Posts Tagged ‘Trifocals’

Merits and Demerits of Bifocals and trifocals

April 7th, 2010

Bifocals and trifocals are two of the most important varifocal lenses in people’s daily lives. Each of them has their own advantages and disadvantages. Here is some wanted information about the two lenses for many people, especially those new wearers.

Bifocals have two different vision areas, each of which is responsible for near vision and far vision respectively. But many people may hear from others that bifocal lenses problems are really very troublesome. This is partly true. All those problems are mainly caused by their unique structures. Those lenses are combined by two different cut lenses. That’s to say, each of them is responsible for vision at different distance. And many wearers may suffer from very serious dizziness and headaches occasionally when they change their vision radically. The reason is the optic nerves in wearers’ mind can not react in time with the vision change, and the brain will suffer greatly as a result. Another very common symptom is almost all people will spend some time to adapt them, though the time varies a lot.

In order to solve those problems caused by bifocals, lots of designers and professionals have spared no efforts to improve them. Later, the birth of varifocal bifocal lenses has satisfied wearers’ demands to some extent. Those lenses can ensure wearers enjoy great vision clarity and comfort without any aforesaid complications.

Trifocals are more advanced lenses than bifocals in some senses. There are three different vision areas in those lenses, namely, areas for far vision, intermediate vision and nearby vision. This design can help wearers more easily get used to them and reduce the chances of radical vision transition. Therefore, the cost of trifocal lenses is much greater than some bifocals and other conventional lenses. But there are some exceptions if wearers buy them from different retailers. For example, products from online vendors are much cheaper than optical stores. Still, people can also ask for help from certain Insurance Companies who provide such services sometimes.

In a word, those bifocal trifocal lenses can effectively help solve some particular eye problems, though people may withstand some discomfort while wearing. There is a trend that more and more innovations are made on them and more comfort can be found on them as well.

Differences between Trifocals and Bifocals

November 21st, 2009

Trifocals are a new group of special reading glasses which have three divisions on the lenses for correcting vision. It is different from traditional bifocals which have only two such divisions. The lower sections of the lens of trifocals are demarcated by a thin line which is a semi circular arc. One area is for near and the other for intermediate vision correction. And the part for intermediate rectification lies above the nearsighted correction area which is near the bottom of the lens. For those who used to wear bifocals may think it is strange to reading with glasses having three lines etched on it. As trifocals are new to most of people, it actually did need time for patient who uses this type of glasses to adjust to them. However, once you used to wear them, you will find it pretty easy to use and it is more convenient than bifocals.

After eye exam by the eye doctor, those people with extreme presbyopia, which means their net optical power with a special unit of diopter is very high, will be recommended to use trifocals. Because, unlike bifocals, trifocals can correct all ranges of vision, from nearby, intermediary to far distance, when bifocals can correct only two of them, either near vision or distance vision. Since trifocals can offer three levels of correction, it can give you a better vision. So, if you are one of the extreme presbyopia, you will get the better and more clarified vision when you use trifocals.

Trifocals are not only for those who have extreme presbyopia, it can also correct intermediate distance which can’t be provided by bifocals. For example, if your have a vision of -4 diopters, usually you will be recommended to use a glasses with a correction of 3 units, which means you vision is -1 diopter when you wear your reading glasses. The intermediate correction for such situation may be end up with a power of -2.5, which may take patients a little time to get used to it.

So with a single pair of trifocals, you can solve all problems that are related to presbyopia.

What Do You Know About Trifocals?

November 10th, 2009

People over 40 mostly find their eyes lose their capacity to adjust and focus on different things. This is a common biological change. As body ages, our eyes age as well, resulting in presbyopia, a term derived from Latin with the meaning of ‘ageing eyes’. This is different from myopia and hyperopia which are caused by deficiency of eyes and can not be cured by corrective glasses, refractive surgery or contact lenses. People with presbyopia usually use trifocals.

Trifocals are glasses where the lenses have 3 regions to correct for distance, intermediate (arm’s length), and near vision. They most used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading addition. Compared with bifocals, trifocals provide more clear vision to the wearer although, in some degree, they sound to be tougher to see through.

Those who have ever worn bifocal glasses may know that at the very first time when they wear them, they often feel hard to get used to bifocals. They frequently feel dizzy. The insertion of the intermediate addition of trifocals which steps between the distant and reading distance make things easier for a person to progress one step to another. The intermediate addition is normally half of the reading addition and half of the long addition. So for someone with a distance prescription of -4 diopters and a reading addition of +3 diopters, the reading portion of their trifocals would have a net power of -1, and the intermediate segment would be -2.5 diopters. Thus, those wearing trifocals obtain clearer vision and experience less strain on the eye than those wearing bifocals.

Therefore, we can see, based on the same principle, trifocals, only differing from bifocals in vision of divisions, are equipped with three additions rather than two. Trifocal is a type of glasses belong to multifocal glasses.

Just like bifocals, trifocals are also equipped with the semi-circular area with each the reading addition and distance addition. Meanwhile the mid-range of trifocals are equipped with a narrow band, for people seeing things that are not very far but further than the reading distance. If you frequently spend your time before a computer, trifocals will provide you with great comfort.

Trifocals offer the wearer the benefits of three corrective prescriptions without the need for three separate pairs of glasses. For those who want the benefit of trifocals without telltale lines, there are progressive lenses, which may also be called progressive addition lenses or PALs, progressive power lenses, graduated lenses and varifocal lenses. These terms may be used to describe ‘no-line’ bifocals as well.