Contact lenses: types, how to choose and what you need to know

The advantage of contact lenses is not only that they are invisible. Lenses give brighter and clearer vision than glasses. They are fixed in the pupil area, so you can see well through them in any direction. Since lenses are worn on the most delicate area, the eyes, you need to choose the right model carefully.

Types of Contact Lenses

First of all, contact lenses for the eyes differ in purpose according to the diagnosis:

• For myopia, spherical lenses are prescribed.
• With farsightedness, multifocal lenses with focus for distance and reading or toric lenses are suitable.
• With astigmatism, special astigmatic lenses are prescribed.

Contact lenses differ in hardness. Soft lenses correct vision within a range of -20 to +20 diopters. Rigid lenses increase visual acuity more.

Types of contact lenses by type of material:

• Silicone lenses are 98-99% oxygen permeable, so they are suitable for long-term use. They hold their shape well and are easy to put on. The lenses are dense, so they can feel when you use them. Silicone can cause allergic reactions in some people.
• Hydrogel lenses consist of gel and water. These optics are thin, flexible and elastic. They let in oxygen and retain moisture, but they are not designed for long-term wear. Hydrogel does not allow enough oxygen to pass to the cornea, and over time, irritation and dryness occur. Because hydrogel lenses have poor retention properties, you will need to practice putting them on at first.
• Silicone hydrogel lenses combine the oxygen permeating properties of silicone with the hypoallergenic properties of hydrogel. They are softer than silicone lenses, but denser than hydrogel lenses. Such lenses are worn for about 10 hours a day.

Regardless of the material, all types of lenses, except disposable lenses, have a common feature: they should be disinfected daily in a special solution. This is necessary to avoid bacterial eye inflammation and discomfort. Lenses and their container should not be washed with water. It contains micro particles that can damage the surface of the lenses or contaminate them.

What to look for when choosing contact lenses

When choosing contact lenses for the eyes, consider such factors:

• Contact lenses differ in terms of the period of fitness for use. There are one-day models, and reusable lenses that are replaced once a week, once every two weeks or once a month.
• Depending on the material and stiffness, lenses are designed for different lengths of wear. Some can be used for a day, others from 2 to 7 days without taking off.
• Take into account the moisture content indicator: above 70% is suitable for sensitive eyes, the optimum is 35-50%. Lenses with a high moisture content take over most of the functions of the lacrimal glands, which can lead to a decrease in their natural function.
• The optical power is measured in dioptres (D). Your ophthalmologist determines the D value for glasses and lenses separately, since the D value of these visual aids differs. Computer-assisted diagnosis allows precise determination of the dioptres for lenses.
• BC is the base curvature. It affects the comfort of wearing the lenses.
• Oxygen permeability is indicated in Dk/t. Lenses with a value of less than 80 Dk/t are not recommended to wear longer than 8 hours.
• The sun symbol on the package means that the lenses protect the eyes from ultraviolet radiation.

It is important to remember that although contact lenses are freely available, they are purchased only by appointment of an ophthalmologist. Otherwise, you can make a mistake with dioptres, with the size and rigidity of lenses, and they will be uncomfortable in them. Properly fitting lenses correct vision and rarely cause discomfort.