When choosing contact lenses, beginners often have many questions. In this article, we will consider what parameters should be considered when buying contact lenses for correcting myopia, hyperopia, astigmatism, and hyperopia. You will also find out what is the difference between soft and hard means of contact correction.
Every day, more and more people with refractive errors have preferred contact lenses. Unlike glasses, these optical products guarantee high definition not only central but also peripheral (side) vision. This allows you to fully enjoy the world and also eliminates excessive eye fatigue during operation. A person who first decided to buy contact correction means often has questions: how to choose the right product? how to start using them? how long does the adaptation period last? Only an ophthalmologist can answer them, and we suggest you read some useful recommendations.
There are certain rules for selecting contact lenses. Initially, a preliminary examination of the patient’s visual system is required. Based on the data received, the doctor determines what type of optical products you need and also writes out a prescription with the necessary indicators.
According to their purpose, lenses are divided into several categories. Spherical and aspherical models have been developed for people with myopia and farsightedness. Toric means of contact correction are used to correct astigmatism, and multifocal – to increase the clarity of vision with age-related farsightedness (presbyopia).
Depending on the material used in the manufacturing process, optical products can be soft and hard. The first ones provide maximum comfort during use due to the fact that they have increased elasticity. Modern soft lenses are made from hydrogel and silicone-hydrogel materials. Rigid optical products are usually used for severe vision deviations, for example, with a high degree of astigmatism, when soft ones are ineffective. Due to its higher stiffness, such optics retain their shape better and are firmly fixed during wearing.
All contact lenses are divided into:
Some patients mistakenly believe that it is possible to purchase means of contact vision correction only knowing the required diopters. However, this is far from the truth. There are a number of certain parameters that must be taken into account when buying ophthalmic products. The wrong choice of optics may not only cause uncomfortable sensations and reduce visual acuity but also adversely affect the health of the eyes. For example, lenses with a small radius of curvature squeeze the cornea, preventing the normal access of oxygen, which can lead to hypoxia. In turn, products with a too large radius will “hang out” in the eyes and cause unpleasant sensations.
The main criteria for choosing lenses:
An important role in using optical products is played by oxygen permeability (Dk / t) and moisture content (%). They directly depend on the material used in the manufacture of the lens, as well as a production technology. Soft contact optics can have a low (20-40%), optimal (40-60%) and high (60-90%) moisture content. The higher this indicator, the better since such correction tools contribute more to the hydration of the cornea, excluding dryness, burning and discomfort in the eyes. It is also recommended that optical products have an optimal oxygen permeability index. This will eliminate the risk of corneal hypoxia.
When buying contact lenses, you should also pay attention to the replacement schedule and wearing mode. One-day models are considered the safest and most comfortable. During the day, various deposits do not have time to accumulate on their surface. These optical products are suitable for people with dry keratitis, high sensitivity of the cornea and a tendency to allergies. They are indispensable for travel and business trips because they do not require care with a solution. Planned replacement lenses are on average cheaper than one-day ones. Moreover, these models need systematic cleaning and disinfection. Products designed for use within 1 month are very popular. They are the best choice in terms of price and quality.
Another significant parameter when buying contacts is wearing mode. Some models must be removed before bedtime, while others can be used at night, as well as continuously up to 7 and even 30 days. Ophthalmologists recommend removing and cleaning optics as often as possible. However, in some cases, for example, during long trips and business trips, this may be justified.
What to consider when choosing soft contact lenses?
In astigmatism, the lens or cornea is bent so that the refraction of the eye is slightly different in the horizontal and vertical planes. This leads to visual impairment and discomfort, such as headaches. Toric lenses are designed specifically for astigmatism correction. They have different optical powers vertically and horizontally, which allows for high definition image perception. One of them is aimed at correcting astigmatism, and the second is at correcting the concomitant refractive error. This is possible thanks to the special spherical cylinder design.
These ophthalmic products should always be positioned correctly on the eye. The selection of astigmatic contact lenses is extremely important because they have additional parameters: a cylinder that compensates for the distortion of the cornea or lens, as well as the middle axis, which keeps the line of sight clear. If the optical products are not selected correctly, the clarity of vision may be impaired. Therefore, you’d better entrust the selection of toric lenses to a professional.
People between the ages of 40-50 years often face presbyopia. They have difficulty reading text and looking at small objects at close range. The causes of age-related farsightedness have not yet been studied well, however, it is believed that over time, the characteristics of the eye muscles and lens change, which negatively affects the accuracy of perception of the picture. Previously, to correct presbyopia, people had to carry several pairs of glasses with them at once in order to focus at different distances: while reading, driving a car, etc. With the advent of multifocal lenses, everything became much easier. These optical products have a special design that allows you to clearly perceive the image at near, far and intermediate distances.
Types of lenses to correct presbyopia:
It is important that the selection of multifocal contact lenses is carried out by an ophthalmologist in accordance with the individual parameters of the patient’s vision. The specialist will choose the necessary model, taking into account the pupil width, the degree of vision deviation and the user’s lifestyle.
Rigid contact lenses are made of special gas-permeable materials, which, due to their higher elasticity, retain their shape and are firmly fixed before the eyes during operation. As a rule, they are recommended for use by patients with high degrees of myopia and hyperopia, as well as keratoconus and severe astigmatism, when it is not possible to correct visual impairment using soft models.
This product has a wider range of diopters. At the same time, it remains quite thin even with high optical power. The disadvantages include a longer adaptation period (up to 7 days) and selection difficulties associated with design features. It is important that the shape of the rigid lens is ideally suited to the shape of the cornea, as it fits as tightly as possible and fixes its position. In some cases, it’s possible to produce these products taking into account the individual parameters of the patient. It is important that the selection of hard contact lenses is done by an ophthalmologist after the examination.
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