Recently, the number of contact lens users has been growing, in which there is a decrease in visual acuity, associated precisely with improper selection and neglect of the contact lens.
How can you wear contact lenses so as not to harm your eye?
Contact lenses, according to statistics, are used by more than 100 million people in the world. Unfortunately, some people in principle cannot afford to use them. This can happen due to allergies, dry eyes, or due to the poor fit of the lens in the eye if the radius of curvature does not correspond to the shape of the cornea.
Classification
Contact lenses are lenses that are applied directly to the mucous membrane of the eye. They are made from various types of transparent materials and have a small size. They are intended to increase visual acuity. Correction of vision using contact lenses is called contact vision correction. Colored contact and tinted lenses are also available (they are also called cosmetic) and decorative, which serve as an ornament to the eye. They are also able to correct vision.
Contact lenses are classified according to certain criteria:
- The material they are made of
- Replacement frequency
- Wearing mode (continuous, prolonged, daily, flexible),
- Design (spherical, aspherical, toric, multifocal),
- Degree of transparency (transparent, color and tint, decorative).
According to the material, contact lenses are divided into:
- soft lens
- hard lens
About 90% of people all over the world use mostly soft contact lenses, which are also divided into 2 types:
- hydrogel
- silicone hydrogel
In hydrogel contact lenses, oxygenation of the cornea of the eye depends on how much water there is in them.
Moisture, of course, favorably affects the condition of the eye, but the problem is that with an increase in the amount of water, hydrogel lenses become too soft, which makes it difficult to use. The maximum allowable amount of water in hydrogel lenses is 70%. For this reason, it is better to give preference to silicone-hydrogel, since in these lenses oxygen saturation does not depend on the volume of water in them.
Hard contact lenses are used, as a rule, in difficult situations, for example, with a high degree of astigmatism. They increase visual acuity due to the fact that they retain their shape.
The frequency of replacement is the maximum period of use of contact lenses, after which they must be replaced with new ones. Manufacturers may recommend replacing them once in :
- Day (one day)
- 1 – 2 weeks
- Month (monthly replacement),
- 3 and 6 months
- Year (traditional).
Wear mode is the maximum period of use during which, without removing, you can wear contact lenses. It can be:
- Continuous (the lenses are worn and are in front of the eyes all night for 30 days, but this mode is allowed by the manufacturers only for certain types of silicone-hydrogel lenses and is not suitable for everyone because of the individual characteristics of the eyes),
- Prolonged (lenses are used throughout the week and remain on the eyes throughout the night)
- Daytime (in the morning the lenses are worn over the eyes, worn all day, and removed before going to bed),
- Flexible (lenses are worn without taking off, 1 – 2 days).
Depending on the pathological condition of the eyes, contact lenses are selected that differ in design, for example:
- Spherical (correction of myopia and hyperopia)
- Toric (correction of myopia and hyperopia with existing astigmatism)
- Multifocal (correction of presbyopia)
- Aspherical (guarantee a higher quality of vision, which is achieved using a low percentage of distortions characteristic of spherical lenses).
The degree of transparency distinguishes lenses:
- Transparent
- Color and tint
Clear contact lenses are a classic option.
Color and tint, as well as decorative, are designed for aesthetic beauty. The latter can be with or without diopters.
All types of contact lenses can be used in any weather. But there are also restrictions for them. For example, with any stay inside the water, you can only use lenses in case you use swimming goggles or a mask.
While using a lens, you should not visit the sauna and bath. It is necessary to remove them when in contact with irritating vapors and gases. Otherwise, they must be replaced with a new pair. As for cosmetic and decorative lenses, it is not recommended to use them in the dark and when driving.
At present, there is special equipment with which ophthalmologists conduct eye diagnostics, on the basis of which contact lenses are selected for the patient. When selecting a lens, a doctor focuses on the following parameters:
- Radius of curvature (curvature of the inner surface of the lens)
- Diameter (distance between the edges of the lens, measured through the center),
- optical power (diopter of the lens, expressed in negative or positive values).
If you want to buy colored contacts, knowing the type that will be suitable for your eye is important. The discussion above will help you select the right lens.
