CONTACT LENS

HISTORY Leonardo da vinci is frequently credited with introducing the general principle of contact lenses in his 1508 Codex of the eye, Manual D, where he described a method of directly altering corneal power by submerging the eye in a bowl of water. Leonardo, however, did not suggest his idea be used for correcting vision—he was more interested in learning about the mechanisms of accommodation of the eye .In 1801, while conducting experiments concerning the mechanisms of accommodation, scientist Thomas Young constructed a liquid-filled "eyecup" which could be considered a predecessor to the contact lens. On theeyecup base, Young fitted a microscope eyepiece. However, like Leonardo's, Young's device was not intended to correct refraction errors.In 1999, an important development was the launch of the first silicone hydrogels onto the market. These new materials encapsulated the benefits of silicone—which has extremely high oxygen permeobility—with the comfort and clinical performance of the conventional hydrogels which had been used for the previous 30 years. These lenses were initially advocated primarily for extended (overnight) wear although more recently, daily (no overnight) wear silicone hydrogels have been launched.

A contact lens (also known simply as a contact) is a corrective,cosmetic, or therapeutic lens usually placed on the cornea of the eye. Modern soft contact lenses were invented by the Czech chemists otto wichterle andDrahoslav lim, who also invented the first gel used for their production.

Corrective contact lenses

A corrective contact lens is a lens designed to improve vision. In many people, there is a mismatch between the refractive power of the eye and the length of the eye, leading to a refraction error. A contact lens neutralizes this mismatch and allows for correct focusing of light onto the retina. Conditions correctable with contact lenses include near (or short) sightedness (myopia), far (or long) sightedness (hypermetropia), astigmatism and presbyopia. wearers must usually take their contact lenses out every night or every few days, depending on the brand and style of the contact. Recently there has been renewed interest in orthokeratology, the correction of myopia by deliberate overnight flattening of the cornea, leaving the eye without contact lens or eyeglasses correction during the day.

For those with certain color deficiencies, a red-tinted "X-Chrom"contact lens may be used. Although the lens does not restore normal color vision, it allows some colorblind individuals to distinguish colors better.A cosmetic contact lens is designed to change the appearance of the eye. These lenses may also correct the vision, but some blurring or obstruction of vision may occur as a result of the color or design. In the United States, the FDA frequently calls non-corrective cosmetic contact lenses decorativ.

By wear time

A daily wear contact lens is designed to be removed prior to sleeping. An extended wear (EW) contact lens is designed for continuous overnight wear, typically for 6 or more consecutive nights. Newer materials, such as silicone hydrogels, allow for even longer wear periods of up to 30 consecutive nights; these longer-wear lenses are often referred to as continuous wear (CW). Generally, extended wear lenses are discarded after the specified length of time. These are increasing in popularity, due to their obvious convenience. Extended- and continuous-wear contactlenses can be worn for such long periods of time because of their high oxygen permeability (typically 5-6 times greater than conventional soft lenses), which allows the eye to remain healthy.

Extended lens wearers may have an increased risk for corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability, and bacterial stagnation. corneal neovascularization has historically also been a common complication of extended lens wear, though this does not appear to be a problem with silicone hydrogel extended wear. The most common complication of extended lens use is conjunctivitis, usually allergic orgiant papillary conjunetiv.

Complications

complications due to contact lenswear affect roughly 4% of contact lens wearers each year.^[40] Excessive wear of contact lenses, particularly overnight wear, is associated with most of the safety concerns.^[2] Problems associated with contact lens wear may affect the eyelid, the conjunctive, the various layers of the cornea, and even the tear film that covers the outer surface of the eye.

Studies conducted on side effects from long-term wearing of contact lenses, i.e. over 5 years, such as by Zuguo Liu PhD, MD and Stephen C. Pflugfelder MD: "The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity", Ophthalmology , Volume 107 , Issue 1 , Pages 105 - 111, concludes that: Long-term contact lens wear appears to decrease the entire corneal thickness and increase the corneal curvature and surface irregularity.

Usage

Before touching the contact lens or one's eyes, it is important to thoroughly wash and rins hand with a soap that does not contain moisturzers or allergens such as fragrances. The soap should not beantibacterial due to risk of improper hand washing and the possibility of destroying the natural bacteria found on the eye. These bacteria keep pathogenic bacteria from colonizing the cornea. The technique for removing or inserting a contact lens varies slightly depending upon whether the lens is soft or rigid.

