8.2.2. Visual impairment and blindness

 

8.2.2.1. Introduction

 

Blindness has profound human and socioeconomic consequences in all societies. The costs of lost productivity and of rehabilitation and education of the blind constitute a significant economic burden for the individual, the family and society. A major cause of low vision and blindness is represented by uncorrected refractive errors. Refractive errors can be easily diagnosed, measured and corrected with spectacles or other refractive corrections to attain normal vision. However, various factors are responsible for refractive errors remaining uncorrected: lack of awareness and recognition of the problem at personal and family level, as well as at community and public health level; non-availability of and/or inability to afford refractive services for testing; insufficient provision of affordable corrective lenses; and cultural disincentives to compliance.

The economic effects of visual impairment can be divided into direct and indirect costs. The direct costs are those of the treatment of eye diseases, including the relevant proportions of costs for running medical and allied health services, pharmaceuticals, research and administration. The indirect costs include lost earnings of visually impaired people and their caregivers and costs for visual aids, equipment, home modifications, rehabilitation, welfare payments, lost taxation revenue and the impaired quality of life, pain, suffering and premature death that can result from visual impairment.

 

8.2.2.2. Data Sources

 

The first estimate of the global data on blindness was published in 1995 (Thylefors et al, 1995). Since the publication of the Global Data on Blindness in 1995, several population-based studies on the prevalence of blindness and visual impairment have been carried out. Surveys are available for a number of EU Member States, Acceding and EFTA Countries. The 2002 Global update of available data on visual impairment (Pascolini et al, 2004) is an important source of data. Data on childhood blindness are available from the report of a 1999 WHO scientific meeting (WHO, 2000), as well as from a comprehensive review of available data (Gilbert et al, 1999). A summary list of studies, with their basic features and results is available at http://www.who.int/blindness/publications/global_data.pdf. Self-reported data on sight problems have been also collected in several EU Member States by means of EU Labour Force Survey (LFS) carried out in 2002 and the EU SILC carried out in 2004. The results obstained with these two surveys have been analysed in a Report published in 2007 (APPLICA et al, 2007).

 

Definitions

 

Visual impairment includes low vision as well as blindness. Low vision is defined as visual acuity of less than 6/18, but equal to or better than 3/60, or a corresponding visual field loss to less than 20 degrees in the better eye with best possible correction (ICD-10 visual impairment categories 1 and 2). It should be noted that in the revision of the ICD-10 categories of visual impairment proposed in 2003 by a WHO consultation on the development of standards for characterization of vision loss, low vision is replaced by two categories: moderate visual impairment (presenting visual acuity less than 6/18 but equal to or better than 6/60) and severe visual impairment (presenting visual acuity less than 6/60 but equal to or better than 3/60) (WHO, 2003). Blindness is defined as visual acuity of less than 3/60, or a corresponding visual field loss to less than 10 degrees in the better eye with best possible correction (ICD-10 visual impairment categories 3, 4 and 5).

 

The definition of visual impairment in the International statistical classification of diseases, injuries and causes of death, 10th revision (ICD-10), H54, is based on “best-corrected” vision, i.e. visual acuity obtained with the best possible refractive correction. Presenting vision, i.e. visual activity obtained with current refractive correction, if any, as opposed to best-corrected vision, has been used to characterize visual impairment faced by people in daily activities.

Visual impairment caused by uncorrected or inadequately corrected refractive errors is defined as visual acuity of less that 6/18 in the better eye, which could be improved to equal or better than 6/18 by refraction or pinhole.

 

Prevalence of blindness and low vision

 

A review and selection, based on predefined criteria, of survey of visual impairment, was carried out by Resnikoff et al (2004). Prevalence of blindness in EUGLOREH countries, was estimated with the application of a number of assumptions to the data of surveys carried out in a limited number of countries in this area (Denmark, Finland, Ireland, Italy, Netherlands, United Kingdom, Bulgaria, Turkey, Iceland) (Resnikoff et al, 2004). Estimates for Bulgaria and Turkey were different from other EU Member States and Candidate Countries (Table 8.2) due to different assumptions applied to Country groups characterized mainly by different mortality levels (details on the classification of countries into subregions by WHO are reported in Murray et al, 2001).

