The retina is a light-sensitive membrane located at the back of the eye. When light passes through the eye, the lens focuses an image on the retina. The retina converts the image to signals that it sends to the brain via the optic nerve. The retina works with the cornea, lens, and other parts of the eye and the brain to produce normal vision.
Retinal detachment occurs when the retina separates from the back of the eye. This causes loss of vision that can be partial or total, depending on how much of the retina is detached. Retinal detachment is a medical emergency. When your retina becomes detached, its cells may be deprived of oxygen. See your doctor immediately if you suspect you have retinal detachment.
If left untreated or if treatment of retinal detachment is delayed, you risk permanent vision loss.
Part 2 of 7: Types and Causes
Types and Causes of Retinal Detachment
There are three types of retinal detachment:
If you have a rhegmatogenous retinal detachment, you have a tear or hole in your retina. This allows fluid from within the eye to slip through the opening and get behind the retina. The fluid separates the retina from the membrane that provides it with nourishment and oxygen. The pressure from the fluid can push the retina away from the retinal pigment epithelium (RPE), causing the retina to detach. This is the most common type of retinal detachment.
Tractional retinal detachment occurs when scar tissue on the retina’s surface contracts and causes the retina to pull away from the back of the eye. This is a less common type of detachment that typically affects people with diabetes. Diabetes can lead to issues with the retinal vascular system and cause scar tissue in the eye that could cause detachment.
In exudative detachment, there are no tears or breaks in the retina. This type of detachment is caused by retinal diseases such as inflammatory disorder or Coats disease, which causes abnormal development in the blood vessels behind the retina.
A new method for measuring and imaging how quickly blood flows in the brain could help doctors and researchers better understand how drug abuse affects the brain, which may aid in improving brain-cancer surgery and tissue engineering, and lead to better treatment options for recovering drug addicts. The new method, developed by a team of researchers from Stony Brook University in New York, USA and the U.S. National Institutes of Health, was published today in The Optical Society’s (OSA) open-access journal Biomedical Optics Express.
The researchers demonstrated their technique by using a laser-based method of measuring how cocaine disrupts blood flow in the brains of mice. The resulting images are the first of their kind that directly and clearly document such effects, according to co-author Yingtian Pan, associate professor in the Department of Biomedical Engineering at Stony Brook University. “We show that quantitative flow imaging can provide a lot of useful physiological and functional information that we haven’t had access to before,” he says.
Drugs such as cocaine can cause aneurysm-like bleeding and strokes, but the exact details of what happens to the brain’s blood vessels have remained elusive—partly because current imaging tools are limited in what they can see, Pan says. But using their new and improved methods, the team was able to observe exactly how cocaine affects the tiny blood vessels in a mouse’s brain. The images reveal that after 30 days of chronic cocaine injection or even after just repeated acute injection of cocaine, there’s a dramatic drop in blood flow speed. The researchers were, for the first time, able to identify cocaine-induced microischemia, when blood flow is shut down—a precursor to a stroke.
Measuring blood flow is crucial for understanding how the brain is working, whether you’re a brain surgeon or a neuroscientist studying how drugs or disease influence brain physiology, metabolism and function, Pan said. Techniques like functional magnetic resonance imaging (fMRI) provide a good overall map of the flow of deoxygenated blood, but they don’t have a high enough resolution to study what happens inside tiny blood vessels called capillaries. Meanwhile, other methods like two-photon microscopy, which tracks the movement of red blood cells labeled with fluorescent dyes, have a small field of view that only measures few vessels at a time rather than blood flow in the cerebrovascular networks.
In the last few years, researchers including Pan and his colleagues have developed another method called optical coherence Doppler tomography (ODT). In this technique, laser light hits the moving blood cells and bounces back. By measuring the shift in the reflected light’s frequency—the same Doppler effect that causes the rise or fall of a siren’s pitch as it moves toward or away from you—researchers can determine how fast the blood is flowing.
It turns out that ODT offers a wide field of view at high resolution. “To my knowledge, this is a unique technology that can do both,” Pan said. And, it doesn’t require fluorescent dyes, which can trigger harmful side effects in human patients or leave unwanted artifacts—from interactions with a drug being tested, for example—when used for imaging animal brains.
Two problems with conventional ODT right now, however, are that it’s only sensitive to a limited range in blood-flow speeds and not sensitive enough to detect slow capillary flows, Pan explained. The researchers’ new method described in today’s Biomedical Optics Express paper incorporates a new processing method called phase summation that extends the range and allows for imaging capillary flows.
Another limitation of conventional ODT is that it doesn’t work when the blood vessel is perpendicular to the incoming laser beam. In an image, the part of the vessel that’s perpendicular to the line of sight wouldn’t be visible, instead appearing dark. But by tracking the blood vessel as it slopes up or down near this dark spot, the researchers developed a way to use that information to interpolate the missing data more accurately.
ODT can only see down to 1-1.5 millimeters below the surface, so the method is limited to smaller animals if researchers want to probe into deeper parts of the brain. But, Pan says, it would still be useful when the brain’s exposed in the operating room, to help surgeons operate on tumors, for example.
The new method is best suited to look at small blood vessels and networks, so it can be used to image the capillaries in the eye as well. Bioengineers can also use it to monitor the growth of new blood vessels when engineering tissue, Pan said. Additionally, information about blood flow in the brain could also be applied to developing new treatment options for recovering drug addicts.
Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and extremities. Syringomyelia may also cause a loss of the ability to feel extremes of hot or cold, especially in the hands. The disorder generally leads to a cape-like loss of pain and temperature sensation along the back and arms. Each patient experiences a different combination of symptoms. These symptoms typically vary depending on the extent and, often more critically, to the location of the syrinx within the spinal cord.
Image: An idiopathic syrinx. See the thin light grey shape inside the spinal cord, placed at centre in the bottom half of the above image.
The above EKG shows an example of complete heart block. This rhythm is an idioventricular rhythm. The distinguishing characteristic is that no P waves from the atria are conducted to the ventricles. A careful examination will show that the PR interval is random as a result of there being no relationship between the P wave and the QRS complex. This is also referred to as AV dissociation. The QRS complex in this rhythm actually originates in the ventricles (we know this because there is no relationship between the P wave and the QRS and because the QRS complex is wide, nearly .36 seconds) and the effective heart rate is 33 beats per minute.
In patients with liver problems, one of the 1st places to monitor for jaundice is the SCLERA. By the time it reaches the skin, the patient will start itching A LOT! So, remember to maintain good skin care.