Someone having many vision problems needs to have multifocal glasses and amidst the various multifocal lenses, most people have a yearning for bifocals.
You can see things at any distance with the aid of bifocals and using this needs you to use it every time.
This bifocal helped the people to get rid of the hazard of using a couple of different eyeglasses.
In fact, it also caused problems in different circumstances.
Most people who are lacking of vision use eyeglasses and bifocals are preferred.
This is of paramount significance for problems like presbyopia which normally seen in the 40's.
It is caused due to the steady failure of the usual flexibility of the lens inside eye.
Trifocals fall in the category of multifocal glasses.
Such lenses are followed by three separate stages of prescription like bifocals with just the addition of a level called correction.
This can be applied in case of vision problems of any distance whatsoever.
In trifocals, there are three places for correction of long, middle and short distance.
If someone is suffering from presbyopia seriously, trifocals can be of immense importance as they are advised to use two or more diopters.
In case of intermediate addition, it is usually half the reading addition.
If you are provided with a prescription of -4 diopters and a reading addition of +3, the trifocals' reading part is going to have a power of -1.
In this aspect, in-between section is likely to be -2.
5 diopters.
The region looking like a semi-circle near the base of lens, having two horizontal lines in order to demarcate the 3 prescriptions in trifocals, covers the near and middle length.
Correction's near range gets very close to the base of lens.
This gets chiefly used during reading or during such minute work.
Near the center of lens, you get the in-between range of trifocals that is needed at the time of viewing something situated at middle range.
Although it is the thinnest band of correction, this middle area can be turned into bigger one.
If you have to spend great share of time with computer, this can be of immense use.
Once it crosses the mid-range, one has to depend on the topmost section of the trifocals.
Having a prescription this section also proves to be helpful for problems like nearsightedness or farsightedness (it is different from presbyopia).
Higher level of presbyopia seriously needs trifocals.
The word is derived from the Latin words that stand for "aging eyes," and refers to a decline in visual adjustment.
Normally, people start to feel some problems in viewing the small printed things after they get 40 years of age.
One can fight with this with the aid of refractive surgery or contact lenses and also with glasses having corrective lenses.
Importantly enough, trifocals let you be free from the problem of using three different pairs of glasses.
You can opt for progressive lenses in case you want to avoid the snitch lines.
Progressive add (ition) lenses or PALs, progressive power lenses, graduated lenses, and varifocal lenses are some of its variation in name.
A "No-line" bifocal is another such variation.