 

Table 8.2. Prevalence of blindness and low vision, by WHO subregion, 2002

 

Although blindness in children remain a significant problem, affecting about 21000 children in EUR-A and EUR-C epidemiological region, about 76% of blind people in these countries and 75% in EUR-B1 epidemiological region are aged 50 or more. Based on the results of the available surveys, women seem more likely than men to suffer from visual impairment. An estimation of the visual impairment due to uncorrected or inadequately corrected refractive errors has also been carried out (Resnikoff et al, 2008) with two population-based surveys representative of the sampled areas, which were in Ireland (Donnelly et al, 2005) and Italy (Nucci et al, 2005). The results indicate a total prevalence of 2.0%, with 1.0% for people aged 5 to 39, 1.6% for people aged 40-49 and 3.6% for people aged 50 or more.

 

The analysis of the causes of blindness indicate that the leading cause of blindness is age-related macular degeneration in EUR-A countries, and cataract in EUR-B countries (Table 8.3). Glaucoma and diabetic retinopathy are also significant causes of blindness in all these countries. Age-related macular degeneration is an increasing cause of blindness, as could be expected by the increasing number of elderly people in developed countries.

 

Table 8.3. Causes of blindness as a percentage of total blindness – by WHO subregion, 2002

 

 

 

8.2.2.3. Data Description

 

A review and selection, based on predefined criteria, of survey of visual impairment, was carried out by Resnikoff et al (2004). Prevalence of blindness in EUGLOREH countries, was estimated with the application of a number of assumptions to the data of surveys carried out in a limited number of countries in this area (Denmark, Finland, Ireland, Italy, Netherlands, United Kingdom, Bulgaria, Turkey, Iceland) (Resnikoff et al, 2004). Estimates for Bulgaria and Turkey were different from other EU Member States and Candidate Countries (Table 8.2) due to different assumptions applied to Country groups characterized mainly by different mortality levels (details on the classification of countries into subregions by WHO are reported in Murray et al, 2001).

 

Table 8.2. Prevalence of blindness and low vision, by WHO subregion, 2002

 

Although blindness in children remain a significant problem, affecting about 21000 children in EUR-A and EUR-C epidemiological region, about 76% of blind people in these countries and 75% in EUR-B1 epidemiological region are aged 50 or more. Based on the results of the available surveys, women seem more likely than men to suffer from visual impairment. An estimation of the visual impairment due to uncorrected or inadequately corrected refractive errors has also been carried out (Resnikoff et al, 2008) with two population-based surveys representative of the sampled areas, which were in Ireland (Donnelly et al, 2005) and Italy (Nucci et al, 2005). The results indicate a total prevalence of 2.0%, with 1.0% for people aged 5 to 39, 1.6% for people aged 40-49 and 3.6% for people aged 50 or more.

 

The analysis of the causes of blindness indicate that the leading cause of blindness is age-related macular degeneration in EUR-A countries, and cataract in EUR-B countries (Table 8.3). Glaucoma and diabetic retinopathy are also significant causes of blindness in all these countries. Age-related macular degeneration is an increasing cause of blindness, as could be expected by the increasing number of elderly people in developed countries.

 

Table 8.3. Causes of blindness as a percentage of total blindness – by WHO subregion, 2002

 

8.2.2.4. Future developments

 

Periodic surveys are important for monitoring the occurrence and preventing avoidable causes of visual impairment, including inadequately corrected refractive errors. Disaggregated data need to be collected in population groups characterised by different socio-economic conditions, for ensuring greater equity in service provision. It is important that screening of children for refractive errors are carried out at community level and integrated into school health programmes; the need should be assessed for education and awareness campaigns aiming at ensuring that corrections are used and cultural barriers to compliance are addressed and removed. It is also important that corrections are let affordable for people of all ages, and in particular for the elderly. Training of ophthalmologists in latest techniques to perform surgeries and provide up-to-date care has been suggested as a need in some EU new Member States (Kocur, 2004)

 

8.2.2.5. Control tools and policies

 