Studies conducted on side effects from long-term wearing of contact lenses, i.e. over 5 years, such as by Zuguo Liu PhD, MD and Stephen C. Pflugfelder MD: "The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity", Ophthalmology , Volume 107 , Issue 1 , Pages 105 - 111, concludes that: Long-term contact lens wear appears to decrease the entire corneal thickness and increase the corneal curvature and surface irregularity.

Care

Lens cover to store contact lens

While daily disposable lenses require no cleaning, other types require regular cleaning and disinfecting in order to retain clear vision and prevent discomfort and infections by various microorganisms including bacteria, fungi, and Acomthamoeba, that form abiofilm on the lens surface. There are a number of products that can be used to perform these tasks:

WATCHES

A watch is atimepice that is made to be worn on a person. The term now usually refers to a wristwatch, which is worn on the wrist with a strap or bracelat . In addition to the time modern watches often display the day, date, month and year, and electronic watches may have many other functions.

Most inexpensive and medium-priced watches used mainly for timekeeping are electronic watches with quartz movements. Expensive, collectible watches valued more for their workmanship and aesthetic appeal than for simple timekeeping, often have purely mechanical movements and are powered by springs, even though mechanical movements are less accurate than more affordable quartz movements.

A movement in watchmaking is the mechanism that measures the passage of time and displays the current time (and possibly other information including date, month and day). Movements may be entirely mechanical, entirely electronic (potentially with no moving parts), or a blend of the two. Most watches intended mainly for timekeeping today have electronic movements, with mechanical hands on the face of the watch indicating the time.Some electronic watches are also powered by the movement of the wearer of the watch. Kinetic powerd quartz watches make use of the motion of the wearer's arm turning a rotating weight, which turns a generator to supply power to charge a rechargeable battery that runs the watch. The concept is similar to that of self-winding spring movements, except that electrical power is generated instead of mechanical spring tension.solar powered watches are powered by light. A photovoltic cell on the face (dial) of the watch converts light to electricity, which in turn is used to charge a rechargeable battery or capacitor. The movement of the watch draws its power from the rechargable battery or capacitor. As long as the watch is regularly exposed to fairly strong light (such as sunlight), it never needs battery replacement, and some models need only a few minutes of sunlight to provide weeks of energy.Since the advent of electronic watches that incorporate small computers, digital displays have also been available. A digital display simply shows the time as a number, e.g., 12:40 AM instead of a short hand pointing towards the number 12 and a long hand pointing towards the number 8 on a dial.All watches provide the time of day, giving at least the hour and minute, and usually the second. Most also provide the current date, and often the day of the week as well. However, many watches also provide a great deal of information beyond the basics of time and date. Some watches include alarms.Wristwatches are often treated as jewelry or as collectible works of art rather than as timepieces. This has created several different markets for wristwatches, ranging from very inexpensive but accurate watches intended for no other purpose than telling the correct time, to extremely expensive watches that serve mainly as personal adornment or as examples of high achievement in miniaturization and precision mechanical engineering.

FAMILY JEWELRY

Pearl necklace is one of the best gifts to your girl friend, your wife or any women who wants to impress. Pearl necklaces are often a family heirloom, and many brides wear them on their wedding days. As we know, the size and color affect the price. Except pearl size and pearl color, luster, Nacre thickness and Shape are the factors affect the price too. More bigger, more expensive. So when you want to choose a pearl necklace as a gift, you need to look at several factors: Which color and shape of pearl necklace you prefer Which type of pearl necklace that you want to purcha.Perhaps some of the most intimate pieces of jewelry are gold lockets. They’re at the same level as wedding bands, engagement rings, and family hairlooms. After all, there are no other kinds of jewelry that are more suited for carrying your loved ones closest to your heart—both literally and figuratively—than gold lockets. Gold lockets are very special in three ways—the metal with which they are made is precious; they’re usually beautifully done; and lastly, they can be personalized with engraving and pictures. Gold lockets are more than pieces of jewelry that are worn for adornment; they’.Many people, especially women love to wear all sorts of accessories to accentuate their clothing and appearance. One of woman’s prized possessions is her jewelries. There are many kinds of jewelry and one of the most popular trends nowadays is photo jewelry. What is it anyway? Photo jewelry is having your photo or an image inserted in the pendant as part of the design. You can give it to your friends or family to have a customized appeal. Many people have preferred photo jewelry these days because aside from its unique appearance.Popularity of personalized jewelry is increasing day by day. Nowadays people are being more and more fashion oriented and open to experiment with their looks and style. This changing attitude of people is one of the helping factors in increasing popularity of personalized jewelry. Although personalized jewelry products have been used in various aspects, but the most important and popular use of personalized jewelry products is as gifts on various occasions.

