Global Blindness: Understanding refractive error
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Uncorrected refractive error is a major cause of visual impairment in the world after cataract. Estimates from 2004 indicate that over 8 million people are blind and over 145 million are visually impaired because they lack refractive correction. In this presentation we define refractive error in the context of public health and describe its epidemiology. We then go on to explore the factors which affect refractive error service delivery and school health programmes. © 2016 International Centre for Eye Health, London School of Hygiene & Tropical Medicine. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license. Taken from the free online course: Global Blindness: Planning and Managing Eye Care Services. We encourage the use and adaptation of this resource for teaching and learning. Find more Open Educational Resources for eye care on our website at http://iceh.lshtm.ac.uk/oer
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Global Blindness: Understanding refractive error
- 1. Global Blindness: Planning and managing eye care services Understanding refractive error
- 2. Learning outcomes Define refractive error and describe its epidemiology Explore considerations for service delivery at community level Appraise school health programmes and their management
- 3. Refractive error is a presenting visual acuity of < 6/18 which can be corrected by refraction or by pin hole - temporarily
- 4. Correctable myopia is worse than -1 dioptre Correctable hyperopia is +3 dioptres or more Correct astigmatism of 1.5 dioptres or more
- 6. Uncorrected refractive error is the second major cause of blindness and low vision in the world 8 million blind 145 million visually impaired
- 7. Who is most affected by refractive error? In children aged under 15, higher prevalence found in urban areas
- 8. Who is most affected by refractive error? 94 million people aged over 50
- 9. The largest burden of refractive error is in India and China More research is needed
- 10. Why is there so much refractive error? Lack of vision testing for children Lack of refractive services Limited affordability
- 11. Why is there so much refractive error? Sometimes spectacles are not regarded as essential Cultural disincentives
- 12. Impact of visual impairment from refractive error Isolation and fewer opportunities Limited educational performance and success
- 13. Impact of visual impairment from refractive error Lower quality of life and poverty More exposure to morbidities and higher mortality rates
- 14. Two strategies for improving access Plan for a population of 50,000 Focus on increasing demand and supply
- 15. Primary level
- 16. Estimating demand for spectacles Calculate from prevalence data for the target population
- 17. Estimating demand for spectacles Where no data is available, 20% of the total population is reasonable estimate
- 18. Creating demand: social marketing
- 19. Creating demand: school health programmes
- 20. Creating demand: in the workplace
- 21. Creating demand: promotion & access
- 22. Equipment
- 23. Equipment
- 24. Equipment
- 25. Vision testing Priority age group: Children aged 12 – 14 years Each eye is tested: If vision <6/12 in either eye then refer
- 26. Vision testing School teachers can be trained to do an initial visual assessment Teachers are provided with: Vision kit Referra l protoco l Support
- 27. School vision testing programmes Recruit science teachers and teachers who wear spectacles Teachers must have support of school authorities
- 28. Vision testing in schools: Key points Teachers must be trained and supported Test each eye Children that fail the 6/12 visual acuity cut off must be referred, using an agreed method
- 29. School vision testing programmes Train teachers to refer each case they identify All testing and referral information should be recorded Children who are prescribed spectacles should also be followed up
- 30. School vision testing programmes Support and counselling must be provided to parents and children
- 31. Monitor school vision testing programmes in order to know: Coverage Uptake of referral Effectiveness of teacher training Acceptance of correction
- 32. Monitoring example 5,000 children enrolled 3,000 children vision tested
- 33. Coverage = 5,000 children enrolled 3,000 children vision tested 3,000 5,000 x 100 = 60%
- 34. Uptake = 110 children referred 75 children present 75 110 x 100 = 68%
- 35. Correct referrals = 75 children present 55 children referred 75 110 x 100 = 73%
