Contact lenses

The number of wearers of contact lenses increases every year and wearing of contact lenses is safe if cerain rules are respected. Then they can be worn almost by everyone. Improving materials, which contact lenses are made from, also allow the wearing to people, who even did not dream of wearing of contact lenses a few years ago.

Opticians believe that permeability of contact lenses for oxygen is one of the main conditions for their successful application. Scientific studies agree that the number of adverse effects caused by chronical hypoxia (oxygen deficiency) of the cornea decreases with increasing oxygen permeability of contact lenses materials.

Contact lenses can be classified by the nature of the material from which they are made, by their wearing schedule, by their purpose, or by their design.

Before initiating any contact lens fitting for the purposes of optical correction, it is important to evaluate the patient`s motivation, ocular needs, and ocular and medical history. Unmotivated patients tend not to adhere to the prescribed methods and care regimens for the contacts, putting them at greater risk of complications.

The most common reason patients seek ophthalmic care is to optimize visual acuity. Estimates suggest that about 50 percent of the U.S. , Europe and Asia population utilize some form of refractive correction, and the natural history of presbyopia indicates that virtually everyone who lives long enough will benefit from optical correction.

The materials from which contact lenses are manufactured, has undergone great changes during development. So, how changed structure of contact lenses, depending on the acquisition of new knowledge on the anterior segment of the eye and the development of science requirements placed on flexibility, breathability, ease of production and others and compelled to finding progressive solutions to individual problems. A development of new advanced materials are still progressing forward, but not limited contact lens corneal metabolism found only in theoretical terms.

Contacts were made as great an invention of people's need to find an alternative to eyeglasses and time to improve on the excellent health supplement. Almost 40% of humanity needs a vision diopter adjustment, but now, with contact lenses, this percentage may be limited by anything, whether on the look, lifestyle or exercise.

Generally,  prescription contact lens represent a convex disc which is designed in the way that it perfectly overlaps a frontal transparent eye surface called the cornea. Thanks to the surface tension on the surface of contact lenses they perfectly adhere to the lachrymal film which covers the cornea. Prescription contact lenses help to guide a ray of light coming to the eye to the retina and because of that the image sharpens. To put it simply, contact lenses are medical tools which are used by people with certain visual disorder and which help them to improve their vision.

Because the contact lens is an optical device that is inserted directly into the eye and so there is contact with the cornea, it must meet strict criteria on the properties of the material from which are made. A contact lens must be safe for the eye and comfortable to wear. It is therefore placed considerable emphasis on the materials for their manufacture have the following excellent properties.

The functional benefits of contact lenses appreciate especially in areas such as sports, work in wet conditions and also in occupations and activities where eyeglasses can be very unpleasant, uncomfortable and interferes in many other cases. Contact lenses provide aesthetic benefits, they do not alter the appearance and semblance of the person who wears them.

Low and medium astigmatism the patient is able to partially correct by increased accommodation effort. However, this may lead ultimately to asthenopic difficulties, particularly where increased accommodation improves vision. In Children can then lead uncorrected astigmatism with axes inclined to the torticollis and scoliosis due to inclination of the head.

According to statistics, about 45% of future contact lens wearers have astigmatism 0.75 diopters or more. Percentage of toric contact lenses fitting is significantly lower. Astigmatism to 0,5 diopter is considered the most physiological and it is not needs to correct it. Also in this area, the requirements of patients on vision can vary significantly. We all know that sometimes improves visual acuity also cylinder 0.25 diopter in eyeglass correction.

Nowadays, soft contact lenses are most commonly used types of lenses. More than 90% of contacts wearers use soft contact lenses. This is mainly due to their perfect tolerability, simple handling, new material and still better price. In these days, soft contacts are able to correct almost any refractive error.

The difficulty of combining silicone rubber with a typical hydrogel-forming monomer was the first major obstacle in the development of the silicone hydrogel contact lenses. The first answer that springs to mind is to combine HEMA with TRIS, the monomer used in the preparation of RGP lens materials. However, combining hydrophobic TRIS with hydrophilic HEMA and then hydrating the product presents the same difficulty as trying to combine oil and water to form an optically clear product.

Hydrophilic gels are, in principle, polymers that contain a large percentage of water. Each macromolecule is combined in spatial lattice chemical bonds, which guarantee the dimensional stability and insolubility. Amount of hydrophylic monomers allow to create a range of gels with different properties.

Currently wearing hard contact lenses on the decline with the exception of the United States or Great Britain and Germany where are still used relatively often. Hard contacts are primarily indicated as therapeutic lenses in corneal diseases, such as keratoconus.

Extended wear contact lenses are type of contacts which allows their wearing a longer period of time without having removing from the eye at night  For many people the fact that they could each morning get up out of bed and do not insert your contact lenses in the eye very important. This is especially true if you are moderately or severely nearsighted, and you are not able to get without eyeglasses to the bathroom or kitchen.

Wearing daily disposable contact lenses has a couple of very significant advantages. If you are fed up with putting your contact lenses into a casing every evening, washing and cleaning them with the solution and then again in the morning taking them out of the casing, then daily disposable contact lenses are a simple answer. You put them on in the morning and in the evening, when you return home, there is nothing easier than taking them out of your eyes and throwing them away. You do not need any solutions or casing.

Color that is used in colored contact lenses, is actually a chemical that can be progressively released and can cause redness of the eye or worse, an allergic reaction. It also reduces the permeability of oxygen and thus leads to reduced corneal nutrition.

Hard contact lenses fitting to change the shape of the cornea deals orthokeratology. This method is used for short-sighted clients, using hard contact lenses. The contacts are worn at night, when they should have slightly modified the curvature of the cornea, during the day the clients are initially corrected by the normal way (lenses) until the shape of the cornea is correct. Conversion of the cornea is achieved by using special type of contact lenses, having inverted design. This process is reversible, which is a big advantage compared to alternative operational methods. His asset is also painless.