IAPB Refractive Error Program Committee
The Elimination of
Vision Impairment from Uncorrected Refractive Error
Prepared by Brien Holden, Timothy Fricke, Kovin Naidoo, Hasan Minto, Gerhard Schlenther, Sonja Cronje, Phil Hoare, Hannah Faal
, Jerry Vincent
, Clare Gilbert, Anthea Burnett, David Wilson, Prakash Paudel and REPCom.
An initial draft, based on prior work of the Refractive Error Working Group, was presented by the International Centre for Eyecare Education to the February 2008 meeting of REPCom and IAPB Board of Trustees in Chittagong, Bangladesh
Refractive Error Program Committee Secretariat:
Refractive Error Program Committee Members:
Brien Holden (Chair), Kovin Naidoo, Hasan Minto, Hannah Faal, Clare Gilbert, Christian Garms, Gullapalli N Rao, Phil Hoare, Leon Ellwein, Earl Smith, Jerry Vincent, Babar Qureshi, Robert Chappell, Ivo Kocur, Ramachandran Pararajasegaram, Debbie Sweeney, Gerd Schlenther, Timothy Fricke
International Centre for Eyecare Education (ICEE)
TABLE OF CONTENTS
The road map to reducing refractive blindness and vision impairment 3
1 DEFINITIONS AND PROTOCOLS 5
1.1 Glossary of Terms 5
1.2 Definitions of Vision, Visual Acuity, Vision Impairment and Blindness 6
1.3 Cadres Involved in Refractive Care 7
1.4 Instrumentation, Techniques and Measurement Methods for Refractive Care 8
1.5 Standardized Treatment Guidelines 9
2 CONSOLIDATE AND UPDATE THE EVIDENCE BASE 11
2.1 Epidemiology 11
2.2 Health Economics 12
2.3 Quality of Life and Cost-Utility 13
2.4 Treatment Coverage 13
2.5 Techniques and Instruments 14
2.6 Best-Practice Models 15
3 SERVICE DELIVERY SYSTEMS AND CONSUMER DEMAND 17
3.1 Delivery of Refractive Care 17
3.2 Education and Advocacy 20
3.3 Health Promotion to Overcome Barriers 22
4 HUMAN RESOURCES 24
4.1 Personnel Development 24
4.2 Personnel Training 26
4.3 Challenges to Human Resource Development 27
5 INFRASTRUCTURE, TECHNOLOGY AND GLOBAL SUPPLY STRATEGIES 28
5.1 Refraction Service Requirements 28
5.2 Technology Guidelines 29
5.3 Global Supply Strategies 31
6 INTEGRATION OF REFRACTIVE SERVICES INTO MAINSTREAM HEALTH CARE 32
ANNEX 1 Visual Acuity Conversion Table 35
ANNEX 2 Treatment Guideline Decision Pathways 36
ANNEX 3 Quality of Life and Cost Utility Background 39
ANNEX 4 Comparison of Eye Care Service Delivery Models/ Approaches 41
ANNEX 5 Vision Centres 42
ANNEX 6 Costs of Refractive Care Setup 46
ANNEX 7 Durban Declaration 48
ANNEX 8 References 50
The Refractive Error Program Committee (REPCom) of the International Agency for the Prevention of Blindness (IAPB) has produced this Strategy to assist any government, public health system, private health system, research institute, non-government organization, health practitioner, lay-person or community who seeks to reduce blindness and vision impairment caused by Uncorrected Refractive Error (URE).
URE is the largest global cause of vision impairment. URE was estimated to impair the distance vision of 153 million people in 2004 (8 million of these people were blind).2 These figures do not include any estimate of near vision impairment. Any type of refractive error, depending on magnitude and other factors, can affect near vision. Presbyopia specifically affects near vision. Uncorrected presbyopia was estimated to impair the near vision of 517 million people in 2005.3
URE may result in lost education and employment opportunities, lower productivity and impaired quality of life.1, 4, 5 As such, refractive care is an integral component of health systems and poverty alleviation efforts.
A meaningful solution involves more than the distribution of 670 million pairs of spectacles. Assessment of individuals who have refractive errors, particularly those aged 45 years or over, provides an opportunity to identify other potentially blinding conditions (such as glaucoma and diabetic retinopathy) before they cause permanent vision loss. Public, private, social entrepreneurship and other models for delivering refractive services all have a role in contributing to empowerment of local communities and sustainability of primary eye care services.
REPCom views the following areas as pivotal to the global effort to eliminate refractive error blindness and vision impairment:
Definitions and Protocols. Global blindness prevention efforts benefit from using internationally agreed definitions and protocols to guide service delivery and education in areas relevant to the alleviation of refractive blindness and vision impairment.
