عینک طبی تک دید

The best medical lenses for glasses

The best eyeglass lenses

The best eyeglass lenses


Glasses lenses: Overview
The type of lenses in your glasses play a big role in your vision, comfort and safety when wearing eyeglasses. And buying the best lenses for your glasses is not an easy task. There are many different types of eyeglsass lens materials and designs, and each has its own features, benefits, and cost.

:The lenses you choose for your glasses influence four factors

Vision –

Comfort –

Appearance-

Safety –

The following information will help you buy eyeglasses lenses wisely. It applies to prescription eyeglass lenses that correct nearsightedness, farsightedness and astigmatism. It will also help you choose the best progressive lenses or other multifocal lenses if you have presbyopia.

 

Eyeglass lens materials

Glass lenses

In the early days of vision correction, all eyeglass lenses were made of glass. Glass lenses offer exceptional optics. But hey are heavy and can break easily, potentially causing a serious eye injury or even loss of an eye. For these reasons, glass lenses are no longer widely used for eyeglasses.

Plastic lenses

The first plastic eyeglass lenses were developed in the 1940s. These lightweight alternatives to glass lenses were call CR-39 plastic lenses. Plastic eyeglass lenses are about half the weight of glass lenses. They are relatively inexpensive and have excellent optical qualities. They also are more impact-resistant than glass lenses.

Polycarbonate lenses

The first lightweight polycarbonate lenses for safety glasses were introduced in the 1970s. Since then, polycarbonate lenses have surged in popularity. They are lighter than regular plastic eyeglass lenses and significantly more impact resistant. Polycarbonate is a great lens material for children’s eyeglasses, safety glasses and sports eyewear.

Trivex lenses

Trivex, a new lightweight and impact-resistant eyeglass lens material, was introduced in 2001. Trivex lenses are a good alternative to polycarbonate lenses. They are lightweight and have slightly different optical and impact resistance qualities. [Read more about Trivex vs. polycarbonate lenses.]

High-index plastic lenses

In the past 20 years, several different types high-index plastic lenses have been introduced. These lenses are significantly thinner and lighter than regular plastic lenses. They have a higher index of refraction and are available in an aspheric lens design (see below for more about these).

Comparing lens materials

Here are popular eyeglass lens materials, arranged in order of refractive index and lens thickness (pretty good indicators of cost). Except for the crown glass, these are all plastic materials.

 

Eyeglass lens features

Here are details about important features of lenses for your glasses:

Index of refraction

The index of refraction (or refractive index) of an eyeglass lens material is an indicator of how efficiently the material refracts (bends) light. This efficiency is related to how fast light travels through the material.

Specifically, the refractive index of a lens material is the ratio of the speed of light in a vacuum, divided by the speed of light in the lens material. For example, the index of refraction of CR-39 plastic is 1.498. This means light travels roughly 50% slower through CR-39 plastic than it does through a vacuum.

The higher the refractive index of a material, the slower light moves through it, which results in greater bending (or focusing) of the light rays. So, the higher the refractive index of a lens material, the less lens material is required to bend light to the same degree as a lens with a lower refractive index.

In other words, for a given eyeglass lens power, a lens made of a material with a high refractive index will be thinner than a lens made of a material with a lower refractive index.

The refractive index of the most popular eyeglass lens materials used today ranges from 1.498 (CR-39 plastic) to 1.74 (a type of high-index plastic). For the same prescription power and lens design, a lens made of CR-39 plastic will be the thickest and a 1.74 high-index plastic lens will be the thinnest.

Abbe value

The Abbe value of a lens material determines how much chromatic aberration the lens produces. This is an optical error that causes colored halos around lights.

Lens materials with a low Abbe value can cause noticeable and bothersome chromatic aberration.

Chromatic aberration is most noticeable when looking through the periphery of eyeglass lenses. It is least noticeable when looking directly through the central optical zone of the lenses.

Abbe values of eyeglass lens materials range from a high of 59 (regular glass) to a low of 30 (polycarbonate). The lower the Abbe number, the more likely the lens material is to cause chromatic aberration.

Abbe number is named after the German physicist Ernst Abbe (1840-1905), who defined this useful measure of optical quality.

SEE ALSO: How To Clean Glasses — Without Scratching Your Lenses!

Aspheric design

Glasses lenses with an aspheric design have a slimmer, more attractive profile than regular lenses.

In aspheric lenses, the curvature of the lens changes gradually from its center to its edge. This enables the use flatter curves when fabricating eyeglass lenses.

Because aspheric lenses are flatter than regular lenses, they cause less unwanted magnification. This makes the wearer’s eyes look more natural in size and appearance. In some cases, aspheric lens designs also improve the wearer’s peripheral vision.

Most high-index plastic lenses are aspheric to optimize both appearance and optical performance. With polycarbonate and CR-39 lenses, an aspheric design is optional and available for an added cost.

Center and edge thickness

In the United States, the U.S. Food and Drug Administration (FDA) has issued guidelines for impact resistance of eyeglass lenses. For this reason, there’s a limit to how thin an optical laboratory can grind your lenses.

In lenses for the correction of myopia, the thinnest part of the lens is the optical center, located at or near the middle of the lens. The thinnest part of eyeglass lenses that correct farsightedness is at the edge of the lenses.

