In the emmetropic eye (with normal refraction), the incident light rays are focused by the cornea and the lens onto the retina, creating a sharp image that is transmitted to the brain. The lens is elastic in particular in younger people. During accommodation, the ciliary muscle adjusts the lens shape so that properly focused images. Refractive error inability of the eye to focus images sharply on the retina are. The result is blurred vision (refractive errors). Refraction (A) emmetropia, (B) myopia, (C) hyperopia, (D) astigmatism. In myopia (nearsightedness), the focus is in front of the retina because the cornea is too curved, the eye axis is too long or both. Objects in the distance are blurred, while objects are clearly visible in the vicinity. For correction of myopia concave (minus) used glasses. Myopic refractive errors take in children frequently until the completion of the size growth. In hyperopia (farsightedness), the focus behind the retina is because the cornea is too flat, the axial length is too short, or both. both near and far objects are blurred in adults. Children and young adults with mild farsightedness have to accommodate because of their ability may be able to achieve a good visual performance. For the correction of hyperopia convex (positive) can be used glasses. In astigmatism, causes a non-spherical (variable) of curvature of the cornea or the lens, that light beams of different orientations (eg. B. vertical, slanted, horizontal) are focused at different points. Astigmatism is corrected by the cylindrical lenses (cylindrical segments). Cylinder glasses do not refract light in one axis and are concave or convex in the other axis. In presbyopia (presbyopia), the lens loses with age the ability to change shape to focus on objects nearby. Typically, a presbyopia makes from early / mid-forties noticeable. A convex lens (positive lens) is used for correction when objects are viewed in the vicinity. This correction glasses can be used as separate glasses or bifocals or progressive lenses incorporated into. Anisometropia is a significant Refraktionsunterschied between both eyes (usually> 3 diopters). The correction lenses leads to a difference in size of the retinal images (aniseikonia). This can lead to difficulties merger of the two different sized images and even to suppress an image. Symptoms and complaints The primary symptom of refractive errors is blurred vision of distant objects nearby objects, or both. Sometimes the excessively strong Ziliarmuskeltonus can cause headaches. Longer squint and frown when using the eye can also cause headaches. Occasionally, excessive staring can lead to drying of the eye surface with irritated, itchy, tired eyes, foreign body sensation and redness. Frown when reading and massive blinking or eye rubbing are symptoms of refractive errors in children. Diagnostic testing visual acuity Refraction Comprehensive eye exam visual acuity test and refraction (determination of refractive error) should be performed as needed every 1 or 2 years. The screening of visual acuity of children helps to uncover refractive error in time, before they lead to learning difficulties. A comprehensive eye examination (examination in eye diseases), which should be done by an ophthalmologist or optometrist should accompany the refraction. Therapy eyewear lenses Refractive Surgery treatment of refractive errors include corrective lenses, contact lenses (contact lenses) and refractive surgery (photorefractive keratectomy). Myopia and hyperopia be corrected with spherical lenses. Concave lenses are used to treat myopia. They are minus or divergent lenses. Convex lenses are used to treat hyperopia. They are plus or convergent lenses. Astigmatism is treated with cylindrical lenses. A recipe for corrective lenses include 3 numbers. The first number represents the thickness (height) of the required spherical correction (minus for myopia; Plus at hyperopia). The second number stands for the thickness of the necessary cylindrical correction (plus or minus). The third number describes the axis of the cylinder. For example, a prescription for a person with myopic astigmatism -4.50 + 2.50 × 90 would read, and a recipe for a person with hyperopic astigmatism would read +3.00 + 1.50 × 180th

Health Life Media Team

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