Consolidating and Updating the Evidence Base. Overcoming gaps in refractive error knowledge and monitoring progress by prioritizing the following areas:
Epidemiology (including distance and near vision impairment due to uncorrected refractive error);
Economics (including the economic burden of URE and the cost-effectiveness of interventions);
Quality of Life and cost-utility (including identification or development of appropriate tools, and measurement of the impact of refractive correction);
Coverage (including services and spectacles);
Techniques and instruments (including VA charts, low-cost auto-refractors, and blur function), and
Best-practice models (identification of them via measures of efficiency and efficacy, analysis of what makes them good, how to generalize them and replicate their success in other regions).
Service Delivery Systems and Consumer Demand. Defining strategies for the global elimination of refractive error blindness and vision impairment via:
Effective screening and refraction examinations;
Availability of affordable spectacle correction for individuals who have refractive error blindness or vision impairment;
Visual health promotion to build individual and community awareness about refractive error, the benefits of correction and the availability of services;
Detection and appropriate referral of individuals who have eye or vision problems beyond the scope of the provider’s training, with particular emphasis on conditions prioritized by local eye care plans; and
Eye health promotion that achieves community education (aimed at engaging individuals, families and communities who have uncorrected refractive error), service improvements (aimed at practitioners to enable increased quality and quantity of services), and advocacy (aimed at funders and legislators who can facilitate growth of services).
Human Resources. Recommendations for training needs and competencies of the cadres who will do the work of eliminating refractive error blindness and vision impairment.
Infrastructure, Technology and Global Supply Strategies. Requirements, suggestions and guidelines in the following areas:
Refraction service requirements at primary, secondary and tertiary levels;
Technology for refractive devices, spectacles, and optical dispensing laboratories;
Enable NGOs and governments to organize efficient and cost-effective manufacture, delivery and supply of services and spectacles to people and areas carrying the largest burden of refractive error blindness and vision impairment.
Integration of Refractive Services into National Blindness Prevention Plans. Identifying strategies for integrating refractive services into national and regional plans, ways to develop and share the tools needed to eliminate refractive error vision impairment, and identify potential vehicles for implementation.
1 DEFINITIONS AND PROTOCOLS
1.1 Glossary of Terms
AMD Age-related Macular Degeneration
APEDS Andhra Pradesh Eye Disease Study
BMES Blue Mountains Eye Study
CBMI Christian Blind Mission International
DALY Disability Adjusted Life Year
DCEC District Comprehensive Eye Care
ETDRS Early Treatment of Diabetic Retinopathy Study
GRC Global Resource Centre
HR QoL Health Related Quality of Life
IAPB International Agency for the Prevention of Blindness
ICEE International Centre for Eyecare Education
IVI Impact of Visual Impairment
KAP Knowledge Attitude Practice
logMAR logarithm of Minimum Angle of Resolution (a unit for specifying VA)
LVPEI LV Prasad Eye Institute
MLOP Mid-Level Ophthalmic Personnel
NGO Non-Government Organisation
NVR QoL Near Vision Related Quality of Life
QALY Quality Adjusted Life Year
QoL Quality of Life
RMS Ready-Made Spectacles
SSI Sight Savers International
NEI National Eye Institute (of the National Institutes of Health, USA)
RAAB Rapid Assessment of Avoidable Blindness
REPCom Refractive Error Program Committee
RESC Refractive Error Studies in Children
URE Uncorrected Refractive Error
VA Visual Acuity
VC Vision Centre
VFQ Visual Function Questionnaire
VI Vision Impairment
VOSH Volunteer Optometric Services to Humanity
WCO World Council of Optometry
WHO World Health Organization
1.2 Definitions of Vision, Visual Acuity, Vision Impairment and Blindness
The ongoing process of terminology standardization has lead to some inconsistencies between published literature and governing bodies such as the WHO. As at August 2008, the following definitions are recommended. They are based on World Health Organization policy, published evidence, REPCom consensus, or a combination of these where conflicting definitions exist. They highlight or expand on previously published definitions directly relevant to refractive care. It is noteworthy that future developments may include linking functional status to visual acuity (VA).