Because of their superior impact resistance, polycarbonate and Trivex lenses can have a center thickness of just 1.0 mm and still pass the FDA impact-resistance standard. Myopia-correcting lenses made of other materials usually have to be thicker in the center to pass the standard.

The size and shape of your eyeglass frames also will affect the thickness of your lenses. This is especially noticeable if you have a strong eyeglass prescription.

Choosing a smaller, well-centered frame can significantly reduce the thickness and weight of your eyeglasses lenses, regardless of the lens material you choose.

عدسی طبی

Anti-reflex layer

Eyeglass lens treatments

For the most comfortable, durable and best-looking glasses, the following lens treatments should be considered essential:

Medical lenses smoked

The best medical lenses for glasses

 

 

Medical lenses are the thing that can fix your visual impairment.

Usually, people suffer from eye weakness due to several reasons, the most common of which are heredity problems and old age

  1. And they should use prescription glasses.

Be careful in buying prescription glasses

All of us when we buy the equipment we need… especially from the equipment that is supposed to last a long time.

to use, we try to get information about that device before buying

We may even spend several days for the best choice.

Today, despite having the Internet, we can easily search with a little

Information such as:

Different models… manufacturing countries and sales centers and most importantly the price of the productر

We intend to get Today, despite having the Internet, we can easily search with a little

Information such as:

Different models… manufacturing countries and sales centers and most importantly the price of the product

We intend to get

Unfortunately, what I have to say is that:

Many of those who want to buy prescription glasses for themselves or their loved ones

Simply buying a chip or puff will do this

Without researching in this field or at least searching a little to find the right price

In particular, it should be noted that:

It is far more important than the frame of the glasses

And you will be most satisfied with your prescription glasses because of the type of lens.

One of the main reasons for buying without research is that:

In almost all grading centers and ophthalmology offices, there is a section for selling glasses

After you come out of the ophthalmologist’s or optometrist’s room… immediately with the glasses seller

You meet.. this is where you either become polite or because of the suggestion of the optometrist or the doctor himself..

You get the glasses from there.

Without having a chance for a simple search on the Internet. Without having a chance for a simple search on the Internet. 

Most of those who express dissatisfaction after buying, especially because of the price. There are two reasons.

Second, they say that when we go to a reputable and famous clinic, we assume this

which is reliable in every way.

This is despite the fact that all these eyeglass shops inside clinics or offices are all these eyeglass shops inside clinics or offices

They work on a contract basis (paying rent or a percentage of sales) and due to the high costs they have, they do not perform according to the obligations and services of that center.

The good or bad performance of the glasses shop in any reputable clinic is not under the supervision of the clinic management.———————

Although the science of optics is quite specialized and has complications, many people think that they should not get into it and leave the choice to others.

But remember that you are not going to learn all the ins and outs of this profession

What is intended: knowing the minimum information about your vision problem and the glasses that you are going to have for years. Is.

Knowing what your eye score is, what was the brand of your previous lens, and which model is the best type of lens or eyeglass lens according to your needs, is not a difficult or complicated task.

Please pay attention to this point

The glasses frame you choose is important for both comfort and beauty.

But the eyeglass lens she chooses affects four factors:

Appearance … comfort … quality of vision and safety

So please take enough time to buy prescription glasses.

 

Information about the types of eyeglass lenses or medical lenses

Medical glasses can be purchased in different types according to the vision needs of the person

Which depends on many factors to choose the best type. Which depends on many factors to choose the best type.

Three fields of view

Far vision… Middle vision… Near vision

Often vision problems can occur for far vision or near vision or reading.

Lenses that solve only one of these problems are called takidid lenses.

 ( Single Vision )

Those who have weak eyes and astigmatism… both for far vision and for reading

They use contact lenses.

In fact, a person who does not see well near and far vision should have two for himself

Get glasses. One for traveling and one for studying.

And if the difference between the weak value of far vision and the score of near vision is high

She should also get a separate pair of glasses for working with the computer

which is called the middle vision range.

Now, if due to presbyopia or other reasons, they have weakness in both ranges.

Instead of having two glasses (one for distance and one for reading),

Use a bifocal or multifocal lens.

Without having a chance for a simple search on the Internet.

Most of those who express dissatisfaction after buying, especially because of the price.
There are two reasons.
First of all: they are suffering from depression and cannot say no easily.
Second, they say that when we go to a reputable and famous clinic, we assume this
which is reliable in every way.
This is despite the fact that all these eyeglass shops inside clinics or offices
They work on a contract basis (paying rent or a percentage of sales) and due to their high costs.

According to the obligations and services of that center, they do not act.

The good or bad performance of glasses sales in a certain reputable clinic is not under the supervision of the clinic management.

 

 

 

 

 

The best medical lenses for glasses

ورود به قسمت های سایت

قیمت انواع عدسی های طبی دودید و تک دید

فریم عینک مناسب برای عدسی های دودید و تدریجی

تفاوت بین عدسی بلوکنترل و بلوکات

انواع عدسی های دودید و تدریجی

میزان فشردگی لنز طبی عینک

جنس و متریال عدسی های طبی

خاصیت انواع عدسی طبی 

ضخامت عدسی های طبی

عدسی بلوکات و بلوکنترل

انواع عینک طبی آفتابی

بیماری های چشم

عدسی پلاریزه

لینک خارجی

 

 

نوشته های مشابه

دیدگاهتان را بنویسید