Adaptability of cashpoints for the disabled

6.6 Glossary of sensory disability terminology (providedby ONCE)GLOSSARYVISUAL SHARPNESSThe measurement of visual sharpness forms the first part of ocular examination.Visual sharpness means the degree of aptitude the eye has to perceive spatialdetails, these being measured by the angle below which they are seen. Thesmaller this angle, the greater is the visual sharpness.To measure it, optotypes or panels of letters or symbols are generally used.These letters or symbols are arranged in lines, gradually reducing their sizeand their design is adjusted to norms of size, thickness and separationbetween them. Each line shows the distance at which the letters or thesymbols can be clearly identified by a person with “normal” vision.Visual sharpness is determined in each eye separately and with the bestcorrection with glasses or contact lenses that the person needs. To measureit the person sits facing the optotype at the distance for which it is prepared(usually 6 m). If they see all the figures, their visual sharpness will be theunit (1), which corresponds to normal vision. If they cannot see all the lines,then the smallest one that they can see is noted down.The notation of visual sharpness may be decimal (0.1- 0.2…) or in the formof a fraction (the numerator indicates the distance between the personevaluated and the optotype, and denominator the distance at which thenormal eye could identify the stimulus shown).Visual sharpness must be measured from both far away and close-up.VISUAL FIELDThe area of space that the eye sees is called the visual field. Visual fields areexamined in order to diagnose ophthalmologic pathologies, to study theirlocation within the visual system and control its evolution.Visual sensitivity is greater in the central part of the visual field, this pointcorresponding to the fovea and decreasing as it moves further away towardsthe more peripheral areas. Therefore the objects situated in the centre orclose to it are clearly seen whereas by going towards the periphery the sizeof the objects must be greater to be seen.72 ADAPTABILITY OF CASHPOINTS FOR THE DISABLED