The eyes A close up of a young person's eyes. The eyes are responsible for four-fifths of all the information our brain receives. Here you can find out a bit more about how they work, common problems that affect vision and the work Sightsavers does to treat and prevent avoidable blindness. You can also find out more about the people whose lives have been changed thanks to donations from people like you. How do eyes work? (click image to see enlarged version or click here for text alternative) Graphic of an eye with information about its different parts The images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea. Because this part of the eye is curved, it bends the light, creating an upside down image on the retina (this is eventually put the right way up by the brain). The retina is a complex part of the eye, but only the very back of it is light sensitive. This part of the retina has roughly the area of a 10p coin, and is packed with photosensitive cells called rods and cones. Cones are the cells responsible for daylight vision. There are three kinds – each responding to a different wavelength of light: red, green and blue. The cones allow us to see images in colour and detail. Rods are responsible for night vision. They are sensitive to light but not to colour. In darkness, the cones do not function at all. How do we see an image? The lens focuses the image. It can do this because it is adjustable – using muscles to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain. Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.

Magnetic resonance imaging (MRI) can be an important tool in the diagnosis of multiple sclerosis (MS). MRI can also be used to monitor the progression of the disease in people living with MS. How does it work? MRI uses very strong magnets, radio signals, and computer software to take 3-dimensional pictures of the inside of the body. Will I need contrast material? Maybe. Contrast material is a substance that temporarily changes the way imaging tools interact with the body. They are often used to visualize certain types of MS disease activity on the MRI. If your doctor thinks your scan requires this contrast material, you may get an injection before you get in the MRI machine. How long will it take? The time may vary based on the type of MRI. Be sure to discuss with your doctor in advance so he or she can provide you with exact timing. But don’t worry, you won’t have to stay still the whole time. The technician will let you know when they’re starting a new image.

Technically, there's no formal definition for a "Code", but doctors often use the term as slang for a cardiopulmonary arrest happening to a patient in a hospital or clinic, requiring a team of providers (sometimes called a "code team") to rush to the specific location and begin immediate resuscitative efforts.

A heart attack is a medical emergency. A heart attack usually occurs when a blood clot blocks blood flow to the heart. Without blood, tissue loses oxygen and dies. Symptoms include tightness or pain in the chest, neck, back, or arms, as well as fatigue, lightheadedness, abnormal heartbeat, and anxiety. Women are more likely to have atypical symptoms than men. Treatment ranges from lifestyle changes and cardiac rehabilitation to medications, stents, and bypass surgery.

Keratoplasty is the procedure whereby abnormal corneal tissue is replaced by a healthy donor cornea.

Ankle fusion (arthrodesis) This is a surgical procedure which joins together the main bones of the ankle joint (the tibia and the talus). However, depending on the technique your surgeon will use, occasionally the fibula will be included in this procedure. The two joint surfaces which generate the pain are removed.

If it gets more severe and causes symptoms, your low hemoglobin count may indicate you have anemia. A low hemoglobin count is generally defined as less than 13.5 grams of hemoglobin per deciliter (135 grams per liter) of blood for men and less than 12 grams per deciliter (120 grams per liter) for women.

An intelligence quotient (IQ) is a total score derived from one of several standardized tests designed to assess human intelligence. IQ is a number meant to measure people cognitive abilities (intelligence) in relation to their age group. An I.Q between 90 and 110 is considered average; over 120, superior. Roughly 68% of the population has an IQ between 85 and 115. The average range between 70 and 130, and represents about 95% of the population.

The rotator cuff is a group of muscles and tendons that surround the shoulder joint, keeping the head of your upper arm bone firmly within the shallow socket of the shoulder. A rotator cuff injury can cause a dull ache in the shoulder, which often worsens when you try to sleep on the involved side. Rotator cuff injuries occur most often in people who repeatedly perform overhead motions in their jobs or sports. Examples include painters, carpenters, and people who play baseball or tennis. The risk of rotator cuff injury also increases with age. Many people recover from rotator cuff disease with physical therapy exercises that improve flexibility and strength of the muscles surrounding the shoulder joint. Sometimes, rotator cuff tears may occur as a result of a single injury. In those circumstances, medical care should be provided as soon as possible. Extensive rotator cuff tears may require surgical repair, transfer of alternative tendons or joint replacement.

