Posts Tagged ‘bifocal lenses’

What Do You Know About Some Common Multi-focal Lenses?

April 12th, 2010

This history of glasses lenses can be dated back to more than eight centuries ago. However, those lenses we often use till now are almost single vision and the lenses with multiple focuses did not come into being until the emergence of bifocals. It was the 18th century that witnessed the appearance of the first bifocal lenses. And who is the first bifocal lens inventor? Till now, the universally recognized inventor is Benjamin Franklin, one of the most reputable state men in then US. He found it was impossible for him to read or see other objects with ordinary single vision lenses (he may have both Presbyopia and near vision problems at the same time). He then tried many methods to solve those problems by overlapping two different lenses. And the results prove to be practical.

Theoretically, multi-focal lenses, also called varifocal lenses, have more than one vision areas comparing to ordinary lenses. Bifocals listed above are just such typical example, with two focuses. In fact, there are still some other multi-focal lenses that can be found in optical stores, in addition to bifocals.

Trifocals, also called trifocal lenses, are much advanced products than bifocals. They have three vision areas in the same lenses, namely, near, intermediate and far vision areas. They can provide wearers with much greater comfort while they have to look at objects of different distance.

However, there is a disadvantage in both bifocals and trifocals- there is an evident division line among each vision areas. Because eyes have to endure the pain of transmitting from one area to another, some wearers can not withstand such radical vision changes. Therefore, much advanced lenses are needed.

Therefore, the coming of progressive lenses has satisfied people’s demands. Those lenses are really multi-focal, for the transition among any vision area is very natural and no aforesaid lines can be detected on them. So, wearers of such lenses will never suffer from pain caused by radical vision changes. And the result is more and more people love to wear those lenses. Moreover, progressive lenses often come together with bifocals and trifocals.

Multi-focal lenses are always in the process of evolution, through which more and more achievements are scored.

Astigmatism and Bifocal lenses

March 30th, 2010

Bifocal lenses are proved to be very useful in curing some particular eye problems. Of which, astigmatism can be effectively by them.

Astigmatism, one of the most common eye problems among glasses wearers, has caused a lot of troubles to sufferers. Sufferers of this disease always have blurred vision, for the images of any object can not be directly and accurately projected on the retina. Just because of this, they will have to endure double vision that may cause dizziness if such symptom can not be treated. Generally, based on the causes, astigmatism can be fallen into two sorts, namely, regular and irregular astigmatism. However, any one of the two types is caused by the damage or deformation in cornea or lens.

As so many troubles will be caused by this problem, many sufferers want to get rid of it completely. People have tried every possible effort to tackle it since the problem occurs. And now, there is a very effective ways for it- Wearing bifocal lens for astigmatism is a well-known solution. Here is some specific information about it.

Bifocal lenses are some of the best alternatives to cure astigmatism. Maybe the bifocal lenses history is firmly related to astigmatism. The data has it that the history of those lenses is much shorter that ordinary lenses, only about two and a half centuries. The first bifocal lens inventor is legally said to be Benjamin Franklin. He might be one of the sufferers of astigmatism when he was old. Because he was such a wise and creative man that he had found the solution ultimately. Or he might be a sufferer of other eye problems, as presbyopia, and he made such lenses that were also very useful in treating astigmatism. Anyway, bifocal lenses are very nice alternative to deal with astigmatism.

As for bifocal lens types, there are lined bifocals and no-lined bifocals. This first type is the oldest and commonest member in the family. There is an evident division line in the middle of the lenses. The second type is the latest member in the family. As no such division can be found in those lenses, they are also called progressive bifocals at the same time. And the two types are very good alternatives for people with astigmatism.

All in all, astigmatism can be successfully cured by wearing bifocal lens for astigmatism, and every sufferer of this problem may have a try.

What should People Know Before Buying Bifocal Lenses?

March 26th, 2010

Bifocal lenses are some of the most beloved products for people with presbyopia and other eye problems, like astigmatism, myopia at the same time. However, here is some very information people should know if they want to buy bifocal lenses.

Generally, according to the comfort they can bring to wearers, bifocal lenses can be fallen into two sorts, namely conventional bifocal lenses and bifocal progressive lenses. There is some evident difference between the two- a division line. Conventional bifocal lenses have an evident division line in the middle of the lens, whereas no line can be found in bifocal progressive lenses. Therefore, the former type is called lined bifocal and the later form is called no-line bifocal. However, each of the two sorts has their own merits according to people’s different demands.

Some people may wonder how do bifocal lenses cost. The answer depends. Just because more efforts should be spent in making them, bifocal lenses are much expensive than ordinary lenses. That’s to say, people have to pay more money if they buy bifocal lenses than ordinary ones in the same place. However, there are some exceptions. If those lenses can be purchased from online vendor, they will be much cheaper than ordinary lenses from real optical stores. In addition, conventional bifocal lenses are cheaper than bifocal progressive lenses. This is because progressive lenses are some of the latest products in the industry. And their prescription and manufacturing process are much complicated than conventional ones. But there are also some exceptions among the two types. There are some high-end conventional bifocal lenses that cost very much and there are also cheap bifocal progressive lenses that can be afforded by almost all wearers. Anyway, people should choose the ones that fit their condition and situation most.

