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Biomedical subjects

A D Négrel

Publications and source records attributed to A D Négrel.

At least 19 recordsLinked to original sources
PubMed2004

2002 global update of available data on visual impairment: a compilation of population-based prevalence studies.

PURPOSE: For the past 25 years, the WHO Programme for the Prevention of Blindness and Deafness has maintained a Global Data Bank on visual impairment with the purpose of storing the available epidemiological data on blindness and low vision. The Data Bank has now been updated to include studies conducted since the last update in 1994. METHODS: An extensive literature search was conducted in international and national scientific and medical journals to identify epidemiological studies that fulfilled basic criteria for inclusion in the Data Bank, namely a clearly stated definition of blindness and low vision, and prevalence rates derived from population-based surveys. Sources such as National Prevention of Blindness Programmes, academic institutions or WHO country or regional reports were also investigated. RESULTS: Two-hundred-and-eight population-based studies on visual impairment for 68 countries are reported in detail, providing an up-to-date, comprehensive compilation of the available information on visual impairment and its causes globally.

Adolescent↗
PubMed1998

The global impact of eye injuries.

Using data compiled from the ophthalmic literature and WHO's Blindness Data Bank, the available information on eye injuries from an epidemiological and public health perspective has been extensively reviewed. This collection of data has allowed an analysis of risk factors, incidence, prevalence, and impact of eye injuries in terms of visual outcome. However, most of the estimates are based on information from More Developed Countries (MDCs). The severity of eye injuries can be assessed through proxy indicators such as: (i) potentially blinding bilateral injuries; (ii) open-globe injuries; (iii) endophthalmitis; (iv) enucleation or (v) defined visual impairment. Major risk factors for ocular injuries include age, gender, socioeconomic status and lifestyle. The site where the injury occurs is also related to a risk situation. Available information indicates a very significant impact of eye injuries in terms of medical care, needs for vocational rehabilitation and great socioeconomic costs. The global pattern of eye injuries and their consequences emerging from the present review, undertaken for planning purposes in the WHO Programme for the Prevention of Blindness, suggests that: some 55 million eye injuries restricting activities more than one day occur each year; 750,000 cases will require hospitalization each year, including some 200,000 open-globe injuries; there are approximately 1.6 million blind from injuries, an additional 2.3 million people with bilateral low vision from this cause, and almost 19 million with unilateral blindness or low vision. Further epidemiological studies are needed to permit more accurate planning of prevention and management measures; a standardized international template for reporting on eye injuries might be useful to this effect, along the lines of the reporting occurring through the US Eye Injury Registry.

Adolescent↗
PubMed1997

[World Health Organization alliance for the elimination of trachoma].

Although trachoma has either decreased or disappeared in many Third World countries through socio economic development during the past forty years, it remains a major problem among the poorest communities, which is often ignored by decision-makers when setting priorities. Fortunately, recent developments will allow to overcome many of the past obstacles and to offer new opportunities for trachoma control programmes. WHO aware of this new favourable context for trachoma control has taken the leadership in mobilizing and coordinating trachoma control efforts through the creation of a WHO Alliance for the Global Elimination of Trachoma. The aim of this Alliance is to assist Member States where trachoma is endemic achieve the goal of (global) elimination of trachoma by the year 2020. This is indeed possible through the combination of various interventions such as those proposed by the SAFE strategy (Surgery for trichiasis, Antibiotics, Face washing and Environmental changes) recommended by WHO. The prevention of trachoma and its treatment will rely largely on the efforts made by the endemic countries concerned with this problem. Therefore, new and or existing trachoma control programmes should be either implemented or strengthened at community-based level within the framework of the available primary health care systems based on the application of the SAFE strategy and on the assistance of the Alliance partners.

Anti-Bacterial Agents↗
PubMed1995

[Blindness in Benin].

