Visual acuity is a function that expresses the visual discriminative capacity. As a central visual acuity, we understand competence recognition angle between two points in space. But there is a cognition as part of the process of measuring the vision, its understanding is common and well operated by ophthalmologists. Its measurement can be obtained through the relation between the least significant portion of an object (optotypes) and distance between observer and object. To this end, symbols in black on white background are used (for maximum contrast) and placed at a known distance (for instance twenty feet, or six meters) of examined. The misidentification of optotypes can be by a distance over the object to the observer (above the visual capacity of the eye normal human) limited by other reasons such as diffraction, the aberration and dispersion. These phenomena occur along with the optical blurring visual. In diffraction, there is a change in direction of light when the it encounters an obstacle. It can be seen in eyes with small pupils Optical aberration involves bending of light and only occurs where the refractive indices are different, and higher this difference, more the deviation of light rays .. The dispersion is important in situations as corneal edema and lens, when water infiltrated between the corneal lamellae represents a great increase in space to avoid interference optics. However, it will suffer only deviation is the distance between diopter with different refractive indices is higher than its wavelength (600 nanometers). A clear vision involves some blurring, however even in sub-optimal central nervous system can be activated in order to filter out the lack of clear limits, and result in a perceived scene as clear. also the lack of light can be compensated by the brain, which acts as an image intensifier. . The view underwater is affected by many factors, including the low light, especially at greater depths. Around 30 m deep, the light spectrum is limited and difficult to color discrimination. Professional divers are exposed to adverse underwater visibility. The search for objects at great depths assumes an important discriminatory ability. Divers Amateurs often do not understand details of the environment that surrounds them, either through lack of familiarity with the search or possibly by optical and other cognitive factors. The aim of this study is to assess visual acuity in professional divers and non-divers varying the brightness of the target (low contrast) and visual blurring. We intend to study the adaptive response of the central nervous system, eventually increase the sharpness of objects and the contrast by training, improving the visual acuity measured in this subgroup. We will test the view of divers and non divers volunteers with appropriate optical correction (glasses) is required (under vision 20/20), at low contrast and the best view under blurring and lens 1d (induced myopia). It will be measured in high-contrast vision through water blurred by comparing the two groups, and finally photographed the table visual acuity through turbid water, for comparison of optiotipos determination of directly observed and the photographs.
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