Sunday Mirror www.nationalmirroronline.net
Sunday, November 3, 2013
Know your organs
An eye is a round-shaped organ that works with the brain to provide us with vision. The eye is about 2.5 cm in length, weighs about seven grams and is shaped roughly like a ball. It sits in a special place in your skull called the eye socket. When you look in the mirror you can see several parts of your eye. The white part is called the sclera. The sclera is very tough and covers most of your eye. The first thing light touches when entering the eye is a thin veil of tears that coats the front of the eye. Behind this lubricating moisture is the front window of the eye, called the cornea. This clear covering helps to focus the light. On the other side of the cornea is more moisture. This clear, watery fluid is the aqueous humor. It circulates throughout the front part of the eye and keeps a constant pressure within the eye. After light passes through the aqueous humor, it passes through the pupil. This is the central circular opening in the colored part of the eye, also called the iris. Depending on how much light there is, the iris may contract or dilate, limiting or increasing the amount of light that gets deeper into the eye. This focused light now beams through the center of the eye. Again the light is bathed in moisture, this time in a clear jelly known as the vitreous. Surrounding the vitreous is the retina. The retina is the inner lining of the back of the eye. It’s like a movie screen or the film of a camera. The focused light is projected onto its flat, smooth
The Eye surface. The retina has many working parts such as the blood vessels which bring nutrients to the retina’s nerve cells. The macula is the bull’s-eye at the centre of the retina. The dead center of this bull’s eye is called the fovea. Because it’s at the focal point of the eye, it has more specialized, light sensitive nerve endings, called photoreceptors, than any other part of the retina. There are two kinds of photoreceptors: rods and cones. These specialized nerve endings convert the light into electrochemical signals. There are about 120 million rods and about 7 million cones in each eye! The rods and cones send all the information they gather through the optic nerve at the back of the eye. The brain then uses the nerve signals to put together a picture of the outside world. The place in the retina where the optic nerve exits is called the blind spot. This is because there are no rods or cones in this area, and if an image is projected onto this part of the retina, you cannot see it. The optic nerve sends the visual signals to the visual center in the back of the brain where the experience of vision occurs. Now light, reflected from an object, has entered the eye, been focused, converted into electro-chemical signals, delivered to the brain and interpreted or “seen” as an image. The eye also has a couple of ways to protect itself. The biggest protection for the eye is the eyelid. The eyelid helps to keep the eye clean and moist. Some common conditions that afflict the eye are Glaucoma; Farsightedness Nearsightedness; Pink Eye; Blindness; Astigmatism; Cataracts and Dry Eye Syndrome. Here are some warning signs of eye problems: Difficulty adjusting to darkness; Double vision; Red eyes; Crusty or swollen eyes; Recurring pain in or around the eyes; Excessive tearing or watering; Very dry, itchy or burning eyes and Loss of peripheral vision.
with Dr. Olatunji Idowu
Knee replacements I n the recent times I’ve encountered a lot of patients who have severe osteoarthritis of the knee and hip joints and who have been offered joint replacements; total hip and total knee joint replacements. These surgeries which had been in existence since the early seventies but which we have just perfected the art of doing it here in Nigeria always bring an element of fear, uncertainty or sometimes complete unbelief in our patients. I’ve therefore decided to do this piece in the hope that it will help allay the fears of our people towards joint replacements. What is a total knee replacement? A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material. The knee is a hinge joint which provides motion at the point where the thigh meets the lower leg. The thighbone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem. Depending on the condition of the kneecap portion of the knee joint, a plastic “button” may also be added under the kneecap surface. The artificial components of a total knee replacement are referred to as the prosthesis. The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backward in relation to the thigh-
bone. In total knee replacement surgery, this ligament is either retained, sacrificed, or substituted by a polyethylene post. Each of these various designs of total knee replacement has its benefits and risks. What patients should consider a total knee replacement? Total knee replacement surgery is considered for patients whose knee joints have been damaged by either progressive arthritis, trauma, or other rare destructive diseases of the joint. The most common reason for knee replacement in the United States and indeed here in Nigeria is severe osteoarthritis of the knees. Regardless of the cause of the damage to the joint, the resulting progressively increasing pain and stiffness and decreasing daily function lead the patient to consider total knee replacement. Decisions regarding whether or when to undergo knee replacement surgery are not easy. Patients should understand the risks as well as the benefits before making these decisions. There is also need to consider the cost of the surgery.
If you have any problem or question about your musculoskeletal system (bones, joints and muscles) do send me a mail at firstname.lastname@example.org for advice. Meanwhile, your comments and feedback on the issues discussed are highly welcomed.
Infected water, cause of cholera CONTINUED FROM PAGE 50 such as potable water for the citizens, especially the poor. “Cholera clearly has a direct link to lack of social amenities, including provision of good water sources. When these basic amenities are not being provided by the government of a nation, outbreaks of diseases quickly follow. Cholera is such a disease that is still prevalent because people are so poor in this country that the majority have shallow dug wells as their only source of water supply and some still use the pit toilet as the only place they excrete. Such places are fertile breeding grounds that can readily cause cholera epidemic to occur,’’ he lamented. The ailment is most likely to be found and spread in places with inadequate water treatment, poor sanitation and inad-
equate hygiene. Once persons are infected, they excrete the bacteria. Therefore, the infection can spread rapidly, particularly in areas where human waste is untreated. Dr Idris warns: “Cholera should be suspected in any person who develops diarrhoea with or without vomiting, weakness, restlessness, irritability, dry mucous membrane, low blood pressure, leg cramps, excessive loss of body fluids (dehydration) or dies from frequent stooling, hence adequate measures should be taken in order to reduce the risk of contracting the disease.” The commissioner urged members of the public to be vigilant and report any suspected case, dead or alive to the nearest health facility and the directorate of disease control in the state Ministry of Health. Dr Okanwa also warns people to be careful when eating food outside their homes
prepared by food vendors. “Most of these food sellers do not prepare their food in hygienic environments. Some even sell their food on top of open gutters and drainages. These are things that can easily breed the cholera virus and cause an outbreak. People should just be careful and identify a good place to eat,” he advised. Although there is a vaccine against cholera, WHO doesn’t normally recommend it because it may not protect up to half of the people who receive it and it lasts only a few months. However, you can protect yourself and family by using only water that has been boiled, chemically disinfected or bottled water and wash your hands frequently. Be sure to use the bottled, boiled or chemically disinfected water for the following purposes: drinking, preparing food, brushing
your teeth, washing of fruits, vegetables, dishes and cooking utensils. Idris advised members of the public to ensure they avoid possible backflow connection between water and sewer system and stressed the need to boil it before drinking when not sure of the source. He said mothers should also continue to breastfeed their babies having watery diarrhoea. “If you have been in contact with a cholera patient, wash your hands thoroughly after touching any item or surface that may have been contaminated and also dispose of contaminated items properly”, he added. He urged health workers to be on the alert and report suspected outbreaks of more than five cases in their facilities to the state Ministry of Health, stressing that people can also call the following numbers: 08023169485 or 0802321333, for assistance.