However, there are still some bifocal lenses problems. That’s to say, there may be some problems on the lenses due to different causes. And one of the great causes is wrong Prescription. Bifocal lenses must be prescribed in very accurate and meticulous way. Therefore, once any problem occurs on the prescription, there will be some problems in the lenses.

All in all, there is much other information about those lenses and people may visit some glasses websites if they want to know more about it.

The Evolution of Bifocals

March 22nd, 2010

What will people do if they have some very serious eye problems, like astigmatism, presbyopia, myopia, etc, especially when they are over forty? They may choose to wear bifocal lenses without any hesitation. It seems that those lenses are very common and sufferers of the above mentioned problems have got used to them. However, unlike common lenses, bifocals have really very short history, but they have evolved radically since their first emergence.

According to the data from bifocal lenses Wiki, the bifocal lenses history is no more than two and a half centuries. It is said that bifocals do not come into being till the 18th century. And there are still some controversies about who is the bifocal lenses inventor. However, the universally recognized inventor is Benjamin Franklin, a well-known US state man in the 18th century.

It matters little who have invented the first bifocals, but it matters much what the first bifocals are looked like. According to some documents, the first bifocals are roughly manufactured and very heavy to wear and inconvenient to use. The reason is each lenses are directly overlapped by two full lenses. Therefore, there are almost four full lenses on each pair of them. And such condition does not change until the 20th century.

The 20th century has witnessed the rapid developments and changes in glasses industry. And bifocals have also gained great rapidity then. Some designers have noticed that conventional bifocals are roughly made and have caused lots of troubles to wearers. Based on all possible scientific data in the industry, designers have combined each lens by two cut lenses. This innovation has greatly enhanced the comfort of wearing. Now that those lenses are combined by two different lenses, there is a division line between them. And there comes bifocal progressive as a result. Here is a contrast- bifocal lenses Vs Progressive.

The first type is called lined lenses and has very evident division line in their middle part, whereas no such line can be found in the latter form. Wearers will endure radical vision change with bifocal lenses, but never with progressive. And many people begin love to wear progressive thereafter.

Bifocals are always in the process of evolution and people will benefit from it. For example, some bifocal lenses for spectacles are available if people want to replace them.

Progressive lenses with a range of powers

February 1st, 2010

Progressive lenses are corrective lenses used for presbyopia and other eye problems. They are special because of their gradient of increasing lens power. Progressive lenses have several names, such as progressive addition lenses (PAL), progressive power lenses, graduated lenses, no-line bifocals, and varifocal lenses. All of these names can reflect some of the features of progressive lens.

People look down for close reading so that the gradient of progressive lenses starts at the top of the lens, at a minimum power and reaches a maximum addition power at the bottom of the lens. This structure of progressive lenses provides the most comfortable and convenient reading effect. The power gradient length of progressive lens is usually between 15 and 20mm. The power addition gap of progressive lens is between 1.0 to 2.5 which depends on the level of presbyopia of the patient.

Just as the name no-line bifocals suggests, progressive lenses have relationship with bifocal lenses, which have visible lines on the lenses. Progressive lens just eliminates the lines on bifocals and trifocals, so that others will not find that you need reading glasses. This is one advantage of progressive lenses.

Bifocal lenses and trifocal lenses provide two or three lens power on the lens, while progressive lenses provide a seamless progression of many lens power. Progressive lens performs well in more situations, including intermediate zone computer reading. In contrast to several lens power, progressive lenses just provide a more natural correction.

Progressive lens is not perfect. As the lenses combine a range of powers in a single surface, geometric distortions may be caused to visual field, which in turn bring visual discomfort.

Presbyopic people benefit from new contact lens—-bifocal lens

December 3rd, 2009

In the family of corrective contacts, bifocal lens is totally different. This is because bifocal lens has some characteristics that others do not have. Since the day when bifocal eyeglasses were invented by Benjamin Franklin, they have helped a lot of people. And now they have become much perfect though the mechanism is still the same.

People who have been diagnosed as presbyopia are in need of bifocal lens. For the uniqueness of presbyopia, there are still many problems in solving them. The patients either can see the objects near and far simultaneously, or can they move their eyes freely. As for these symptoms, people have designed bifocal lenses to tackle with them.

By and large, people can find two kinds of these lenses at the market, namely, alternating bifocal lenses and simultaneous bifocal lenses. When people look upward or downward, alternating bifocal lenses can help a lot, because pupils can notice the two power distance between distance and near powers. As their names indicate, simultaneous bifocal lenses can make sure that the two powers can be looked at the same time.

Though bifocal lenses are mainly for people suffering presbyopia, not all of the presbyopia suffers can wear these contact lenses. Each bifocal lens should fit the conditions of individual patients. Some repulsive effects may happen to people who can not wear bifocal lens. Some criteria must be met if presbyopic patients need to be prescribed bifocal lenses. They should have very good tear system, healthy cornea, and normal blink rates. If they fail to meet these requirements, bifocal lenses are not suitable for them.

Additionally, some items need to be noticed when storing and cleaning bifocal lens. In order not to be infected, hands should be clearly washed before handling these lenses. Moreover, bifocal lens should be cleaned regularly using proper solutions.