Glasses, Contact Lenses

Glasses and contact lenses are the most common means of vision correction. They are used to correct vision defects or to protect the eyes. Glasses consist of glasses and frames. The frame ensures the correct position of the glasses relative to the eyes and, using temples or other devices, secures them in the desired position. There are corrective glasses, which correct an optical deficiency of the eye, and safety glasses, designed to protect the eyes from damage or from excessively bright light.

Corrective glasses are used to correct farsightedness, myopia, astigmatism and other vision defects. In a homogeneous transparent medium, a beam of light propagates in a straight line. When moving from one medium to another, it changes its direction - it is refracted. The action of optical glasses, or lenses, is based on this feature of the propagation of light in inhomogeneous media. Parallel rays of light, having passed through a biconvex lens, then travel in a converging direction and are collected behind the lens at one point - the focus. Such glass is called collective, positive, and is designated with a plus sign (+). When passing through a biconcave lens, parallel rays of light travel further in a diverging direction and form an apparent focus in front of the lens. Biconcave glass is called diffusing, negative, and is designated with a minus sign (—). In addition to the mentioned spherical glasses, there are cylindrical lenses with collecting and scattering properties.

Currently, more optically advanced meniscus-shaped glasses, or so-called punctual lenses, are produced, and instead of cylindrical glasses, barrel-shaped toric lenses are produced. The distance from the focal point to the center of the optical glass is called the focal length. The shorter the focal length of the glass, the greater its refractive power. The power of optical glasses is measured in diopters (Dopters). Glass with a focal length of 1 m has 1 diopter. To determine the optical power of any glass, you need to divide 1 m by the focal length of this glass. So, with a focal length of 2 m, the optical power of the glass will be equal to 0.5 diopters (1: 2 m), with a focal length of 0.5 m - 2 diopters (1: 0.5 m).

Contact lenses are a more modern way of vision correction. They are thin discs that are placed on the surface of the eye and perform the same function as glasses. However, contact lenses have a number of advantages over glasses. They provide a wider view without obscuring peripheral vision or interfering with sports or other physical activities. In addition, contact lenses are better at correcting astigmatism and providing a more natural feeling of vision.

Despite their benefits, contact lenses require more care and may be less comfortable for some people. Additionally, they can lead to various eye health problems such as infections, allergic reactions, and even corneal damage. Therefore, before you start using contact lenses, you should consult with an experienced ophthalmologist and receive instructions on how to properly care for your lenses.