contact lenses

Contact lenses usually serve the same corrective purpose as conventional glasses, but are lightweight and virtually invisible — many commercial lenses are tinted a faint blue to make them more visible when immersed in cleaning and storage solutions.

Contact lenses are less affected by wet weather, do not steam up, and provide a wider field of vision. Contact lenses are classified in many different manners. Contact lenses are typically inserted into the eye by placing them on the index finger with the concave side upward and raising them to touch the cornea. Contact lenses are one option for correction ofmyopia, hyperopia, astigmatism and presbyopia.

People choose to wear contact lenses for various reasons. Many consider their appearance to be more attractive with contact lenses than with glasses. 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.

Conditions correctable with contact lenses include near (or short) sightedness (myopia), far (or long) sightedness (hypermetropia), astigmatism and presbyopia. In the United States, the FDA frequently calls non-corrective cosmetic contact lenses decorative contact lenses. Theatrical contact lenses are a type of cosmetic contact lens that are used primarily in the entertainment industry to make the eye appear pleasing, unusual or unnatural in appearance, most often in horror and zombie movies, where lenses can make one's eyes appear demonic, cloudy and lifeless, or even to make the pupils of the wearer appear dilated to simulate the natural appearance of the pupils under the influence of various illicit drugs.

Contact lenses that deliver drugs to the eye have also been developed. The first contact lenses were made of glass, which caused eye irritation, and were not wearable for extended periods of time. An alternative technique is piggybacking of contact lenses, a smaller, rigid lens being mounted atop a larger, soft lens. Extended- and continuous-wear contact lenses 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. The various soft contact lenses available are often categorized by their replacement schedule. More commonly, contact lenses are prescribed to be disposed of on a two-week or monthly basis. Myopic (nearsighted) and hypermetropic (farsighted) people who also have astigmatism and who have been told they are not suitable for regular contact lenses may be able to use toric lenses. Toric lenses are made from the same materials as regular contact lenses but have a few extra characteristics:They correct for both spherical and cylindrical aberration. Like eyeglasses, contact lenses can have one (single vision) or more (multifocal) focal points. Multifocal soft contact lenses are more complex to manufacture and require more skill to fit. All soft bifocal contact lenses are considered "simultaneous vision" because both far and near vision corrections are presented simultaneously to the retina, regardless of the position of the eye. Intraocular lenses, also known as an implantable contact lenses, are special small corrective lenses surgically implanted in the eye's posterior chamber behind the iris and in front of the lens to correct higher degrees of myopia and hyperopia. Although many companies make contact lenses, there are four major manufacturers: Vistakon/Johnson & Johnson, CIBA Vision, Bausch & Lomb, and CooperVision.

The prescribing of contact lenses is usually restricted to appropriately qualified eye care practitioners. In countries such as the United States (where all contact lenses are deemed to be medical devices by the Food and Drug Administration), the United Kingdom and Australia, optometrists are usually responsible. In other parts of the world, opticians usually prescribe contact lenses. Prescriptions for contact lenses and glasses may be similar, but are not interchangeable. Have youreyes examined regularly and always follow your eye care professional's instructions forthe proper use and care of your contact lenses. Whether you already wear contact lenses or are considering them, this section serves as a primer. Facts and statistics about contact lens wearers, pointers for safe and successful use of contact lenses, and contact lenses and cosmetics are just a few of the topics covered here. Getting started right with your contact lenses involves going to a doctor who provides full-service care. Carefully and regularly clean contact lenses, as directed by your optometrist. Daily disposable contact lenses are the ideal for people with allergies. You can buy contact lenses only if you have a current, valid prescription.

Contact Lenses