Today, there are many ways to correct vision. Very often, contact lenses are used to improve its severity and eliminate other problems. Depending on the type of material, soft and hard gas permeable contact lenses are distinguished. Of course, the first type is most often used, however, the latter have many advantages.
Hard Lens Materials
Hard lenses became widespread at the end of the twentieth century. Then the main material for their manufacture was polymethyl methacrylate. The lens itself was relatively small. The disadvantage of such lenses was the lack of gas exchange. Access of oxygen to the cornea was carried out only due to the mobility and small size of such a correction tool. However, today more modern and high-quality materials are used. Rigid gas permeable contact lenses are made from fluorine-silicone compounds. Due to this, the lenses have good oxygen permeability. It is worth noting that they are quite comfortable, make them individually, make an exact fit for a particular patient.
Indications for the use of hard lenses
Soft contact lenses have limitations in the range of optical power. Often they are prescribed for myopia up to -12 diopters, myopia is not higher than 8 diopters. A stronger degree of myopia requires specific correction. Soft lenses with high optical power will in this case have a considerable thickness. This, in turn, increases the risk of complications (a tight fit can lead to eye hypoxia). You can, of course, use glasses, but today experts offer modern rigid gas-permeable contact lenses. They have a wide range of refraction - from -25 diopters to +25 units. The use of modern material provides a sufficient supply of oxygen to the eye. Moreover, the thickness of such lenses is not much different from the corresponding parameters of soft products for vision correction.
Hard lens design
Modern hard lenses have an optical zone, which is located in the center of the product. Its diameter does not exceed 8 mm. Thanks to the slip zone, which has a specific structure, the lens is firmly fixed to the eyeball. The smallest size is the edge region. It is she who is responsible for the comfortable wearing of the product, ensures the normal exchange of tear fluid under the lens.
The main advantages of these lenses
Many patients note that hard gas-permeable hard lenses are less prone to deformation, creasing. Due to the fact that their diameter is slightly smaller than that of soft lenses, such products leave the peripheral zone of the cornea open. This, in turn, does not violate the tear exchange process. They are also more resistant to protein deposits, so the period of safe operation increases. Since water is completely absent in the composition, hard lenses cannot dry out, the patient does not need to use special moisturizing drops. It is important to note their profitability: the indication for replacement is only a change in visual acuity. With astigmatism, hard contact lenses are also shown . Patient reviews indicate that correction with soft lenses in this case is rather difficult, the only option is the use of hard products. Orthokeratological correction is also widespread. It involves the use of hard lenses only at night.
Orthokeratology. What is the essence of the methodology
This type of vision correction allows you to maintain its sharpness in the daytime, at night it is necessary to wear special lenses. In the process of sleep, the cornea of the eye changes, its optical zone becomes more flat. This form is saved all the next day. As a rule, the effect of such correction can last two days. Night lenses are good for children, patients with a progressive form of myopia, if there are contraindications for the operation to restore vision. Also, this method is often chosen by people of certain professions: athletes, military, builders, etc. Contraindications to orthokeratological therapy are diseases of the cornea of the eye, eyelids, all kinds of inflammatory processes, dry eye syndrome.
The negative aspects of using hard lenses
In addition to the above advantages, hard lenses have their drawbacks. First of all, a certain adaptation period is needed (about a week). After getting used to it, the discomfort disappears, but even a short break in wearing requires a new getting used to the products. Some degree of corneal deformity is observed if rigid gas permeable contact lenses have been used. Testimonials of patients indicate that the use of glasses after such lenses does not bring the desired result: the image becomes blurry, the sharpness decreases. However, this is a temporary effect. After the restoration of the cornea, you can safely use glasses without losing the quality of vision. Also, the process of selecting products is quite lengthy, their initial cost will also be an order of magnitude higher than that of soft lenses.
How to choose the right gas permeable lenses
In order to correctly choose hard lenses, first of all, you need to contact a specialist. It determines visual acuity, the maximum degree of correction. Using special equipment, the ophthalmologist measures the necessary parameters of the cornea of the patient. The following is the fitting of several pairs. All these manipulations are necessary for a perfect fit of the lens. The manufacture of hard contact lenses is carried out purely individually, with more than 20 parameters of the eye taken into account. An engineer models the required design (optical zone, slip zone, edge region). Then, on a special machine, the product is machined in full accordance with the layout. The most famous manufacturer in this area is the German company Wohlk. This manufacturer provides high quality products. As a rule, after 14 days you can get a ready-made set of lenses.
Daily care for hard contact lenses
First of all, any lenses require personal hygiene. Before removing or donning, hands should be washed with soap. It is best to wipe them with a waffle towel to avoid getting various fibers on the lens. Storage containers should be kept clean. There are special rules for women. Makeup should be applied only after the lens is dressed. Accordingly, and remove it after removing the product from the eye. A daily cleaner for hard gas permeable contact lenses is also needed. With its help, pollution, tear fluid are removed . Once a week, a deeper cleaning is carried out. It is worth noting that lenses can not be rubbed strongly so as not to violate the optical properties. Today, a multifunctional cleaner for hard contact lenses is widespread. It allows you to effectively remove protein deposits (for example, a solution of Boston Simplus), does not require additional enzymatic purification. It also excellently disinfects and softens the contact lens. Over time, the product is more difficult to clean. In this case, hard lenses can be polished in a special laboratory.
Special requirements for hard lens wearers
Wearing hard lenses imposes certain responsibilities on the patient. Ophthalmologist visits should be regular. This will enable the specialist to assess the condition of the eyes. At the slightest change in the condition of the eyes, it is necessary to consult a specialist. Timely treatment will help to avoid conditions such as corneal edema, microbial keratitis, conjunctivitis, corneal ulcer, allergic reactions. Rigid gas permeable contact lenses are an excellent tool for correcting vision in many cases, but they require proper and thorough care.