If a person can read letters at 20 feet that are readable at that distance to all people with normal vision, that person's visual acuity, or "eyesight", is said to be 20/20. If, on the other hand, a person is barely able to read letters at 20 feet that are readable at 40 feet to all people with normal vision.
Astigmatism
Astigmatism is a condition characterized by "blemishid vision"; that is, instead of light rays striking the retina in sharp focus, they spread out over a more or less diffuse area. Astigmatism is caused by the unequal curvature of either the cornea or the lens, sometimes both. Because the cornea and lens, are never optically perfect, most of us experience some degree of astigmatism. To correct astigmatism, the ophthalmologist prescribes glasses that compensate for the faulty curvatures of the refracting surfabes
HealthyCase - Giving Informations About Health
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By UrDocter
14 Jul 2010
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Visual Acuity and Optical Defects |
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By UrDocter
28 Oct 2010
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The Placenta and Placental HormonesThe placenta makes intrauterine life feasible. This structure is essentially a mass of blood sinuses formed by the placental septa. Into the sinuses extend chorionic projections from the fetal portion of the placenta, each covered with an enormous number of microscopic villi containing blood capillaries. Maternal blood flows into and out of these sinuses by means of a well-channeled system of vessels derived from the uterine wall. Fetal blood is led into the villi through the two umbilical arteries and then led back through the umbilical vein. As the blood moves through the villi, nutrients are absorbed and waste products are removed. |
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By UrDocter
18 Jan 2011
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Genital Herpes Cause Skin ProblemsTwo types of herpes simplex virus (HSV) cause skin problems. The common cold sore is usually caused by type 1, and type 2 usually infects the genital area. Occasionally type 1 herpes simplex virus can be found in the genital area. Genital infections- genital herpes-usually begin 3 to 7 days after exposure. The person may note an area of burning, tingling, or pain on the genitalia: then small, grouped blisters, which ulcerate, appear. Associated with these lesions may be severe pain, swollen lymph nodes, and constitutional symptoms such as fever. When the lesions appear on the cervix or vaginal wall, there are freruently no symptoms. |
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By HC Team
31 Jan 2011
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The Common Symptoms of Stress and AnxietyStress Symptoms appear differently for each person and they are affected by both external and internal factors. The external factors include the physical environment like jobs, relationships with other people, home, and more, whereas the internal factors define body’s ability to respond to as well as deal with everything happen every day. |
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By HC Team
02 Feb 2011
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Online Free Consultations and No Prescriptions DrugsWith a healthy body you don’t need to worry about everything. You can take your children to cinema in the weekend or you can finish the pending tasks at home. If it is an unfortunate situation that you are feeling unwell and going to doctor and get the prescriptions are not the choices you want to opt for at the moment, you can always go for internet for another solution. |
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| Visual Acuity and Optical Defects If a person can read letters at 20 feet that are readable at that distance to all people with normal vision, that person's visual acuity, or "eyesight", is said to be 20/20. If, on the other hand, a [ ... ] |
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