HAIRPINS

A hair pin or hairpin is a long device used to hold a person's hair in place.

Hairpins made of metal, ivory, bronze, carved wood, etc. were used in ancient Assyria and Egypt for securing decorated hairstyles Such hairpins suggest, as graves show, that many were luxury objects among the Egyptians and later Greeks, Etruscans, and Romans. Major success came in 1901 with the invention of the spiral hairpin by NewZealand inveontor Ernet Godward. This was a predecessor of the hair clip.

The hairpin may be needle-like and encrusted with jewels and ornaments. It often may be more utiliarain—designed to be almost invisible after being inserted into the hairstyle.

Hairpins also may be constructed from different lengths of wire that are bent in half with a u-shaped end and a few kinks along the two opposite portions. The finished pin may vary from two to six inches in final length. The length of the wires enables placement in several styles of hairdos to hold the style in place. The kinks enable retaining the pin during normal movements.

RINGS

Mankind has believed in the special powers and capabilities of gemstones since many centuries. Gemstones were earlier worn as simple pendants or amulets and supposed to protect the person wearing them from evil forces.

The first rings that were made did not have any gemstones at all. These were silver, gold or copper rings in a flat or rounded style. Gemstone rings gradually evolved and the beliefs in the powers of gemstones spread to rings with gemstones too. Gemstone rings made with these beliefs are common even today. Here are a few popular types of gemstonerings that can be found today.

(1) Birthstone Rings: It is believed that there is a gemstone that represents every month in the year and is thus related to a zodiac sign. Gemstone rings with a birthstone are supposed to bring good luck and ward off evil. Gemstone rings worn as birthstone rings are usually made with a single gemstone.

(2) Anniversary Rings: Similar to birthstones, anniversary rings are made for each year of marriage. The second year of marriage is represented by the garnet gemstone, the tenth year by a diamond ring and so on. Anniversary gem stone rings are a bit more fancy and normally include a few small diamonds to add glitter to the ring too.

(3) Family Birthstone Rings: These are a special category of gemstone rings where, each ring has the birthstone of all the members of the family. These would be a type of multi-gemstone ring. In cases where members of a family are spread in geographically far off places, family birth stone rings provide a kind of spiritual bonding.

(4) Multi Gemstone Rings: As mentioned above, family birthstone rings are a kind of multi gemstonerings. There are other reasons why people make rings with multiple gemstones, it is believed that a combination of gemstones with special powers in the same ring, increases the effectiveness of the gemstones. A simpler reason is that, gemstones rings with multiple gemstones can match with a variety of colored garments.

(5) Wedding and Engagement Rings: The engagement ring is almost always a gemstone ring with diamonds adding accent to it. Made on a comparatively higher budget, gemstone rings for engagements use gemstones like rubies, sapphires, emeralds etc. Wedding rings are made as gemstone rings in a few countries, however most people prefer simple gold or silver bands for wedding rings. The more exotic gemstone rings are created as engagement rings.

(6) Religious and Mythological Rings: A classic example of such a gemstone ring is the 'navratan' ring that is prominent in Hindu mythology. The ring comprises of 9 gemstones, each with a special power of it's own. Thai mythology also has a gemstone ring called the 'nok-phak-kow' ring that has 9 gemstones.

(7) Historical Jewels: The ring that immediately comes to mind is the Claddagh ring with a rich cultural heritage and a legend that dates back to over 300 years. This Irish ring was first made without any gemstone, but designs evolved that combined birthstones with the Claddagh ring.

NEEKLACES

A necklace is an article of jewelery which is worn around the neck. Necklaces are frequently formed from ametal chain, often attached to a locket or pendat. Necklaces can also be manufactured with cloth, and they sometimes contain rocks (particularly gems), wood, and/or shells with different shapes and sizes.

