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Global Positioning System (GPS)

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Introduction GPS is incorporated in many of our daily objects and serve many purposes in our daily navigation. Drivers use GPS when navigating streets, pedestrians use GPS on mobile devices to navigate walking paths, and GPS devices are being used to monitor human and animal movement. In addition, many recreational uses, such as hiking, use GPS to track locations. GPS is defined as “A system of radio-emitting and -receiving satellites used for determining positions on the earth. The orbiting satellites transmit signals that allow a GPS receiver anywhere on earth to calculate its own location through trilateration. Developed and operated by the U.S. Department of Defense, the system is used in navigation, mapping, surveying, and other applications in which precise positioning is necessary.” (ESRI, GIS Dictionary, GPS) Background on GPS For GPS units to properly locate your position, this requires the three components: space segment, control section and user seg
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UV, Sunscreen, and SPF

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What is SPF Sunscreen? SPF, or  Sun Protection Factor ,is a measure of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn, damages skin, and can contribute to skin cancer. If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate that depends on skin type, intensity of sunlight and amount of sunscreen used. SPF is actually a measure of protection from amount of UVB exposure and it is not meant to help you determine duration of exposure. For best protection, experts recommend using a minimum SPF sunscreen of 15, applying the proper amount (2mg/cm 2  of skin, or about one ounce for full body coverage), and reapplying every 2 hours. Most people under-apply sunscreens, using ¼ to ½ the amount required. Using half the required amount of sunscreen only provides the squa
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Trichiasis

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Symptoms and Treatment Your eye may feel irritated by the sensation of having something in your eye. Other symptoms include: redness tearing , and sensitivity to bright light Eyelashes that rub against the cornea for a long time can cause a  corneal abrasion  or even a  corneal ulcer . How is trichiasis treated? Other surgical treatments include: Electrolysis . This process uses electricity to permanently remove hair. While effective, electrolysis is time-consuming and can be painful. Cryosurgery . This removes the lashes and follicles by freezing them. Cryosurgery is effective but has the potential for complications. Your ophthalmologist may recommend surgery to reposition the eyelashes. This can be the case if your trichiasis is due to epiblepharon.
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Stye

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A   stye , also known as a   hordeolum , is a bacterial infection of an   oil gland   in the   eyelid . The outside or the inside of the eyelid can be affected. Signs and symptoms Stye of the upper eyelid 8-year-old boy with an external hordeolum of lower lid The first sign of a stye is a small, yellowish spot at the center of the bump that develops as  pus  and expands in the area. [7] Other stye symptoms may include: A lump on the top or bottom  eyelid Localized swelling of the eyelid Localized  pain Redness Tenderness Crusting of the eyelid margins Burning in the eye Droopiness of the eyelid Scratchy sensation on the  eyeball  (itching) Blurred vision Mucous discharge in the eye Irritation of the eye [8] Light sensitivity Tearing Discomfort during blinking [9] Sensation of a foreign body in the eye Complications [ edit ] chalazion   lid deformity or lid  fistula . Large styes may interfere with one's vision. Eyelid  celluliti
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Retinoblastoma

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A rare form of eye cancer, retinoblastoma is the most common form of cancer affecting the eye in children. Retinoblastoma may occur in one or both eyes. Symptoms Eye swelling A white color in the center circle of the eye (pupil) when light is shone in the eye, such as when taking a flash photograph Eyes that appear to be looking in different directions Eye redness Causes Autosomal dominant inheritance pattern Open pop-up dialog box Retinoblastoma occurs when nerve cells in the retina develop genetic mutations. These mutations cause the cells to continue growing and multiplying when healthy cells would die. This accumulating mass of cells forms a tumor. Retinoblastoma cells can invade further into the eye and nearby structures. Retinoblastoma can also spread (metastasize) to other areas of the body, including the brain and spine. In the majority of cases, it's not clear what causes the genetic mutations that lead to retinoblastoma. However, it's possibl
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Orthokeratology

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Ortho-K And Corneal Refractive Therapy: Overnight Contacts To Correct Myopia Wouldn't it be great if you could correct your eyesight and reduce your dependence on  glasses  or  contact lenses  — without having to undergo eye surgery? It might sound far-fetched, but it's a reality for many people. It's called orthokeratology, or ortho-k. Here are the top 10 things you should know about orthokeratology: 1. What Is Ortho-K? Ortho-k lenses are prescribed for two purposes: To correct refractive errors (primarily  nearsightedness , but also  astigmatism  and  hyperopia ). In some cases, ortho-k also is used to correct  presbyopia . To slow the progression of childhood myopia. ( Read more about myopia control. ) Ortho-k lenses are also called "corneal reshaping contact lenses" or "overnight contact lenses to correct or control myopia." One specific brand of ortho-k lenses and fitting technique is Bausch + Lomb's Vision Shaping Treatment
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Diabetic retinopathy

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Diabetic retinopathy is a diabetes complication that affects eyes. It's caused by damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina). Symptoms You might not have symptoms in the early stages of diabetic retinopathy. As the condition progresses, diabetic retinopathy symptoms may include: Spots or dark strings floating in your vision (floaters) Blurred vision Fluctuating vision Impaired color vision Dark or empty areas in your vision Vision loss Causes Diabetic retinopathy Open pop-up dialog box Over time, too much sugar in your blood can lead to the blockage of the tiny blood vessels that nourish the retina, cutting off its blood supply. As a result, the eye attempts to grow new blood vessels. But these new blood vessels don't develop properly and can leak easily. There are two types of diabetic retinopathy: Early diabetic retinopathy. Advanced diabetic retinop
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