Unaided Vision: VA without optical correction.6
Presenting Vision: VA with habitual optical correction.2, 7
(For a person who does not use spectacles, presenting and uncorrected VAs are always the same)
Best-corrected VA: VA with optimal spectacle correction in place.2
Moderate Vision Impairment: Presenting vision worse than 6/18 but equal to or better than 6/60 in the better eye.2, 8
Severe Vision Impairment: Presenting vision worse than 6/60 but equal to or better than 3/60 in the better eye.2, 8
Blindness: Presenting vision worse than 3/60 in the better eye.2, 7-9
Visioni Impairment (VI): Presenting vision worse than 6/18 in the better eye.2, 8, 9
(Additionally, a consensus of the Refractive Error Working Group of the World Health Organization (informal meeting in Geneva, 3 – 5 July 2000) suggested lowering the cutoff to 6/12 in the better eye for children younger than 16 years of age)1
Low Vision: VA worse than 6/18 but better than or equal to light perception in the better eye, or a binocular visual field of less than 10 degree from the point of fixation after standard treatments (including best available optical correction).7, 8, 10
(Low Vision implies VI even after management of any treatable conditions (e.g. correction of refractive error, or cataract surgery), but that the person has potential to use vision for planning and/or execution of a task)
Blindness at near: Presenting vision at the individual’s required working distance that is worse than N64 in the better eye (this print size held at 40cm provides the same angular subtense as distance VA of 3/60. (REPCom consensus)
(A future change could be driven by research advocated in Section 2.5 – changing to a near acuity corresponding to a basic functional need such as ability to identify faces)
Vision impairment at near: Presenting vision at the individual’s required working distance worse than N8 in the better eye. (REPCom consensus)
(REPCom suggests object size at preferred working distance as a more logical definition than angular subtense at a set 40cm for near. Furthermore, N8 is a common newspaper print size across the world, which although only equivalent to 0.4 (6/15) rather than 0.5 logMAR (6/18) when held at 40cm, makes it a more practical choice. This is also consistent with a report that quality of life is more sensitive to near VI than distance VI.11)
Some countries have different cutoff values (e.g. blindness defined around 6/60 rather than 3/60), which exist for scientific, historical, legal and/or social reasons. We do not advocate changing regional, national or local definitions. However we do advocate collection of both data types so that global patterns can be observed. For example, a blindness prevalence study could find that “Country-defined blindness prevalence was x%, while WHO-defined blindness prevalence was y%”.
Given variations in units used to define VA in different jurisdictions, a conversion table is provided in Annex 1.
It should also be noted that vision impairment and blindness definitions are not necessarily advocated as cutoffs that determine spectacle wear versus non-spectacle wear. Ideally there would be an objective measure of the impact of URE on broad visual function (the sum of the effect on a variety of tasks which combine to describe the overall effect of URE on an individual’s life in a way that a simple VA measure does not). Since this ideal functional vision impairment measure does not exist, vision impairment and blindness cutoffs are the best available way to estimate the epidemiology of the more severe effects of URE. Vision impairment cutoff could be used as a guide for prescribing spectacles in places of limited resources. In contrast, patient/client choice should be the deciding factor in user-pays systems. A variety of compromises can be applied in adequately resourced, subsidized systems. Treatment Guidelines are provided in Section 1.5.
1.3 Cadres Involved in Refractive Care
A variety of cadres provide refractive care across jurisdictions, and often there is a cross-over of responsibility within jurisdictions. It is worth noting that although conflict exists between some cadres in some jurisdictions, the magnitude of the problem of URE means that there is more refractive care required in the world than can be provided by all current carers put together. The following provides a basic definition of some cadres providing refractive care.
Optometrists have a range of responsibilities in different jurisdictions, although refraction and detection of eye disease is common to all. Optometrists are usually university trained for 4 or more years, and work in public, private and NGO settings. Associated ophthalmic dispensers or spectacle technicians often supply spectacles after an optometrist has refracted a patient/client.
Ophthalmologists can theoretically refract in all jurisdictions, although their workload of other eye care duties means that in practice refractive care is more commonly provided by associated MLOP.
Mid-Level Ophthalmic Personnel including vision technicians, ophthalmic assistants, orthoptists, ophthalmic nurses and others most commonly provide refractive care in association with an ophthalmologist, but work independently in some jurisdictions. They sometimes provide complete refractive care (refraction and spectacle dispensing), but often only refract and provide an optical prescription which a patient/client must fill at a private optician to complete their refractive care.
Opticians refract in some jurisdictions, but more commonly supply spectacles made to an optical prescription supplied by a client from an optometrist, an ophthalmologist or MLOP. Opticians usually work in for-profit situations.
Ophthalmic dispensers and spectacle technicians are responsible for a variety of tasks centered on constructing and dispensing spectacles. Training is usually done on-the-job and/or short-course.
Governments should give due consideration to appropriate registration of cadres involved in refractive care. Government health care systems should make appropriate use of each of the available cadres.
1.4 Instrumentation, Techniques and Measurement Methods for Refractive Care
The following provides a general guide to the instrumentation, techniques and measurement methods of refractive services. It is not meant as a complete guide to all possibilities or to provide textbook level of detail.
VA charts (for both distance and near assessment) should have logMAR or ETDRS format.8 The difference between successive lines on a chart of this format is equivalent regardless of position on the chart – a requirement for the Standardized Treatment Guidelines provided in Section 1.3.
