The iris is the colored muscle, called the sphincter muscle, of the eye that expands and contracts the pupil to control the amount of light entering the eye. In an eye that functions properly, the pupil will appear larger in low light and look...
Contrast sensitivity is a measurement of your eyes' ability to distinguish between different objects in a scene, typically ones that are overlapping, poorly outlined and similarly colored. While someone with high contrast sensitivity may be able...
The eye pupil is the hole in the middle of the iris, the colored part of the eye. Pupils dilate and shrink in response to light; two muscles control pupil size, according to "Fundamentals for Ophthalmic Personnel." Pupillary reactions are...
Head injuries include trauma to the scalp, skull and brain. According to the U.S. Centers for Disease Control and Prevention (CDC), 1.7 million traumatic brain injuries (TBIs) occur annually in the United States, causing 52,000 deaths. Of greatest...
Cocaine is a highly addictive drug that is illegal in the United States. According to Drugs.com, the powder form of cocaine can be snorted up the nose or rubbed on areas of the skin like the gums or genitals. The powder can also be mixed with...
Drug use, whether prescription, over-the-counter or illegal drugs, causes side effects in many people. If a person has known sensitivities to drugs or other substances, he should take time to consider the possible complications. A number of these...
The National Survey on Drug Use and Health, published by the U.S. Department of Health and Human Services, reports data on alcohol and illicit drug use. The most recent survey, published in 2008, states that approximately 22.2 million people in...
Running helps to improve your overall health and may also enhance your eyesight. By triggering a stress response in your body and increasing blood flow to your eyes, running can provide a temporary boost to your ability to distinguish between...
Your eye doctor will measure your pupil size in millimeters in both light and dark conditions. He will try to assess whether or not the pupils are significantly different in dilation from one another, a key indicator of anisocoria. Doctors may...
Miotics are a group of drugs that are used in the treatment of glaucoma. Glaucoma is a disease of the eyes that eventually causes damage to the optic nerve and leads to blindness. According to the Glaucoma Learning Center, miotics are effective...
During an eye examination, the doctor looks through the pupils to physically inspect the anterior chamber of the eyes. By use of dilating drops, he can temporarily paralyze the muscles that control the iris, roughly doubling the size of the...
The benefits of physical activity are varied, with exercise enthusiasts and researchers alike extolling its virtues for a number of indices of physical and mental well-being. As your eyes and brain both play a role in determining how well you see,...
A cluster headache is a type of head pain that occurs multiple times in a short period. After a respite of weeks to months another cluster of painful attacks can occur. Although the length and timing of cluster headaches vary among individuals,...
According to the Mayo Clinic, neuroblastoma is a form of cancer that originates from nerve cells. Sometimes, this cancer can form in your adrenal gland (located above your kidneys), stomach, chest and pelvis. Typically, neuroblastoma affects...
Brain hemorrhage is a serious brain condition where bleeding occurs from a ruptured blood vessel. If the brain hemorrhage is localized to one hemisphere of the brain, it is called a lobar intracerebral hemorrhage. However, a deep intracerebral...
A brain bleed is a medical emergency that occurs when you have head trauma or suffer a stroke. Brain bleeds can occur within your brain (intracranial hemorrhage) or on the outer portions of your brain (subarachnoid hemorrhage). Sometimes the blood...
The pupil is the tiny dark hole in the center of the iris that dilates or constricts in response to the amount of light available and emotional states such as fear. The iris’s two muscles control the pupil’s size. Disorders that...
Percocet is the combination of oxycodone and acetaminophen used to treat moderate to severe pain, according to the National Library of Medicine (NLM). RxList.com notes that Percocet works by affecting parts of your brain that interpret pain...
Anxiety is defined as the apprehensive feelings that result from a non-specific threat. An article in the April 2002 edition of "Outside Magazine" titled "At Home in the Discomfort Zone" provides a detailed distinction between fear and anxiety....
A concussion is considered to be a mild brain injury that results from a blow to the head, according to MayoClinic.com. The force of the injury causes bruising and swelling, which can lead to several symptoms. Immediate symptoms of a concussion...
Frontal lobe brain tumors can be cancerous or noncancerous. Both types of tumors can cause symptoms for a variety of reasons. Tumors can destroy brain cells, causing permanent brain damage and inflammation as well as placing pressure on tissues...
Iritis is an inflammation of the iris, the colored area of the eye. The iris constricts or dilates to control the size of the pupil, the black area at the center of eye. By controlling pupil size, the iris moderates the amount of light that enters...
Headaches are a common cause of disability in both men and women, according to the online medical library Merck Manuals. Though their effects can be debilitating, headaches are only very rarely due to a serious disorder. Headaches that are not...
A cerebrovascular incident, or stroke, is a compromise of the blood vessels to deliver blood to an area of the brain, potentially causing brain damage. It can either be an occlusion of the vessel lumen, known as ischemic stroke, or a rupture of...
Headaches can cause pain on several areas of the head. They rank among the most common pain problems and come in various forms. Depending on the type of headache and its cause, headaches can last for hours or persist for months. Daily headaches...
Peripheral neuropathy is damage to the nerves in the extremities such as the feet, legs, toes, fingers and hands. It comes from many different injuries or diseases. Some of them are AIDs, uremia, damage from nerve compression or entrapment,...
The human body is made up of several main systems, one of which is the muscular system. There are hundreds of muscles within the body, including more than 400 skeletal muscles alone. They are responsible for more than 40 percent of a person's...
A tumor that starts in the brain occurs in more than 35,000 people every year in America, notes the National Cancer Institute. Tumors in the brain are either benign (not cancer) or malignant (cancer). Tumors in the brain "directly destroy brain...
