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Implementing Evidence-based Clinical Practice in Optometry

Twa, Michael D.

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Optometry and Vision Science: August 2019 - Volume 96 - Issue 8 - p 539-541
doi: 10.1097/OPX.0000000000001414
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Most will be familiar with the term evidence-based medicine, and many will intuitively understand its basic principles—the application of clinical research to patient care. David Sackett, the pioneer who established this field, defined evidence-based medicine as “…the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.”1 There are three essential elements, each fundamental to evidence-based clinical practice:

  1. an understanding of each patient's individual values and preferences;
  2. a body of evidence that is relevant to the patient's unique circumstances; and
  3. an informed clinician exercising careful judgment on the interpretation and application of that evidence to the individual patient.


I have ordered these differently from their usual presentation. The first item, consideration for the patient's values and preferences, is most often presented last–implying that the patient's concerns are subordinate to the other considerations. Understandably, patient values and preferences can be wide ranging, and in most clinical practice settings, clinicians are often not encouraged or well prepared to elicit and discuss them. Because patient values and preferences are so individual, they are possibly the most difficult aspect of evidence-based practice to implement. Eliciting them can take time. Understanding them requires experiential training that often receives little emphasis on professional curricula, e.g., listening skills, cultural competency, responding to emotions, psychosocial and behavioral barriers to adherence, and more. Evidence-based practice has an impact only when it includes the patients as active participants in their own care and the decisions that determine their outcome. To fully embrace evidence-based practice, clinical training programs should prioritize adding opportunities to their curriculum where students can practice and develop experience with skills related to patient communication and critical thinking as it relates to clinical decision making.


Evidence-based practice in eye care is limited by the relatively shallow pool of available clinical trial outcomes and other forms of high-quality clinical research. The Cochrane Library is a public repository of systematic reviews: studies that aggregate, critically appraise the quality of clinical trial results, and summarize clinical research findings to provide current best practice recommendations to specific questions related to clinical care (e.g., Interventions for Recurrent Corneal Erosions is a Cochrane review on care for recurrent corneal erosions2). In comparison to other health disciplines, the evidence base for care of ocular conditions is not well covered. There are 39 total systematic reviews of results from 6700 clinical trials found when searching for titles that include Eye as a MeSH (Medical Subject Heading) term. For comparison, a search of the Cochrane library shows 114 systematic reviews from more than 16,500 clinical trials related to hypertension (MeSH: hypertension) and 755 systematic reviews of nearly 70,000 clinical trials related to cancer (MeSH: cancer). For evidence-based practice to advance and begin to influence the care of patients, we will need to expand the available clinical research evidence base. To accomplish this will require growing the number of clinician scientists actively participating in clinical research related to eye disease and visual disorders. It will further require institutional support from academic institutions that are willing to embrace evidence-based practice through teaching, research, and service. Likewise, scholarly societies should set expectations requiring evidence-based standards throughout their organizations, for example, membership requirements, postgraduate educational content standards, and definitions of advanced competency. Without the personnel required to help build the evidence base, as well as a cultural expectation that demands its use, meaningful growth in the body of clinical evidence and expanded implementation of evidence-based principles will be stunted and slow.


Implementing evidence-based clinical practice requires clinicians who are trained to do so. Present clinical training programs focus largely on other competencies that prepare students for entry to practice. Training programs rightly focus on clinical experience, procedural skills, interpretive knowledge, and judgment. Training in skills that support evidence-based practice is complementary and reinforces developing critical thinking and clinical judgment. In a previous editorial, I have discussed the PICO acronym as the common way that evidence-based practitioners are taught to ask structured questions.3 In brief, the PICO acronym stands for Patient (population or problem), Intervention, Comparison group, and Outcome. By identifying and carefully defining each component, one can develop a well-focused clinical question with a structure that can facilitate the next steps in evidence-based practice, namely navigation of appropriate information sources, and the accumulation of relevant evidence. For example, when caring for a patient with ocular hypertension, a provider may wish to know the risk of nonintervention. The structured question related to this clinical scenario could be this: What is the risk of developing primary open angle glaucoma for patients who do not receive treatment for ocular hypertension? In this case, the Patient group is those with ocular hypertension; the Intervention is no treatment (observation); and the Outcome is the rate of glaucoma among this patient group. Defining these three parameters delineates the clinical question and sets the search criteria (see Table 1).

Implementing evidence-based clinical practice

Even with a well-focused question in hand, navigating the evidence base is becoming increasingly complex. There are multiple resources that may be searched (Cochrane Library, PubMed, EMBASE, etc.) and also numerous tools to navigate these research repositories, from web browsers to commercial software specifically designed for conducting systematic reviews of the medical literature. While the task is conceptually straightforward, increasing sophistication is required to successfully navigate modern information resources. Training programs should provide instruction on this aspect of evidence-based practice because it will be critically important for graduates as they become independent learners in their postgraduate careers.

Critical appraisal of the accumulated resources come next as practitioners determine the relevance and quality of the discovered evidence. While training programs may didactically introduce hierarchies of evidence in the classroom (Fig. 1, e.g., clinical trials are above case reports), practical exposure to the evaluation of study designs, statistical methodologies, and control of bias should be reinforced and given context through the repeated application to specific clinical cases. In the end, practitioners must combine their accumulated clinical experience to make an informed, evidence-based decision, in collaboration with their patient.

Levels of evidence.

To advance the quality of eye care as a community of providers, we must address each of the components of evidence-based practice described above and summarized in Table 1. Discovery of the next new molecular mechanism of eye disease will not be sufficient by itself to improve eye health in the larger population. There are tremendous advances in public health to be realized from:

  • training providers in evidence-based practice methods;
  • enlarging the population of clinician scientists who can contribute to the accumulated evidence base;
  • expecting and encouraging peer-reviewed scientific contributions to the literature; and
  • encouraging evidence-based standards and practices within our communities (universities and academic societies).

Knowing the term evidence-based practice is only a small step along the way to implementing evidence-based care.

Michael D. Twa
Editor in Chief Houston, TX


1. Sackett DL, Rosenberg WM, Gray JA, et al. Evidence Based Medicine: What It Is and What It Isn't. BMJ 1996;312:71–2.
2. Watson SL, Leung V. Interventions for Recurrent Corneal Erosions. Cochrane Database Syst Rev 2018;7:CD001861.
3. Twa MD. Evidence-based Clinical Practice: Asking Focused Questions (PICO). Optom Vis Sci 2016;93:1187–8.
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