Appropriate optotypes should be available. Snellen Letters of the Latin alphabet are not adequate where a different alphabet is used, pre-literate children are to be assessed, or there is significant non-literacy in the community. The aims for alternative optotypes should include testability with the population to be assessed, equal visibility of the symbols used, adaptability to verbal and non-verbal (e.g. pointing) responses, and published validation research.
Examples of non-Snellen optotypes include Arabic numbers, Lea Symbols (sometimes called LH Symbols, designed by Lea Hyvärinen), Landolt C’s and Tumbling E’s
HOTV charts have also been validated as a matching task that works for pre-literate children12
Lea Symbols have superior testability in under 5 year olds13, 14
Differential visibility of the Tumbling E’s vertical options (up or down) compared to its horizontal options (left or right) effectively makes it a 2 alternative forced choice task at threshold (rather than 4 alternative for Lea Symbols or HOTV tasks), however validity appears uncompromised for adult patients15
Tumbling E’s are generally regarded as the most recognised non-literate VA task in the world and gain some level of testability from this
Printed charts are adequate, but should:
Have at least 80% contrast between the black letters and the white background8
Avoid edge-of-character pixilation
Avoid surface reflections
Be adequately illuminated (between 80 and 160 cd/m2, or standard indoor illumination)8
Distance VA should be measured three times; first with Both Eyes, then with the Right Eye (with the left eye adequately occluded), then with the Left Eye (with the right eye adequately occluded).
Adequate occlusion means using the palm of the patient’s hand rested gently on bones surrounding the eye on all sides, or a blank card of sufficient size, or an effective custom-made occluder. It does not include winking, resting fingers against a closed eye, or holding fingers in front of the eye to be occluded.
A comparison of refractive techniques is provided in Section 5.1.
Cadres performing refractions should be able to reliably perform at least one objective refraction technique (e.g. retinoscopy, autorefraction), and have access to necessary equipment (e.g. retinoscope, trial lens set and trial frame, or autorefractor).
Ability to perform reliable subjective refractions is also important.
Ability to determine near addition for correction of presbyopia (via near retinoscopy, subjective response or another reliable method) is essential.
1.5 Standardized Treatment Guidelines
Wherever resources permit, refractive care should be provided on an individual needs basis. Some individuals have high acuity needs and will be profoundly impaired in their activities of daily living by small amounts of URE. Other individuals have little or no need for fine visual acuity tasks and cope well with large amounts of URE. However, where resources are limited it is useful to objectively prioritize the people most in need of refractive care. The following Indications for Correction provide a way to objectively prioritize refractive care in situations of limited resources, but should not override individual needs where resources permit.
Indications for Correction are based on vision and VI definitions in Section 1.1. Treatment Guidelines are based on a combination of symptoms, the magnitude of refractive error, presenting distance & near vision, best-corrected distance & near vision, & other related ophthalmic factors. Decision pathways for the following Treatment Guideline descriptions are provided in Annex 2:
Correction for myopia is indicated if an appropriate refractive technique (e.g. retinoscopy) indicates significant myopia*, PLUS one or more of the following:
A patient reports difficulty with distance vision,ii
Minus powered lenses improve vision by 2 logMAR VA lines or more.
* The Refractive Error Working Group of the World Health Organization (informal meeting in Geneva, 3 – 5 July 2000) suggested “significant myopia” was -0.50DS or more for children, or -1.00DS or more for adults.1 Alternatively, any amount of myopia combined with BOTH dot points could also be considered an indication for correction.
Correction for hypermetropia is indicated if an appropriate refractive technique (e.g. retinoscopy) indicates significant hypermetropia**, PLUS one or more of the following:
A patient reports difficulty with (far or near) vision, discomfort with concentrated visual effort, and/or an esotropia,ii
Plus powered lenses improve vision by 2 logMAR VA lines or more, and/or noticeably improve comfort,
There is amblyopia (and the patient’s age suggests the amblyopia is potentially treatable), or esotropia or large esophoria (and the patient has some potential for normal binocularity).
** The Refractive Error Working Group of the World Health Organization (informal meeting in Geneva, 3 – 5 July 2000) suggested “significant hypermetropia” was +2.00DS or more at any age.1 Alternatively, any amount of hypermetropia combined with TWO OR MORE dot points could also be considered an indication for correction.
Correction for astigmatism is indicated if an appropriate refractive technique (e.g. retinoscopy) indicates significant astigmatism***, PLUS one or more of the following:
A patient reports difficulty with vision, and/or discomfort,ii
Cylindrical lenses improve vision by 2 logMAR VA lines or more, and/or noticeably improve comfort,
There is a suggestion of amblyopia (and the patient’s age suggests the amblyopia is potentially treatable).
*** The Refractive Error Working Group of the World Health Organization (informal meeting in Geneva, 3 – 5 July 2000) suggested “significant astigmatism” was more than 0.75DC.1 Alternatively, any amount of astigmatism combined with TWO OR MORE dot points is also an indication for correction.