Flipping a Light Switch in the Cell: Quantum Dots Used for Targeted Neural Activation

New technique holds promise for better understanding of brain disorders

IMAGE: Optically excited quantum dots in close proximity to a cell control the opening of ion channels. Continue reading

New Imaging Technique Evaluates Nerve Damage

A new imaging technique could help doctors and researchers more accurately assess the extent of nerve damage and healing in a live patient. Researchers at Laval University in Québec and Harvard Medical School in Boston aimed lasers at rats’ damaged sciatic nerves to create images of the individual neurons’ insulating sheath called myelin. Physical trauma, repetitive stress, bacterial infections, genetic mutations, and neurodegenerative disorders such as multiple sclerosis can all cause neurons to lose myelin. The loss slows or halts the nerve’s transmission of electrical impulses and can result in symptoms such as numbness, pain, or poor muscle control.

Using their images of neurons, the researchers measured the thickness of the myelin at different locations Continue reading

VISION DISORDERS

Human vision is dependent on the successful interaction of optical structures in the eye. When these structures malfunction, vision disorders occur. The key to treatment and resolution of these disorders is early detection through regular eye exams and prompt consultation with an ophthalmologist when problems occur.

The best way to describe how vision works is to use the analogy of a camera. The pupil manages the incoming light rays, opening and closing—like a camera shutter—according to the amount of light available. These light rays are progressively refracted and focused by three structures: the cornea, a transparent, convex cover over the iris and pupil in front of the eye; the lens, a spherical body behind the cornea, and the vitreous humor, a gelatinous substance that fills the back of the eyeball. It is important that the rays be in sharp focus when they reach the retina, a sensory membrane that lines the back of the eye and acts like film in a camera. The retina converts the light rays into electrical signals that are sent to the brain by way of the optic nerve. The brain then translates these electrical signals into what we know as sight.

Refractive Errors. The most common vision disorders are refractive errors—specifically nearsightedness, farsightedness, and astigmatism. In each case, the eye does not refract the incoming light properly, so the image is blurred. While they are not diseases, refractive errors affect every age range and comprise the largest treatment effort of ophthalmologists. Refractive errors can be successfully corrected with eyeglasses, contact lenses, and laser refractive surgery.

Cataract. A cataract results when the normally transparent lens of the eye clouds, blurring vision. Most cataracts are age-related, advancing slowly and progressively until functional blindness occurs. Cataract cannot be prevented or cured with medication or optical devices, but it can be successfully treated through a surgical procedure that removes the damaged, natural eye lens and replaces it with a permanent, intraocular lens implant. The procedure has over a 90 percent success rate. After refractive errors, cataract is the most common vision disorder.

Macular Degeneration. Located in the retina, the macula is responsible for central vision. When people have macular degeneration, they can no longer bring the center of the picture they see into focus. The most common type of the disease is age related, and there are two forms: “wet” and “dry.” Whereas the wet form comprises only about 10 percent of cases, it causes the greatest vision loss, striking quickly and without warning as a result of erupting blood vessels. The dry form is characterized by a slow, progressive loss of vision from the thinning and tearing of the macula. Although both forms are being extensively researched, definitive causes and treatments have not yet been identified. Age-related macular degeneration is the leading cause of blindness in most developed countries.

Glaucoma. Glaucoma is a disease of the optic nerve. If the aqueous humor (the clear fluid that fills the front of the eye) does not drain properly, intraocular pressure builds, damaging the optic nerve and causing blind spots to develop. When the entire nerve is destroyed, blindness results. If glaucoma is detected and treated in the early stages, loss of vision can be averted. However, the disease is chronic and cannot be cured or reversed. Unfortunately, the early stages are symptomless. Once symptoms occur, usually manifested by loss of peripheral or side vision, irreversible vision loss has already taken place. Treatment consists of medication and/or surgery, depending on the type of glaucoma, the patient’s medical history, and the stage of the disease. Glaucoma is the leading cause of blindness worldwide and the second-leading cause in developed countries.