A population-based survey of the prevalence and cause of blindness and poor vision was conducted in the Republic of Benin in 1990 using a stratified cluster random sampling procedure. The survey was designed and implemented through the collaboration of the Ministry of Health of the Republic of Benin and the Programme for the Prevention of Blindness of the World Health Organization (WHO/PBL). Survey data were analyzed at the International Centre for Eye Health, Institute of Ophthalmology, University of London, United Kingdom. In accordance with the procedures recommended by WHO/PBL, 7272 individuals were recruited and 7047 were examined. The survey achieved excellent coverage in all locations with an overall coverage of 96.9%. The prevalence of blindness (visual acuity less than 3/60 in the better eye) was 0.6% (CI95% = 0.4%-0.9%). The prevalence of poor vision (best vision less than 6/60 but not blind in the better eye) was estimated at 2.6% (CI95% = 2.1%-3.1%). The major causes of blindness were age-related cataract and glaucoma (54% and 15% respectively of blind people recruited). The major cause of poor vision were cataract, refractive errors, and macular disorders (64%, 9.6%, and 9.0% respectively of people recruited with poor vision. The survey results indicate that there is an urgent need for basic eye care services. Cataract has been designated as a priority target in the recently designed National Blindness Prevention Programme now being implemented in the Republic of Benin. With proper management of this problem, the current prevalence of blindness and poor vision could be reduced by at least 45%. At the end of this cluster study, the design effect (D = 1.56) and rate of homogeneity (ROH = 0.002) were computed for an average number of 250 people per cluster.

Adolescent↗
PubMed1995

[Cataract-related blindness in Morocco. The Moroccan Group of Epidemiologic Evaluation of Blindness].

The lack of sound and recent epidemiological data on the prevalence and causes of blindness has hampered the development and evaluation of the Moroccan Programme for the Prevention of Blindness. For this reason a population-based survey using a stratified (urban/rural) sampling design for random selection of clusters was carried out in the Kingdom of Morocco from May 15 until June 30, 1992. The procedures used for this survey were those proposed by the WHO Programme for the Prevention of Blindness. A total of 10,198 people were recruited and 8878 examined for a participation rate of 87%. The size and representativity of the sample satisfactorily guaranteed the order of magnitude and accuracy of eye health indicators used by health planners. The crude point prevalence of blindness was 0.8%, that of bilateral poor vision was 2.3%, and that of unilateral poor vision was estimated to be 2.8%. Based on these findings 195,000 people would be blind and 1,300,000 would be at risk of becoming so, for a total of approximately 1,500,000 people with serious visual impairment. Age-related cataract was the most important cause of blindness (45.5%) and bilateral poor vision (43.1%). The prevalence of cataract-related visual impairment--operable or inoperable--was estimated to be 2.1% of the survey sample. Applying a realistic algorithm to the survey data, it was estimated that the backlog for cataract surgery in Morocco in 1992 was in the order of 502,000 eyes in approximately 287,000 people. The percentage of patients who had undergone cataract surgery in hospital was 0.8%. Posterior lens dislocation according to the traditional "couching" method was noted in 0.1% of people studied. It was estimated that 25% of the demand for cataract surgery was covered by available facilities and that 40% of people with aphakia could not obtain eye care.

Adolescent↗
PubMed1995

Global data on blindness.

Globally, it is estimated that there are 38 million persons who are blind. Moreover, a further 110 million people have low vision and are at great risk of becoming blind. The main causes of blindness and low vision are cataract, trachoma, glaucoma, onchocerciasis, and xerophthalmia; however, insufficient data on blindness from causes such as diabetic retinopathy and age-related macular degeneration preclude specific estimations of their global prevalence. The age-specific prevalences of the major causes of blindness that are related to age indicate that the trend will be for an increase in such blindness over the decades to come, unless energetic efforts are made to tackle these problems. More data collected through standardized methodologies, using internationally accepted (ICD-10) definitions, are needed. Data on the incidence of blindness due to common causes would be useful for calculating future trends more precisely.

Blindness↗
PubMed1994

The global impact of glaucoma.

Although glaucoma is a major global cause of blindness, the lack of a uniform definition of the disease in its different forms makes it difficult to assess its public health impact. By considering the common features of glaucoma, we have analysed available data on the three main forms of the disease: congenital/hereditary glaucoma, primary open-angle, and primary angle-closure glaucoma. A simple model was then developed to estimate the extent of glaucoma on a regional basis, taking into account demographic data, e.g., age distribution, gender and ethnic groups. Overall, the results demonstrate that glaucoma is responsible for approximately 5.2 million blind (15% of the total burden of world blindness).

