool consists of 10 elements that capture clinical information about patient smoking habits across three key areas:

(i) Current and former smoking behaviours (using a simple classification system to define smoking status) and how this relates to AMD risk (including the development and progression of AMD, and the predicted response to therapeutic intervention for CNV);

(ii) Smoking dependency, to quantify a current smoker’s level of nicotine dependence;

(iii) Motivation to quit smoking, to determine a current smoker’s readiness for smoking cessation, as quantified using a validated behavioural scale.

The tool then provides an evidence-based summary for each of these three areas, which practitioners can use to provide best-practice advice to patients about the benefits of smoking cessation for their ocular health.

Nutrition

Nutrition is another important area for possible AMD risk modification. As recently reviewed,²⁰ there is considerable epidemiological data supporting the potential benefit of a healthy diet, rich in the macular carotenoids (zeaxanthin and lutein) and omega-3 long-chain essential fatty acids (EFAs), for lowering the risk of late stage AMD. Furthermore, some patients who show ocular fundus features that confer a higher risk of progression to late stage AMD may benefit from the daily consumption of specific formulations of high dose antioxidant vitamins and minerals.^21,22 The decision to recommend such formulations to patients evidently requires consideration of the patient’s systemic health status, as well as the relative benefits versus risks of the intervention. For example, there is evidence from clinical trials funded by the National Cancer Institute that the risk of lung cancer is significantly increased with high dose beta-carotene supplementation in current and former smokers.^23,24

To promote the provision of evidence-based advice to patients in relation to diet and nutritional supplementation, and its influence on the development and progression of AMD, Dr. Downie and A/Prof. Keller also developed a quantitative clinical diet and nutritional supplement tool for implementation in practice. This simple questionnaire enables clinicians to capture key clinical information, related to a patient’s dietary behaviours across three main domains, which are relevant to the risk of AMD, as follows:

• Omega-3 essential fatty acid intake,
• Lutein and zeaxanthin intake,
• Nutritional supplement consumption.

Information derived from the survey can then be interpreted using a clinical key. This will guide optometrists when providing relevant evidence-based advice to their patients regarding dietary behaviours that promote a reduced risk of developing AMD, and to patients with progressive AMD.

The Importance of a Clinical Audit

In all fields of healthcare, a key component of evidence-based practice is a clinical audit, commonly defined as a “quality improvement process that seeks to improve patient care and outcomes through systematic review against explicit criteria and the implementation of change” (National Institute for Health and Clinical Excellence, 2002). In simple terms, a clinical audit involves finding out whether current care practices are appropriate, and identifying any potential shortfalls in patient care. It allows clinicians to assess whether they are adopting best practice, as defined by high quality clinical research. The ultimate aim of a clinical audit is to improve the provision of patient care.

Recognising a lack of audit tools available for optometrists to use, in 2015, Dr. Downie and collaborators Prof. Robyn Guymer, A/Prof. Peter Keller, Dr. Lauren Ayton and Prof. Algis Vingrys were awarded a Macular Disease Foundation Australia (MDFA) grant, for a project to develop an optometric clinical audit tool for assessing the quality of eye care provided to AMD patients. This audit tool, named the Macular Degeneration Clinical Care Audit Tool (MaD-CCAT) enables optometrists to self evaluate their practices with respect to the clinical care provided to people with AMD, relative to current evidence-based standards and guidelines. This process enables any potential areas for practice improvement to be identified that will enhance the quality and outcomes of optometric care for people with AMD.

The MaD-CCAT uses a free, online platform, to enable an audit to be easily completed using a computer, laptop or smartphone. The tool, which will be made available to all Australian optometrists, enables streamlined auditing of multiple dimensions of AMD care, including: the identification of modifiable risk factors (including smoking and diet) for AMD development and progression, accuracy of diagnosis, rate/timeliness of ophthalmologic referrals, referral accuracy and quality of record keeping. A representative snapshot of the system interface, in this case for the ‘Clinical diagnosis and findings’ screen, is provided in Figure 1.

Figure 1

Clinicians are guided through the audit process with step-by-step instructions. Data is captured using a check-box system, for rapid entry. For ease of data analysis, a summary statistics worksheet automatically populates key information comparing the practitioner’s current practices with current best-practice guidelines for the diagnosis and management of AMD. As audit data are progressively added, the summary statistics highlight areas of relative strength and potential areas for practice improvement. The practitioner can then identify key areas to change in their own practice, and develop strategies for implementing these improvements.

The MaD-CCAT will be launched at the Southern Regional Congress (SRC) in Melbourne, from 26–27 May 2018. Dr. Downie will present on the topic of ‘Optometric Management of Earlier Stages of AMD: Translating Research into Practice’ on Saturday 26 May, and will provide an overview of the MaD-CCAT, and the smoking and diet tools. The University of Melbourne also has a dedicated booth in the SRC Trade Exhibition (‘Clinical Tools – University of Melbourne’) to enable optometrists to register to use the MaD-CCAT, and experience live demonstrations of the system. Practitioner participation in a pilot program of the MaD-CCAT will attract therapeutic continuing professional development (CPD) points. For further information, optometrists can contact Dr. Laura Downie, [email protected] at the University of Melbourne.

Dr. Laura Downie BOptom, PhD(Melb), PGCertOcTher, FAAO, FACO, DipMus(Prac), AMusA is a Senior Lecturer at the Department of Optometry and Vision Sciences, Faculty of Medicine, Dentistry and Health Sciences, at The University of Melbourne.

References

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