In the beginning, let's know what glasses and medical lenses are?
And the word (glasses) in the language means eyes, It is a way to fix vision problems in the eye, such as farsightedness, myopia (myopia) or astigmatism, and it is also used to treat some cases of strabismus or after cataract surgeries.
They are optical means to refract light as it passes through them, and they are made of transparent azeotropic materials such as glass, and they have spherical surfaces where the surfaces of the lens are either equal or different in curvature, according to the purpose for which the lens is used. The line connecting the two centers of curvature in one lens is known as the "axis the lens".
The lenses are concave or convex on one or both of their surfaces, where refraction occurs in light rays falling on one of their sides. The convex lens is used to collect the light rays into the focus. While the concave lens is used to disperse the rays, the concave lens also has an imaginary focus.
The preferred lenses for eyeglasses are the transparent lens, but it may be recommended to use colored lenses in cases of allergic eye diseases or when the eyes are sensitive to light.
Despite the emergence of modern technologies in the field of low vision treatment, such as LASIK, eyeglasses are commonly used to this day and are the solution for most of those who suffer from low vision, whether after or nearsightedness, or even in the treatment of astigmatism.
Medical lenses are made of two materials:
The use of glass in the manufacture of lenses has become less common due to weight and because of the risk of breakage because glass is a fragile material.
Plastic lenses are the most widely used in the world of medical lenses because they are shock-resistant, low in weight and easy to produce.
Types of eyeglass lenses :
The type of lenses is selected based on the eye specialist’s diagnosis and is divided as follows:
1- Spherical lenses:
It is a lens consisting of two surfaces, so that each of them is part of the surface of the sphere, and it is either a convex lens (collected) or a concave lens (split).
A- Convex lens (collected):
These lenses are thicker in the middle and thinner at the edges
b- Concave lens (split):
As for this lens, it is opposite to the convex lens, which means that it is thinner in the middle and thicker at its edges.
2- Aspherical lenses:
They are lenses in which the two surfaces or one of them is spherical or cylindrical. And this type of lens is more clear and has less aberration than spherical lenses. And this type of lens is more expensive than spherical lenses.
These lenses are used to treat cases of astigmatism, and are curved in one direction more than the other
But there are some cases that suffer from long-sightedness and short-sightedness at the same time, and it is known as: presbyopia, which is often suffered by the elderly. In this case, special lenses are selected and are divided as follows:
1- Bifocal lenses, also known as (Bifocal):
They are lenses that provide two prescriptions in one lens. The first prescription is for close reading, and the other prescription is for normal and long distance vision.
2- Trifocal lenses, also known as (trifocal):
They are lenses that provide three prescriptions in one lens, the first prescription for far vision, the second for near vision, and the third for medium vision.
3- Multifocal lenses, also known as (progressive lenses):
This is one of the best types of lenses that combine reading glasses and vision at the same time.
As these lenses are an advanced update of bifocal and trifocal lenses and work to gradually change the energy from the top of the lens to the bottom so that the person can see clearly and look comfortable in the eye.
Finally, we will give you some tips to maintain your eyeglasses:
1- When you do not use your medical glasses, it is preferable to put them in their cover to avoid breaking them and keep them in a safe and sound place
2- Avoid using tissues or towels to clean the lenses.
3- It is important to wash it with warm water and then wipe it with a soft cloth so that dust particles do not scratch the lens
4- It is important not to wear glasses on the head, as the upper area is larger than the eye area and will therefore be unsuitable for the size of the eyes.
5- In order to preserve it well, it is preferable not to put it in the pocket or on the neck, but rather put it in its own cover so as not to cause it to be scratched.
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