Macular Degeneration

The first step in the evidence-based practice process is the formulation of an answerable clinical question. This involves identifying terms that can be used in a search for information (evidence) that will help to answer the question. The acronym “PICO” is widely used as a framework to help clinicians identify those search terms. PICO stands for:

P: Patient, Population or Problem. This is a term that identifies the type of patient and/or the condition or problem of interest.

I: Intervention. This term describes the intervention or treatment of interest.

C: Comparison; indicating any state with which the intervention of interest is compared, e.g. a placebo.

O: Outcome; the outcome measure.

The PICO acronym works well for many clinical scenarios in which we are considering intervention or treatment of a condition. However, not all of these terms apply when we are considering scenarios in which we are interested in; diagnosis, prognosis or prevalence, for example.

For the clinical scenario described below, a number of different clinical questions are considered and derived. In each case, modifications of the standard PICO format are considered:

A 46 year old Caucasian female patient in good ocular and systemic health and with nothing significant in her family history tells you that she heard on about age-related macular degeneration on a radio programme. She was worried by the possibility of acquiring this condition and would like to find out the likelihood of this happening. She later saw an advertisement in a magazine for nutritional supplements that can help prevent this from happening. 
Duration

30 minutes

Level

Beginner

Authors

Elizabeth Murray

Audience

Optometrists
Students
Teachers

  • In advising the patient and in anticipation of the need to advise other patients, you wish to:

    • Advise the patient on the causes of age-related macular degeneration
    • Put the possibility of acquiring the condition into perspective with prevalence data
    • Be able to determine whether there are any early signs of macular degeneration in this patient
    • Provide advice on the benefits and any potential for harm in taking nutritional supplements
    • Provide information on the rate of progression of the condition and the impact of age-related macular degeneration on independent living.
    Advise the patient on the causes of age-related macular degeneration:

    You want to be able to provide the patient with reliable information on the risk factors for age-related macular degeneration. This is an aetiology question, and in this case we have a ‘P’ for patient and problem, and we are interested in risk factors, which will be denoted here by ‘R’. We have a bit of overlap between age-related macular degeneration being a ‘P’ problem and an ‘O’ outcome. We could use both P and O if that makes the situation easier to understand; the important point is that the outcome and the problem should be stated, and it is fine in this aetiology question to think of the condition as being both a problem (P) and/or an outcome (O). Note that in the question below, ‘O’ is the development of the condition.

    Suggested question: “What are the risk factors [R] for development [O] of age-related macular degeneration in Caucasian females [P]?” 

     
    Put the possibility of acquiring the condition into perspective with prevalence data

    You want to tell the patient how prevalent this condition is in her population. We need to construct a clinical question that includes the elements we will need in order to carry out an efficient search of the literature for information that can help provide a reliable answer. In this case, the ‘I’ (intervention) and ‘C’ (Comparison) terms of PICO are not relevant. We need to modify PICO to include elements that are relevant to this question. We need to retain ‘P’ (Patient, or Population) so that we include indicators of the patient type to narrow our search to this type. Instead of ‘I’, ‘C’ and ‘O’, we can use an ‘N’ (Number) term here, to represent Prevalence or Incidence. Thus, our question needs to include terms describing the Patient/Population and a term indicating Number, for prevalence.

     

    “In middle-aged Caucasian females, what is the prevalence of age-related macular degeneration”. Alternatively, we might want to be more realistic and ask about the prevalence without specifying age, since the condition is likely to be rare at middle age: “In Caucasian females [P], what is the prevalence [N] of age-related macular degeneration [P]?”

    In this case we have diagnosed myopia progression, but how was this diagnosis made. I asked an academic with research expertise in this area "What are the criteria for diagnosis of myopia progression" and the (tongue in cheek) answer was "It's getting worse". So, the diagnosis is likely to have been on the basis of some degree of myopia increase over time. You might be interested in finding out how much or how rapid this increase needs to be in order to be given a "progression" label.

    To look into this, you would need to ask a question about diagnosis. Not all of the PICO terms would apply, since we have no intervention (I). For diagnostic accuracy, we would usually have a gold standard and this would be our comparison (C). This case is an example in which there is not an accepted gold standard, so we may want to ask a more open question in which we specify a diagnostic test method (T) with no specified comparison (C).

    Suggested question about criteria used to diagnose myopia progression:

    What criteria are used in the diagnosis of myopia progression in children?

