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.

Diseases and Disorders of the Nails

wound clean from pus

Blepharitis is an inflammation of the eyelids in which they become red, irritated and itchy and dandruff-like scales form on the eyelashes. It is a common eye disorder caused by either bacteria or a skin condition, such as dandruff of the scalp or acne rosacea. It affects people of all ages. Although uncomfortable, blepharitis is not contagious and generally does not cause any permanent damage to eyesight.

Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve.

The timing of the nausea or vomiting can indicate the cause. When appearing shortly after a meal, nausea or vomiting may be caused by food poisoning, gastritis (inflammation of the stomach lining), an ulcer, or bulimia. Nausea or vomiting one to eight hours after a meal may also indicate food poisoning.

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.

Pericardiocentesis is the aspiration of fluid from the pericardial space that surrounds the heart. This procedure can be life saving in patients with cardiac tamponade, even when it complicates acute type A aortic dissection and when cardiothoracic surgery is not available. [1] Cardiac tamponade is a time sensitive, life-threatening condition that requires prompt diagnosis and management. Historically, the diagnosis of cardiac tamponade has been based on clinical findings. Claude Beck, a cardiovascular surgeon, described 2 triads of clinical findings that he found associated with acute and chronic cardiac tamponade. The first of these triads consisted of hypotension, an increased venous pressure, and a quiet heart. It has come to be recognized as Beck's triad, a collection of findings most commonly produced by acute intrapericardial hemorrhage. Subsequent studies have shown that these classic findings are observed in only a minority of patients with cardiac tamponade. [2] The detection of pericardial fluid has been facilitated by the development and continued improvement of echocardiography. [3] Cardiac ultrasound is now accepted as the criterion standard imaging modality for the assessment of pericardial effusions and the dynamic findings consistent with cardiac tamponade. With echocardiography, the location of the effusion can be identified, the size can be estimated (small, medium, or large), and the hemodynamic effects can be examined by assessing for abnormal septal motion, right atrial or right ventricular inversion, and decreased respiratory variation of the diameter of the inferior vena cava.

1500 mg of sodium amounts to 0.75 teaspoons or 3.75 grams of salt per day, while 2300 mg amounts to one teaspoon or 6 grams of salt per day. Most people today are eating much more than that. The average intake of sodium is about 3400 mg, most of it coming from processed foods.

Early Signs that Cancer is Growing in Your Body

A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.

The syndrome of inappropriate antidiuretic hormone (ADH) secretion (SIADH) is defined by the hyponatremia and hypo-osmolality resulting from inappropriate, continued secretion or action of the hormone despite normal or increased plasma volume, which results in impaired water excretion.

A glucagonoma is a rare tumor of the alpha cells of the pancreas that results in the overproduction of the hormone glucagon. Alpha cell tumors are commonly associated with glucagonoma syndrome, though similar symptoms are present in cases of pseudoglucagonoma syndrome in the absence of a glucagon-secreting tumor.

Possible complications include: Cardiovascular disease. ... Nerve damage (neuropathy). ... Kidney damage (nephropathy). ... Eye damage (retinopathy). ... Foot damage. ... Skin conditions. ... Hearing impairment. ... Alzheimer's disease.

Narcolepsy is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep. People with narcolepsy often find it difficult to stay awake for long periods of time, regardless of the circumstances. Narcolepsy can cause serious disruptions in your daily routine. Sometimes, narcolepsy can be accompanied by a sudden loss of muscle tone (cataplexy) that leads to weakness and loss of muscle control. Cataplexy is often triggered by a strong emotion, most commonly laughter. Narcolepsy is a chronic condition for which there's no cure. However, medications and lifestyle changes can help you manage the symptoms. Support from others — family, friends, employer, teachers — can help you cope with narcolepsy.

CD4 T-cells (a type of white blood cell) are important to your body's defence against infections. This animation describes how your immune system is weakened by the HIV virus, which targets CD4 T-cells and leads to their gradual decline in number. Low to very low levels of CD4 cells put you at risk for 'opportunistic infections' that take advantage of the body's weakened immune system.

Vegetarian or Vegan? Can I recover?

The maneuver is commonly used during some activities: Straining to have a bowel movement Blowing a stuffy nose Certain medical tests or exams As a pressure equalization technique by scuba divers, sky divers and airplane passengers The effect of the Valsalva Maneuver is a drastic increase in the pressure within the thoracic cavity.

fingerprints and sweat glands