Diabetic Retinopathy. Retinopathy is a side effect of diabetes and occurs as a result of fluctuations in the body’s blood sugar, a daily problem for diabetics. When blood sugar fluctuates over time, it affects the blood vessels in various parts of the body, including the retina of the eye, where the blood vessels can break and bleed, causing blurred vision. The longer a person has diabetes, the higher the risk of retinopathy; good diabetic control can forestall the disease, however. Signs of retinopathy often occur before symptoms appear. Treatment includes the use of laser photocoagulation to seal leaking blood vessels. Often undetected and untreated, diabetic retinopathy is the leading cause of visual disability among working-age people.

Retinal Degeneration. Retinal degeneration is an umbrella term for a number of hereditary and degenerative disorders that range from mild to profound vision loss and blindness. Retinitis pigmentosa is the most common type of retinal degeneration, affecting one in three thousand people. Its many forms have widely varied symptoms, and onset and progress of the disease can be slow or rapid. In general, symptoms occur in childhood or young adulthood. Patients complain of night blindness followed by loss of visual field. There is no treatment, though researchers are hopeful that genetic therapies may be possible in the future.

Strabismus. Unlike most other vision disorders, strabismus is a physical defect. One or both of the eyes are misaligned and point in different directions. One eye may look ahead while the other eye points up, down, in, or out. Strabismus is more common in children than in adults. In adults it can be a side effect of head trauma or brain disorder. Treatment may involve eyeglasses, an eye patch (in some cases), or surgery on the eye muscles.

Different Anxiety Disorders

Anxiety disorders are the most common psychiatric disorders in the world. We take a look at these disorders.

Everybody feels anxious at times. Anxiety gears you up to face a threatening situation and rouses you to action. In general, it helps you cope.

But if you have an anxiety disorder, this normally helpful emotion can do just the opposite – it can keep you from coping and disrupt your daily life. Anxiety disorders aren’t just a case of “nerves”. They are illnesses, often related to the biological makeup and life experiences of the individual and they frequently run in families.

There are several types of anxiety disorders, each with its own distinct features. Many people have a single anxiety disorder. But it isn’t unusual for an anxiety disorder to be accompanied by another illness, such as depression, an eating disorder, substance abuse or another anxiety disorder.

What are the different types of anxiety disorders?

Phobias are the most common form of anxiety. (See the Post “ Phobias – 540 Common Phobias” . They are characterized by an intense, irrational and almost paralyzing fear of a specific situation or object. Adults with phobias realize their fears are irrational, but often facing, or even thinking about facing, the feared object or situation brings on a panic attack or severe anxiety.

Generalized anxiety disorder (GAD). People with GAD usually expect the worse and worry excessively about everyday life circumstances (such as their health, job, raising of children or finances), or minor matters (such as household chores or renovations – even just getting through the day becomes problematic). The person’s worries are much more than normal day-to-day anxiety. They are excessive, unrealistic, chronic and relentless.

Panic disorder. Panic attacks are characterized by a sudden rush of fear, usually accompanied by a pounding heart, shortness of breath, a choking or suffocating sensation or other physical symptoms. They often occur in response to a stressful situation or during a period of chronic emotional stress. Attacks can occur in the most familiar and seemingly non-threatening settings, at the grocery store, in church or while driving along a familiar road. Sufferers often describe a feeling of unreality during the attack. Someone experiencing a panic attack may feel on the verge of losing control or even dying.

Obsessive-Compulsive disorder (OCD). OCD is characterized by obsessions and compulsions. Obsessions are persistent, intrusive and unwanted thoughts; compulsions are repetitive behaviors or mental acts, often linked to obsessions. The obsessions and compulsions are distressing and time-consuming and often lead to impairment in functioning.

Post Traumatic Stress Disorder (PTSD). As a result of exposure to traumatic events, many people display symptoms such as intrusive memories of the event, nightmares, avoiding reminders of the event, feeling anxious or down, detachment from others, and a restricted range of emotions. A diagnosis of PTSD is made if these symptoms are present for more than three months and interfere with functioning.

Social Anxiety Disorder (SAD), also called Social Phobia, is an intense, persistent fear of being humiliated or embarrassed in social situations. Sufferers tend to think other people are very competent in public and that they are not. Small mistakes make appear much more serious than they really are. Blushing may seem painfully embarrassing, and they feel as though all eyes are focused on them. Exposure to the feared social situation or anticipation of the situation can produce an intense and immediate anxiety reaction, including physiological symptoms such as sweating and blushing.