Adult↗
PubMed1994

Developments for a global approach to trachoma control.

Because of the life-style/environment-related determinants of the disease, trachoma control activities should be multisectorial and multidisciplinary in order to be effective and long lasting. Medical and epidemiological components to be included in the global approach have largely benefited by the existence of the simplified trachoma grading system. In other respects, long-term outcomes of trichiasis surgery are better evaluated and various surgical procedures are available. On the other hand, despite the knowledge that community participation is one of the essentials of trachoma control activities, this element all too often remains neglected. Therefore, realistic and practical community approaches need to be specified which are suited to various socio-cultural settings. Thanks to the support of the Edna McConnell Clark Foundation (USA), the World Health Organization's Programme for the Prevention of Blindness has prepared a set of documents, addressing the different aspects of trachoma control activities.

Blindness↗
PubMed1993

Childhood blindness: a new form for recording causes of visual loss in children.

The new standardized form for recording the causes of visual loss in children is accompanied by coding instructions and by a database for statistical analysis. The aim is to record the causes of childhood visual loss, with an emphasis on preventable and treatable causes, so that appropriate control measures can be planned. With this standardized methodology, it will be possible to monitor the changing patterns of childhood blindness over a period of time in response to changes in health care services, specific interventions, and socioeconomic development.

Abstracting and Indexing↗
PubMed1992

Epidemiologic aspects of global blindness prevention.

The number of blind persons in the world is not accurately known. However, taking into account previous estimates by the World Health Organization and adjusting to the world population of 1990, it is likely that there are at least 35 million blind people if we apply the internationally accepted definition of blindness as vision less than 3/60 ( less than 20/400 or 0.05) in the better eye. If the threshold of vision less than 6/60 ( less than 20/200 or 0.1) is applied, the above figure can be increased by roughly 50%, ie, going well beyond 50 million blind people. To this somber picture should be added the effects of aging on populations in both developed and developing countries. Longer life expectancy is going to dramatically increase the need for eye care to prevent visual loss from such conditions as cataract, glaucoma, diabetic retinopathy, and macular degenerations. Corneal blindness, resulting mainly from trachoma and other infections, is apparently showing a downward trend, but there are still foci of severe disease. Thus the need for trichiasis surgery remains, and some recently evaluated techniques offer particularly good results. On the other hand, xerophthalmia due to vitamin A deficiency is still a major public health problem, causing both visual loss and increased mortality. It should be possible, by targeting ivermectin distribution programs to high-risk populations, to gradually eliminate onchocerciasis as a cause of blindness; however, the long-term sight-saving effect of ivermectin in cases of established ocular lesions needs to be confirmed.

Africa↗
PubMed1992

[Epidemiological surveillance of trachoma: evaluation and perspective].

World Health Organization (W.H.O.) carried out a survey recently. This survey consisted in a questionnaire to some of its Member States to try to define the importance and world distribution of trachoma. The answers which have been sent by ocular health advisers and/or persons in charge of national ophthalmological institutes showed a systemic lack of significant data to be used for planning or for epidemiological surveillance. Nevertheless, the analysis of this survey seems to lead to the conclusion that trachoma is not still the main cause of blindness in some countries who used to be famous because of an important endemicity. However, trachoma is still a real ocular health and public health problem in numerous other countries, mainly in rural areas and- or areas which are away from socio-sanitary development areas. To have a better quality concerning epidemiological data and to obtain an easier regularity in their collecting, W.H.O. Program for the Blindness Prevention proposed a simplified coding system of trachoma and its complications (S.S.C.T.C.). If this system was accepted by numerous countries it would allow: the use of a simple, reliable and cheap tool to collect epidemiological informations which would constitute an help to take decisions to be able to, give a second start to epidemiological surveillance of trachoma, to have a better idea of the localization of endemic centres of the disease and of this impact on population, to define the needs concerning collective and individual medical and surgical treatments.