- 36. Acceptance rate = 55 children referred 40 children accept correction 40 55 x 100 = 73%
- 37. Data can be monitored on a monthly basis and used to adjust the intervention
- 38. Vision testing in schools can have a huge impact
- 39. Services need to be planned with: Effective communic- ation Good monitoring and management Adequate resources
- 40. In conclusion Refractive error is the second most important cause of visual impairment and blindness globally Correction is relatively simple and the challenges are in access, affordability and acceptance
- 41. In conclusion Comprehensive service delivery at community level is essential School vision testing is an important strategy
- 42. Written by Dr Daksha Patel © 2016 International Centre for Eye Health, London School of Hygiene & Tropical Medicine. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license. Taken from the free online course: Global Blindness: Planning and Managing Eye Care Services. We encourage the use and adaptation of this resource for teaching and learning. Find more Open Educational Resources for eye care on our website at http://iceh.lshtm.ac.uk/oer
Editor's Notes
- Welcome to this presentation on managing refractive error. By the end of it you should be able to: Define refractive error and describe its epidemiology Explore considerations for service delivery at community level Appraise school health programmes and their management
- Refractive error in the public health context is defined as a presenting visual acuity of less than 6/18 which can be corrected by refraction or by pin hole - temporarily. Image: Fábio Franci CC BY-NC 2.0 https://flic.kr/p/9oypaq
- Correctable myopia is defined as worse than -1 dioptre. Correctable hyperopia is defined as +3 dioptres or more And it is essential to correct astigmatism of 1.5 dioptres or more
- The patient’s presenting visual acuity is categorised using the World Health Organisation’s International Classification of Disease.
- Uncorrected refractive error is the second major cause of blindness and low vision in the world, after cataract. Estimates from 2004, indicate that over 8 million people are blind and 145 million are visually impaired because they lack refractive correction.
- Who is most affected by refractive error? In children under 15 years, the prevalence of refractive error has been found to be higher in urban areas than in rural settings. This is possibly due to a direct cause and effect relationship between access to education and myopia. Image: NCVO London CC BY 2.0 flic.kr/p/e6frPR
- Refractive error amongst 94 million people over the age of 50 includes cataract related index myopia or even uncorrected aphakia. Image: John Tucker CC BY-NC-SA 2.0 flic.kr/p/4bSpXg
- The largest burden of refractive error is in India and China. More research is needed about how and where to identify and treat people with uncorrected refractive error. Some estimates for service coverage shows urban settings have better services, particularly for children.
- Why is there so much uncorrected refractive error? Many settings lack vision testing for children to ensure early detection and management. Lack of refractive services Limited affordability of spectacle correction, particularly in rural communities
- Sometimes, spectacles are not regarded as an essential medical intervention There may be cultural disincentives, which mean that people choose not to wear or accept correction - especially girls.
- Visual impairment from refractive error impacts individuals and society, leading to: Limited educational performance and success amongst children Social isolation and fewer opportunities for work and education
- More exposure to morbidities and higher mortality rates Lower quality of life and poverty
- There are two strategies for improving access to comprehensive community based eye care – static and outreach. Ideally, services are planned for a population of 50,000 and focus on increasing demand and supply.
- At a primary level, ophthalmic assistants or nurses can be trained to perform eye examinations and refraction. To minimise referrals, they can also be trained to dispense spectacles directly. Image: Aravind Eye Hospitals CC BY-NC 2.0 flic.kr/p/9w7mV8
- Estimating the demand for spectacles can be calculated from prevalence data for the target population or from similar settings.
- Where no data is available, 20% of the total population is a reasonable estimate. Understanding the demand allows planners and managers to appropriately allocate refraction and dispensing equipment and spectacles as well as numbers of trained personnel.
