Tuesday, September 05, 2006

A Science Lesson in How Contacts Correct Vision Problems

A Science Lesson in How Contacts Correct Vision Problems

Contact lenses have become an increasingly popular alternative to glasses for correction of visual problems. With their ease of use and their ever-increasing level of comfort, it is easy to see why so many people have turned to contact lenses to help them see. In addition, most people find themselves to be more attractive looking when wearing contact lenses and prefer to wear them while engaging in sports. But, how exactly do contact lenses help improve site and what are the differences between the many types available?

The Miracle of Contact Lenses

For those individuals with visual problems, there is a problem between the length of their eye and its refractive power. As a result, the eye experiences a refractive error. A refractive error is a problem in which the eye fails to focus light properly. As a result, the person has decreased visual acuity, or the ability to see clearly. The contact lens helps correct this problem by focusing the light properly onto the retina. As a result, contact lenses are capable of correcting the vision of those with myopia (near sightedness), hypermetropia (far sightedness), presbyopia, and astigmatism.

More specifically, a person will experience “perfect vision” when rays of light are capable of meeting at a point directly on the retina, which is located on the back of the eyeball. Unfortunately, only about 40% of people have eyes that successfully perform this task. For the remaining 60%, proper vision must be achieved by refocusing the light within the eye.

Contact lenses, which are held in place by the natural tears created by the eye, form a thin layer over the eye to assist with refocusing. For those who have myopia, the problem is with seeing objects at a distance. The contact lenses prescribed to patients with myopia, therefore, are concave. This helps to properly refocus the light onto the retina. A patient with hyperopia, on the other hand, has difficulty seeing objects close up. Therefore, convex contact lenses are used to help redirect the light in their eyes.

For those with astigmatism, the problem is a little different. An irregularly shaped cornea characterizes astigmatism. Therefore, the light entering the eye is focused on two separate points within the eye. Originally, contact lenses were unable to assist those with astigmatism at achieving better vision. New “toric” lenses, however, have been developed to help improve the vision of those with astigmatism, as well.

Toric lenses are different from traditional spherical contact lenses, which have the same power of correction throughout the lens. A toric contact lens, on the other hand, has varying powers of correction throughout the lens. These special contact lenses actually have two different powers to them and are designed to stay in place regardless of eye movement. In fact, they are often weighted in an area to help keep them in place. Some have tiny marks on them to help the wearer determine the proper way to place them in the eye while others are designed to reset themselves properly when the wearer blinks.

Presbyopia, which is the natural aging of the eye and resulting loss of sight, makes it difficult for the patient to shift from viewing far objects and near objects. This condition also makes it difficult for patients to read. Amazingly, bifocal contact lenses are now available for those with presbyopia, making it possible for them to be free from wearing glasses, as well.

Choosing the Contact Lenses that are Right for You

With so many advancements in contact lens technology, it can be easy for a person to become confused by the multitude of choices available. Two forms of contact lenses currently available are daily wear contact lenses and extended wear contact lenses.

The wearer should take out daily wear contact lenses each night before going to bed. Extended wear contact lenses, on the other hand, can be worn overnight. In fact, they can often be worn for six or more nights in a row. Some of the newest types of contact lenses can even be worn for up to 30 nights in a row, though these are generally referred to as continuous wear contact lenses. The reason these contact lenses can be worn for such great lengths of time is because they are oxygen permeable, which is a great step in the right direction for contact lenses because it helps keep the eye healthy.

Christmas tree Care Tips

Christmas tree Care Tips

Every year, there is always that office party, neighborhood get-together, or family reunion that brings everyone together, whether they like it or not, to the same place. And in that same place there is the one Christmas tree which everybody is supposed to admire and compliment. The problem comes when you’re the one who’s hosting the party and needs to get a tree up and decorated as soon as possible, while you’re running around with a turkey and a string of other things to do.

The first thing to do is to go out and buy your tree. There is a reason the old carpenters phrase ‘measure twice, cut once’ is still well-used and this is one of them. A tree that is obviously too short or too wide will look out of place, and that’s not what you want for your grand holiday event. If you decide to go for a real tree rather than plastic, then there’s always the risk of some not-so-pretty spots. Before getting your money out, double check that there are no gaps or clusters of branches. If there is one or two on one side, then you can always face them towards a wall but it’s something to be aware of.

Some trees are easier to decorate than others too. The shorter the needles, the easier it will be. Whichever tree you decide to get, make sure you either have a sturdy stand for it at home, or can get one in time. For larger trees, the diameter of the base will be bigger and you’ll need to work that in while considering your tree stand. Most importantly, your Christmas tree should be fresh and young. You can tell if a tree is fresh by feeling the leaves or needles. They should be bright and all the same shade of green. They should not fall off while touching them. If they fall off, look a touch on the brown side, or seem dry and pokey, then most likely, the tree won’t last for your party or look half as good at it.

If your tree has sharp little needles on it, you’ll need to be prepared for that too. They have a habit of falling off onto the floor if they get brushed up against one too many times, or are starting to get older.

The location of your Christmas tree will play a big role too. Stay away from fireplaces, windows, or vents, that could circulate heat and raise the risk of a fire—the ultimate party-douser. Make sure to stay away from frequently populated areas like in the middle of the room or by a doorway. Decorations could get knocked or brushed off, and it can greatly lower the significance of your beautiful, seasonal tree.

Once you have your tree at home—but not in place—double check everything. If there are any branches that aren’t quite at the same level or angle as the others, don’t hesitate to chop it around until it meets your standards. Don’t go crazy with the saw or anything, but you paid your money, you can do whatever you like with it, including shaping or molding it to ‘perfection’.

In the end, your Christmas tree might last a few weeks, but your flooring will (well, we can hope) last much, much longer, so when it comes to moving your tree into your home, put down large, plastic garbage bags, or old sheets in case someone drops the tree while moving it, or any needles fall off on the way. More to the point, it is a live tree and there will be bugs. They show up easier on a white sheet then they do on hardwood flooring.

Once your tree is in place, with its tree stand supporting it, you might consider other forms of support. You can get another base to aid the stand, or, depending on the height and place of the room, consider tying the top of the tree with a clear string to the ceiling. One of the worst things that can happen is having your decorated tree fall flat on the floor—or worse, onto a guest—and having to re-do it then.

You can buy or make cover sheets for the bottom of your tree too, to finalize the decoration and cover up the tree stand. Decorating the tree is the most fun of the entire experience. You can check the Internet for ideas on homemade ornaments and themed trees that will draw the eye that much more.