Extrusion of subducted crust explains the emplacement of far-travelled ophiolites.

Continental subduction below oceanic plates and associated emplacement of ophiolite sheets remain enigmatic chapters in global plate tectonics. Numerous ophiolite belts on Earth exhibit a far-travelled ophiolite sheet that is separated from its oceanic root by tectonic windows exposing continental crust, which experienced subduction-related high pressure-low temperature metamorphism during obduction. However, the link between continental subduction-exhumation dynamics and far-travelled ophiolite emplacement remains poorly understood.

Blindness and low vision in Cape Verde Islands: results of a national eye survey.

Aims: Prior to establishing a national prevention of blindness program a population based survey was conducted in Cape Verde Islands in1998. The objectives of the survey were to estimate the overall and age-specific prevalence of blindness and low vision, to identify the main disorders causing blindness and low vision, and to estimate the population need for basic eye care services.

Methods: A two-level cluster random sampling procedure was used, selecting 30 clusters from the nine inhabited islands and 3,803 persons of all ages were included in the sample.

[Strategies to control cataracts].

Cataracts, often associated with aging (80%), are a major cause of blindness (more than 50% of cases of blindness in Africa), and for this reason, up to 80% of cases could be predicted or prevented. The socio-economic costs (care and loss of productivity) are increased by morbidity (blindness, impaired vision, congenital, complicated or infected cataracts). The biological determinants of cataracts account for the difficulties in developing and implementing effective preventive action.

[Synthesis of the blindness situation in the countries of the Organization for Cooperation and Coordination in the Control of Major Endemic Diseases].

The major causes of blindness in the OCCCMED states are cataracts, trachoma, glaucoma and oncocercosis. The prevalence of blindness is about 1.2% and there are about 880,000 blind individuals and 2,500,000 people with impaired vision.