- Social marketing of refraction services has been a successful model in creating demand and raising awareness. This has been particularly successful in India through vision centres. Image: Graham Dyer CC BY-NC 2.0 flic.kr/p/dQouuo
- School health programmes, aimed particularly at the early teenage group, have also been shown to be effective. Image: Jenny Matthews/Sight Savers International CC BY-NC 2.0 flic.kr/p/9wBXTg
- Targeting younger, economically active, groups in the workplace or colleges is another option. Image: Christopher Congdon CC BY-NC 2.0 flic.kr/p/dsJMce
- In the over 50 age group, health promotion and access to services will also improve uptake. Image: Anita Shah CC BY-NC 2.0 flic.kr/p/9oSjUS
- Refraction equipment and spectacle dispensing equipment are both necessary to deliver comprehensive services. Image: Victoria M Sheffield CC BY-NC 2.0 flic.kr/p/9sda1W
- Additionally a range of frames and lenses suitable for local preferences must be stocked, particularly for children and girls. Image: Clare Gilbert CC BY-NC 2.0 flic.kr/p/dWuoGd
- Equipment and consumables are managed using an inventory and a reliable supply chain. Image: Jessica Echerri CC BY 2.0 bit.ly/1xavZBr
- The priority age group that needs vision testing at least once is children aged 12 to 14 years. This is to detect myopia of puberty. Younger age groups are tested if resources are available. Each eye is tested and vision less than 6/12 in either eye is defined as a case for referral and further testing. Lower cut off of less than 1 dioptre correction often results in poor adherence to spectacle wearing amongst children. Image: Elizabeth Kishiki CC BY-NC 2.0 flic.kr/p/bXgDET
- In some settings, school teachers can be trained to do an initial vision assessment within the school. Teachers are provided with a vision kit, referral protocol and support from local optometry services.
- In school vision testing programmes recruiting science teachers who can explain the benefits to parents are an ideal choice, as are teachers who wear spectacles as they will have an understanding and empathy for refractive error. The teachers must have the support of school authorities.
- The process of vision testing is made as simple as possible. Key points to remember are: Teachers must all be trained and supported Test each eye Children that fail the 6/12 visual acuity cut off must be referred, using an agreed method
- Train teachers to refer each case they identify. All the testing and referral information should be recorded for monitoring and evaluation Children who are prescribed spectacles should also be followed up between 3 to 6 months.
- Support and counselling should be provided to parents and children
- Management collect data to monitor school vision testing programmes in order to Know the coverage: this is the number of children whose vision has been tested by teachers Know the uptake of referral: how many of the referred children actually present to optometrists Establish how effective the teachers’ testing is. If there are too many false referrals, retraining of teachers may be necessary Understand the acceptance of refractive correction This is achieved by revisiting the school 3-6 months later and identifying which children are still using their spectacles.
- Let’s look at monitoring in more detail using an example. There are 5,000 children in the district schools aged 12 to 14 and 3,000 of them undergo vision testing:
- To calculate the coverage of services we divide 3,000 by 5,000 and multiply by 100 to get a percentage. This gives us a 60% coverage
- 110 children are referred for refraction and 75 present to the optometrist. To calculate the uptake of vision testing we divide 75 by 110 and multiply by 100. This gives us a 68% uptake of the service.
- 55 children out of 75 that presented are referred on to be prescribed spectacles. The percentage of correct referrals by teachers is calculated by dividing 55 by 75 and multiplying by 100. This gives us a 73% correct referral rate. This is good but it we should also establish why all the children did not come.
- 40 children are still wearing their spectacles 3 months later. To work out the acceptance rate we divide 40 by 55 and multiply by 100. This gives us a 73% acceptance rate.
- This data can be monitored on a monthly basis and used by management to adjust the intervention appropriately.
- Vision testing in schools is simple to conduct and can have a huge impact on children and their education. Image: London School of Hygiene & Tropical Medicine (Priya Morjaria) CC BY-NC 2.0
- Services need to be planned with adequate resources, good monitoring and management supported by effective communication between schools and optometry services.
- In conclusion: Refractive error is the second most important cause of visual impairment and blindness globally Correction is relatively simple and the challenges are in access, affordability and acceptance of spectacle correction.
- To meet the need, comprehensive service delivery at community level is essential. School vision testing is an important strategy to address refractive error needs in children and it can be done by trained and willing teachers.