Necklace have been worn throughout history, by both men and women, and have been used as marks of distinction in many cultures, including the ancient Hebrew culture.Necklaces, handsome and richly ornamented, were a principal part of the dress, both of men and women, among the ancient Egyptians; and some idea of the number of jewels they wore (remarks Sir G. Wilkinson) may be formed from those borrowed by the Is raelites at the time of the Exodus, and by the paintings of Thebes. They consisted of gold or of beads, of various qualities and shapes, disposed according to fancy and enriched with jewels.

Necklaces of gold thickly set with gems were worn by the Greeks and Romans of both sexes. There was a famous necklace of the most costly precious stones upon the statue of Vesta in Rome, to whose vengeance Zosimus attributes the tragic end of Serena, Stilicho's widow, who had despoiled her of it. By the command of Honorius she was strangled.

The necklace taken from the neck of the Hindu King Jaipal, captured by Mahmud (A.D. 1001) was composed of large pearls, rubies, etc., and was valued at two hundred thousand dinars, or a good deal more than a hundred thousand pounds.

Homer mentions a necklace curiously wrought of gold interwined with amber, which Eurymachus presented to Penelope.

EARRINGS

you can save money by buying lower quality cuts, because it is a feature that few nonprofessionals will notice. You can also try to by less common cuts because they are usually the most affordable diamond earrings. Princess cut diamonds are usually 30% more expensive than emerald cuts, making emerald diamond earring the more affordable diamond earrings.

The color is the natural tint of the diamonds. Diamonds occur naturally in nature and therefore do not always come clear. If you buy diamonds with a little bit of a yellow tint than it is much easier to find affordable diamond earrings Conversely, diamonds full of natural color like pink and red are more expensive and should be avoided when trying to buy affordable diamond earrings.

Clarity is the number of inclusions or imperfections in your diamond earrings Diamonds come from nature with small gas pockets these pockets reflect the light differently than the rest of the diamond. A perfectly clear diamond is very expensive so when looking to buy affordable diamond earrings a few marks inside are perfectly acceptable. Usually these marks are difficult even impossible to see by the naked eye, so they make a great way to get cheaper diamond earrings

Carat is the size of a diamond. A carat is about 200 milligrams, and each carat is broken up into 100 "points". When buying diamonds from a reputable dealer make sure you know the difference between a carat and a point. If you see a deal that is .25 for less than $100 than it is most likely .25 points or not real diamonds. A reputable retailer will be honest with you about the size and will always write ct (the symbol for carat) or ctw/tcw (the symbols for total carat weight). When buying diamond earrings, look for the total carat weight symbol because earrings come in pairs and should have two equal size dianite earrings help you portray and elegant, yet simplistic look when you wear this type of earrings in your ears. Moissanite is not really an imitation diamond, but occurs naturally in nature. Unlike earringscontaining cubic zirconia diamonds, the moissanite earrings contain a stone that is very close to the diamond in appearance and hardness.

You can choose moissanite earrings that dangle from your ears or moissanite stud earrings. Moissanite is very popular in jewellery, especially rings and earrings, because it is very durable. It is resistant to heat, which makes it more brilliant than diamonds. You can have the moissanite cut in the same cuts as diamonds, but it produces sharper facets. This enables it to catch the light and reflect better.

When you wear moissanite earrings, whether they are moissanite stud earrings are hang to your shoulders, every time you turn your head the stones will glisten. It is the perfect alternative to diamonds in stud earrings and it is much cheaper. This fact enables you to have many different styles of these earrings containing moissanite, so you can wear a different pair to each occasion.

Although the color of moissanite earrings falls within the range of I -K color range of diamonds, two fancy varieties of moissanite have been developed. Now you can have moissanite stud earrings in blue, resembling blue diamonds and green, which looks somewhat like tsavorite - a new gemstone discovered in Kenya in the 1960's. Because of the high cost of colored diamonds, earrings with moissanite in one of these colors will make a big splash without costing you a fortune.

When getting moissanite stones cut for earrings, you need to have the stone cut with optic axis perpendicular to the table of the stone. This will minimize the appearance of the stone in moissanite earrings so one cannot tell immediately that it is not a real diamond. With the small stone used in moissanite stud earrings, it is very difficult for an untrained eye to tell the difference.

The dispersive power of moissanite earrings is more than double that of diamonds. While some people feel that this property is really elegant in moissanite earrings, others feel it is a little too much. You really need to compare the moissanite stud earrings to stud earrings containing a diamond and see for yourself if it is what you want. amonds.