Blindness↗
PubMed1992

[Operational applications of the simplified coding system for trachoma and its complications].

In 1987, World Health Organization (W.H.O.) program for the Blindness Prevention proposed a simple system for coding and recording the various stages of Trachoma and its complications. Since this time, this system revealed to be a convenient and useful tool and was used in each epidemiological survey carried out together with Member States, either for blindness prevalence and causes studies as in Benin, Congo, Togo and Turkey, or for specific studies on Trachoma as in Vietnam, Morocco, Mali and in Kiribati. After a short presentation of the most significative results of these studies, the authors discuss on: 1--Details of practical use for this system in the field conditions, underlining particularly: training for future users; setting up of a study concerning reliability: this study has to be both easy an serious to allow an acceptable similarity between the observations of several examiners; some important points to calculate the size of the sample which has to be studied. 2--Main parameters and epidemiological signs which can be took on and invigilated thanks to this system.

Humans↗
PubMed1992

[Trachoma in the province of Ouarzazate, Morocco].

A survey on the prevalence and severity of trachoma was carried out in the province of Ouarzazate, Morocco. In conformity with the guidelines proposed by the WHO Programme for the Prevention of Blindness, a random sample of 30 clusters was extracted from the general population of the province, according to probability proportional to size. Thus, the sample comprised 1200 individuals, of whom 1185 were examined. Participation in the survey was 98.8% and, overall, the sample is considered representative of the province. The simplified grading system proposed by WHO was used to register the data on trachoma and its complications. The global prevalence of trachoma was estimated at 40.8% (95% confidence interval (95% CI) = 30.2-51.4%) and that of active trachoma (follicular (TF), intense (TI), and mixed (TF + TI)) at 18% (95% CI = 12.8-23.2%). The trachomatous intensity indicator (presence of TI) for children under 10 years of age was 12.8% (95% CI = 6.8-18.8%). The severity of the infection is confirmed by prevalences of trichiasis-entropion of 2.2% (95% CI = 1.4-3.0%) and central corneal opacity of 3.3%. Corneal blindness is estimated at 1.6%. The epidemiological pattern of trachoma merits particular attention in the field of public health, particularly in the valley of Oued Drâa, where all the indicators are consistently higher than those elsewhere in the province.

Adolescent↗
PubMed1990

[Prevalence and causes of blindness in the Congo].

A population-based survey on the prevalence of blindness and eye disease has been conducted throughout the Congo. This was the first time such a survey had been carried out in a central African country with an equatorial climate. In comparison with data available from other African countries, the two rather unexpected characteristics resulting from the survey were lower blindness prevalence rates and the extremely rare cases of bilateral corneal scarring. In accordance with sampling procedures recommended by the WHO Programme for the Prevention of Blindness, 7041 people were selected and examined. The prevalence of blindness (visual acuity less than 3/60 in the better eye) was 0.3% (5700 people). The prevalence of low vision (visual acuity between 6/24 and 3/60 in the better eye) was 2.1% (40,000 people). The major causes of blindness and low vision were cataract (81% and 80%, respectively) and glaucoma (9% and 3.4%, respectively). A total of 22,000 people in the Congo require cataract surgery. Almost four-fifths of the current burden of blindness in this country is potentially curable through the provision of cataract surgery and aphakic glasses.

Aged↗
PubMed1989

Water, trachoma and conjunctivitis.

The incidence of eye infections in a community is generally accepted as an indicator of the adequacy of water supply for their needs. However, discrepancies in the published results from various studies seem to challenge this view. We have reanalysed the published data on trachoma in relation to the most relevant indicators of water accessibility, using prevalence ratios as the single parameter for risk assessment. A definite trend emerges from this review: the incidence of infectious conjunctivitis is not sensitive to differences in water accessibility; on the other hand, a reduction in the risk of trachoma is consistently associated with better access to water. This conclusion may support the efforts of WHO and other multilateral and bilateral agencies to sustain the commitment towards the water supply sector beyond the International Drinking Water Supply and Sanitation Decade.

Climate↗