The global initiative known as ‘VISION 2020: the Right to Sight’ is an established partnership between the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB). It was launched in 1999 with the twin aims of eliminating avoidable blindness by the year 2020 and preventing the projected doubling of avoidable visual impairment between 1990 and 2020. The ultimate goal of the initiative is to integrate a sustainable, comprehensive, high-quality, equitable eyecare system into strengthened national health-care systems. In May 2006, the World Health Assembly adopted Resolution WHA 59.25, ‘Prevention of avoidable blindness and visual impairment’, which expanded on the base laid down in an earlier resolution (WHA 56.26) and created a global mandate for VISION 2020. The document “GLOBAL INITIATIVE FOR THE ELIMINATION OF AVOIDABLE BLINDNESS - ACTION PLAN 2006–2011” highlights the main issues and developments and lays out a clear agenda for the next phase of implementation of VISION 2020 (WHO, 2007).

The three core approaches of VISION 2020 to the prevention of blindness and visual impairment remain disease control, human resource development, and infrastructure and technology. Although these approaches are defi ned as three distinct components, their interdependence is obvious: disease control and elimination require an adequately trained, functional workforce with an enabling infrastructure and technology. The prevention of avoidable visual impairment will be achieved only if effective, efficient, comprehensive eye health-care services are integrated into well managed, well-monitored national health systems.

 

To accelerate implementation of VISION 2020, some EUGLOREH countries together with other countries in each WHO region were selected for intensified assistance, and the list of countries was submitted to the World Health Assembly in 2006.

 

8.2.2.6. References

 

Donnelly UM, Stewart NM and Hollinger M. (2005): Prevalence and outcomes of childhood visual disorders. Ophtalmic Epidemiology 12:243-250.

European Union Statistics on Income and Living Conditions (EU-SILC) (2007): Men and women with disabilities in the eu: statistical analysis of the LFS ad hoc module and the EU-SILC. On line publication available at: http://ec.europa.eu/employment_social/index/lfs_silc_analysis_on_disabilities_en.pdf

Gilbert CE, Anderton L, Dandona L, Foster A. (1999): Prevalence of visual impairment in children: a review of available data. Ophthalmic Epidemiology 6:73-82.

Kocur I (2004): Fifteen years of eye health care service transition in Eastern Europe. IAPB Newsletter 41:3-4 (on-line document available at: http://www.iapb.org/newsletters/41_IAPB_news-jan04.pdf )

Murray CJL, Lopez AD, Mathers CD, Stein C (2001): The Global Burden of Disease 2000 project: aims, methods and data sources. (Global Programme on Evidence for Health Policy Discussion Paper No. 36). Available at: http://www.who.int/healthinfo/boddocs/en/index.html.

Nucci C, Cedrone C, Culasso F, Ricci F, Cesareo M, Corsi A and Cerulli L. (2005): Incidence of visual loss in the Ponza Eye Study, Italy. Eye 19:175-82

Pascolini D, Mariotti S, Pokharel GP, Pararajasegaram R, Etya’ale D, Négrel A-D, et al. (2004): 2002 Global update of available data on visual impairment: a compilation of population-based prevalence studies. Ophthalmic Epidemiology 11:67-115.

Resnikoff S, Pascolini D, Etya’ale D, Kocur I, Pararajasegaram R, Pokharel GP and Mariotti SP (2004): Global data on visual impairment in the year 2002. Bulletin of the World Health Organization 82:844-851

Resnikoff S, Pascolini D, Mariotti SP and Pokharel GP (2008): Global magnitude of visual impairment caused by uncorrected refractive errors in 2004 Bulletin of the World Health Organization 86:63–70.

Thylefors B, Négrel A-D, Pararajasegaram R, Dadzie KY. Global data on blindness. Bulletin of the World Health Organization. 1995;73(1):115-21.

WHO (2000): Preventing blindness in children. Report of a WHO/IAPB scientific meeting Hyderabad, India 1999. Geneva: WHO; WHO document WHO/PBL/00.77.

WHO (2003): Prevention of blindness and deafness. Consultation on development of standards for characterization of vision loss and visual functioning. Geneva 4-5 September 2003. Document WHO/PBL/03.91

WHO (2007): Global initiative for the elimination of avoidable blindness, action plan 2006 - 2011. Available online at: http://www.who.int/blindness/Vision2020%20-report.pdf