    Alternatively, the following question is more specific:

    Is progression rate of 1D per year a reliable criterion for diagnosis of myopia progression in children?

    We are interested in the progression of myopia in children, so we have P (both problem and patient). We may want to know about prognosis in terms of the pattern of progression, with no intervention or with a specified intervention. If we specify intervention we may specify an intervention (I) and a comparison (C). If not, we do not need to use a comparison term.

    Our question might be: In children with progressive myopia (P), what is the pattern of progression into adulthood (O)? Alternatively, we may want to ask: In children (P) taking antimuscarinic topical medication (I) to reduce the rate of myopia progression (P), what is the pattern of progression into adulthood (O) compared with refractive correction only (C)?

    This is a question on intervention, so all of PICO can apply. We have the patient or problem (child with myopia progression), the intervention, a comparison intervention (if we choose to specify one) and the outcome (reduced rate of progression).

    Suggested question: What is the efficacy of methods (I) intended to slow the rate (O) of myopia progression in children (P)? No particular method is stated here, and so there is no comparison method.

    Alternatively, we could choose a method that purports to slow myopia progression, and name this in the question, and we could also name a comparison method if we wish. For example: Suggested alternative question: What is the efficacy of antimuscarinic topical medication (I) to slow the rate (O) of progression of myopia in children (P) Or a question including comparison: What is the efficacy of antimuscarinic topical medication (I) compared with undercorrection (C) to slow the rate (O) of myopia progression in children (P)

    What are the risk factors [R] for development [O] of age-related macular degeneration in Caucasian females [P]?

    A good secondary source is the Cochrane Eyes and Vision database. To search sources of this kind, and for original research (primary sources) via Pubmed appropriate key words are needed, based on the question formulated in step one. In this case key words might be: risk factors and age-related macular degeneration. However, a Pubmed search using these terms at the time of writing yields 1789 results, so the search should be more specific. Adding the term “white female” reduces this number to a much more manageable 84. However, it is highly likely that a topic of this kind would have several Cochrane reviews, and in fact at the time of writing several such reviews exist, so the initial search of this secondary source is likely to be fruitful.

    In middle-aged Caucasian females, what is the prevalence of age-related macular degeneration.

    A good secondary source is the Cochrane Eyes and Vision database. To search sources of this kind, and for original research (primary sources) via Pubmed appropriate key words are needed, based on the question formulated in step one. In this case key words might be: prevalence and age-related macular degeneration. Using these terms in a Pubmed search at the time of writing yields 2061 results, but with “white female” added this reduces to 115, and with “Australia” further added, 14 results.

    In Caucasian middle-aged females [P], what is the sensitivity and specificity of optical coherence tomography [T]compared with grading of fundus photographs [C] in the diagnosis [D] of for age-related macular degeneration [P]

    A good secondary source is the Cochrane Eyes and Vision database. To search sources of this kind, and for original research (primary sources) via Pubmed appropriate key words are needed, based on the question formulated in step one. In this case such key words might be: sensitivity; specificity, optical coherence tomography; digital photographs and age-related macular degeneration. However, this would be a very specific search and may not yield many, if any, papers. It may be necessary to exclude some of these key words for a broader search. On a topic of this kind, a search of the Cochrane reviews is likely to yield results, and in fact at the time of writing reviews relating to the diagnosis of this condition are available, so the search of this secondary source may mean that a primary source search is not necessary.

    In white females [P], how does age-related macular degeneration [P]affect quality of life [O]?

    A good secondary source is the Cochrane Eyes and Vision database. To search sources of this kind, and for original research (primary sources) via Pubmed appropriate key words are needed, based on the question formulated in step one. In this case key words might be: quality of life and age-related macular degeneration. At the time of writing a Pubmed search using just these terms yields over 400 results. The Person type is not represented in these key words, and for a more specific search the key words “Caucasian females” or “white females” could be added.

    A suggested question is: “In middle-aged white females [P], are nutritional supplements [I; specific supplements could be named here]effective in the prevention of age-related macular degeneration [O]

    A good secondary source is the Cochrane Eyes and Vision database. The BCO clinical guidelines also provide a good secondary source to support clinical management questions of this kind. To search sources of this kind, and for original research (primary sources) via Pubmed appropriate key words are needed, based on the question formulated in step one. Appropriate key words include: nutritional supplements; prevention; age-related macular degeneration. Note that there are Cochrane reviews on the management of this condition, so the secondary source search is likely to find good, high level evidence relevant to this question.