Mitral valve repair of anterior leaflet perforation and ruptured chordae

Cancer starts when cells in a part of the body begins to grow out of control and can spread to other areas of the body. There are many kinds of cancer. Cells in nearly any part of the body can become cancer. To learn more about how cancers start and spread, see What Is Cancer? Leukemias are cancers that start in cells that would normally develop into different types of blood cells. Here we will talk about acute myeloid leukemia (AML). Acute myeloid leukemia (AML) has many other names, including acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia, and acute non-lymphocytic leukemia. “Acute” means that this leukemia can progress quickly if not treated, and would probably be fatal in a few months. “Myeloid” refers to the type of cell this leukemia starts from. Most cases of AML develop from cells that would turn into white blood cells (other than lymphocytes), but some cases of AML develop in other types of blood-forming cells. The different types of AML are listed in “ How is acute myeloid leukemia classified?” AML starts in the bone marrow (the soft inner part of certain bones, where new blood cells are made), but in most cases it quickly moves into the blood. It can sometimes spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles. Other types of cancer can start in these organs and then spread to the bone marrow. But these cancers that start elsewhere and then spread to the bone marrow are not leukemias. Normal bone marrow, blood, and lymphoid tissue To understand the different types of leukemia, it helps to know about the blood and lymph systems.

Multiple endocrine neoplasia type 2 (MEN2) is a hereditary condition associated with three primary types of tumors: medullary thyroid cancer, parathyroid tumors, and pheochromocytoma. MEN2 is classified into three subtypes based on clinical features. MEN2A, which affects 60% to 90% of MEN2 families Medullary thyroid cancer: 98% to 100% with MEN2A are affected Pheochromocytoma, a typically benign (noncancerous) tumor of the adrenal glands: 50% with MEN2A affected Parathyroid adenoma (benign tumor) or hyperplasia, meaning increased size, of the parathyroid gland: 5% to 10% with MEN2A affected MEN2B, which affects 5% of MEN2 families Medullary thyroid cancer: 98% to 100% with MEN2B affected Pheochromocytoma: 50% with MEN2B affected Mucosal neuromas, which is a benign tumor of nerve tissue on the tongue, lips and throughout the gastrointestinal tract: 95% to 98% affected Digestive problems caused by disordered nerves in the gastrointestinal tract: 75% to 90% affected Muscle, joint, and spinal problems: 95% affected Typical facial features, including swollen lips and thick eyelids: 75% to 90% affected Familial medullary thyroid cancer (FMTC), which affects 5% to 35% of MEN2 families Medullary thyroid carcinoma only Sources: Gagel RF, Marx SJ. “Multiple endocrine neoplasia.” Williams Textbook of Endocrinology, Chapter 40, 11th ed., Philadelphia, 2008, and Eng C, Clayton D, et al. Grubbs EG, Gagel RF. My, How Things Have Changed in Multiple Endocrine Neoplasia Type 2A! J Clin Endocrinol Metab 100(7):2532-5, 7/2015. PMID: 26151398. What causes MEN2? MEN2 is a genetic condition. This means that the cancer risk and other features of MEN2 can be passed from generation to generation in a family. The gene associated with MEN2 is called RET. A mutation (alteration) in the RET gene gives a person an increased risk of developing medullary thyroid cancer and other tumors associated with MEN2.

Vediographic-Electric Beat-Pacemakers and the human heart

new Anti-Choking Device.

Endotracheal intubation is a medical procedure in which a tube is placed into the windpipe (trachea) through the mouth or nose. In most emergency situations it is placed through the mouth. Whether you are awake (conscious) or not awake (unconscious), you will be given medicine to make it easier to insert the tube. After endotracheal intubation, you will likely be placed on a breathing machine. If you are awake after the procedure, your health care provider may give you medicine to reduce your anxiety or discomfort.

Retro-sigmoid craniotomy (often called "keyhole" craniotomy) is a minimally-invasive surgical procedure performed to remove brain tumors. This procedure allows for the removal of skull base tumors through a small incision behind the ear, providing access to the cerebellum and brainstem. Neurosurgeons may use this approach to reach certain tumors, such as meningiomas and acoustic neuromas (vestibular schwannomas).

Immunotherapy cancer trial cures 90% of participants.

Surgical Skin Closure Procedures

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