Ophthalmic Epidemiology OER – Part1. Basic Principles

Discover the key concepts of epidemiology for eye care, explore the causes and distribution of visual impairment in populations, learn about key epidemiological study designs and assess their strengths and limitations for studying eye disease.

 

Materials from the course are published under a Creative Commons license (CC BY-NC-SA-4.0) which permits non-commercial re-use without asking for permission. We encourage you to download, adapt and share these Open Educational Resources (OER) for teaching and learning.

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Week 1 Epidemiology and eye health: An introduction

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Week 2. Measuring disease frequency and association

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Week 3. Study designs and sources of error

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Week 1: Epidemiology and eye health: An introduction

Key concepts in epidemiology for eye care

Discover the history and definition of epidemiology for eye care and the definition of prevalence – a key term in epidemiology. Consider why it’s important to share a definition of visual impairment and conclude by examining the epidemiology of visual impairment globally and in the context of The Gambia.

Video: Welcome to the course and session 1

Dr Daksha Patel, lead educator, introduces the course and the topics explored in week 1

Video & teaching slides: An introduction to epidemiology

In this step, we give a brief history of epidemiology and how it enables a health provider to take evidence based action. In particular, we look at the important work in 19th century London on the epidemiology of cholera  by John Snow.

Video & teaching slides: An introduction to prevalence

In this step, we introduce prevalence, a key term in epidemiology. Prevalence is commonly used to signify the magnitude of a disease, or condition, and answer the question of “how many?”

Video & teaching slides: Defining visual impairment

In this video we look at the World Health Organization’s (WHO) classification of visual impairment, which will be used throughout the course.

Video & teaching slides:  Epidemiology of visual impairment

In this step we introduce the epidemiology of visual impairment and blindness and look at four key concepts. Magnitude – how many people are affected?, Distribution – where is it?, Determinants – what are the main causes and Control – what can we do about it?

Article: Epidemiology of visual impairment in The Gambia

This step encourages the discussion of The practical application of prevalence data

Video & teaching slides:  The Global Action Plan and VISION 2020

Scaling up global eye care through Universal Eye Health and the eye health systems approach


Week 2 : Measuring disease frequency and association

In this week we examine the key epidemiological measures of disease frequency and association: cumulative incidence and incidence rate.

Article: Welcome to session 2

Video & teaching slides:  What is incidence in epidemiology?

In this video we introduce and look at how to calculate the two main kinds of incidence; cumulative incidence and incidence rate.

Video & teaching slides:  How to calculate incidence

In this video we explain the essential steps required to calculate cumulative incidence and incidence rate through five examples looking at the incidence of myopia in children in Singapore.

Video & teaching slides:  The effect of exposure on incidence

In epidemiology, studies are undertaken to examine whether certain factors are associated with diseases.  If there is an association between a factor and a disease, it would then be called a risk factor for this disease.  In this step we consider how a factor may or may not be a risk factor for a disease.

Article: Understanding 2×2 tables

Visualising possible relationships between disease and exposure

Article: Practical application of incidence – ROP study in England

Article: Study of cataract blindness incidence in India

Examining the practical application of incidence data


Week 3: Study designs and sources of error

Different study designs answer different questions

In our final session we introduce the key epidemiological study designs and assess their strengths and limitations. We then go on to consider how different study designs are used to address specific research issues in eye care. We conclude with reflection and discussion on the content covered and ways you can take your learning forward.

Please take a few minutes to complete the post-course survey. This will help us understand your learning experience and improve the course.

Article: Welcome to session 3

Video & teaching slides:  Linking research questions and methods: Part 1?

Professor Clare Gilbert of the London School of Hygiene & Tropical Medicine begins this presentation by giving a brief overview of the basics of public health. She then introduces us to the fictional case study of Bronoland – a typical regional setting in many low income countries.

Video & teaching slides:  Cross-sectional studies?

The cross-sectional study, often known simply as a survey, is the most popular study design. When carrying out a cross-sectional study, we collect data about a population at risk, at one specific point in time.

Video & teaching slides:  Linking research questions and methods: Part 2?

In the second half of Professor Gilbert’s presentation, she continues to explore the selection and use of epidemiological methods to answer key research questions

Video & teaching slides:  Other study designs

In this step we complete our introduction to the main study designs used in epidemiological research by looking at some other useful study designs: case control studies, cohort studies, randomised controlled trials and qualitative research methods.

Video & teaching slides:  What is bias?

Bias is defined as a tendency towards an unreasonable, or prejudiced, consideration of a question.

Article: Understanding sampling

In this step, we introduce the principles, purpose and types of sampling methods that are used in epidemiological studies in eye care.

Video & teaching slides:  What is confounding?

Bias arises from flawed information or subject selection so that an incorrect association is found. Confounding distorts the true association between the exposure being studied and the disease

Video & teaching slides:  Conclusion

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