As a rule every submarine has at least two periscopes, one unifocal with a small upper tube and the other bifocal and sky-searching with a larger upper tube.
The only problem with bifocal lenses was that objects neither far or near were still difficult to focus on, and bifocal eyeglasses also had an unsightly line halfway down the lens that was easy for people to see.
Since multifocal lenses are designed for those with presbyopia, a condition common with aging that causes the inability to focus on objects close by, they are a popular alternative to bifocal glasses.
The computer glasses found at this site also have the bifocal setup with the reading prescription in the bottom of the lenses and the intermediate prescription derived from the stronger one located at the top.
bifocal lenses are a suitable choice for your needs.
Cibavision provides daily disposable contacts, weekly disposable contacts, monthly disposable contacts, contacts designed for astigmatism, cosmetic contacts, bifocal contact lenses, and specialty lenses.
There's no line that immediately jumps from distance vision to near vision, and if you aren't used to traditional bifocal styles, you may find it easier to adapt to the no line bifocal reading glasses than you would to the ones with lines.
Since bifocal lenses often cost a bit more than single vision ones, bifocals that stick onto regular lenses are a good alternative for those who can't afford to spring for the pricier pair of lenses.
bifocal glasses can contribute to balance problems for some people.
You can get bifocal eyeglasses for as low as $25.00 for the whole package.
bifocal spectacles you end up like a nodding donkey trying to focus on different parts of a screen!
Some frame styles are not suitable for bifocal lenses and, on the website, these do not offer the bifocal option.
The effect of newer, bifocal, intraocular lens implants is uncertain.
His most direct contribution to medicine was the invention for his own use of bifocal eyeglasses.
Acuvue Bifocal contacts might be the ideal solution for those who suffer from presbyopia.
Presbyopia can be treated in myriad, if not traditional, ways, including reading, bifocal or multifocal eyeglasses.
However, now there are Acuvue Bifocal contacts that are specifically designed for presbyopia.
However, that isn't to say that bifocal wearers cannot find a great match within this line as there are some deep frames in the lineup.
If you are looking for an alternative to reading glasses, bifocal contact lenses may be an option for you to consider.
If a lined bifocal is prescribed, then the line is always placed higher for the child than for the adult.
This is done to encourage use of the power of the bifocal.
Benjamin Franklin is credited with creating bifocal lenses.
Dr. John Borsch, Jr. made improvements upon Benjamin Franklin/Samuel Pierce's bifocal lenses by making them thinner and more attractive.
Improving upon the bifocal and trifocal concepts, a new lens called Varilux was born.
Eventually those lenses became available in a progressive (line-free bifocal) style.
No line bifocal reading glasses are sometimes known as progressive bifocals.
What could be better than inexpensive bifocal glasses without lines?
You can get the bifocal eyeglasses for as low as $79.
While that is expensive compared to most drugstore readers, compared to most eyeglass frames with no line bifocal lenses, it's quite a reasonable price.
If you're finally at the point where you need reading glasses to make it through the day, no line bifocal reading glasses might fit the bill.
This can be corrected with a higher diopter measurement for glasses or the adoption of bifocal or trifocal lenses as needed.
They are clear at the top and have a bifocal power of +1.50 at the bottom.
Because they aren't custom made with your own prescription in the top and a bifocal power in the bottom, you can get them at a reasonable price, often between $25 and $65.
The bifocal section (there is a line) is positioned on the back of the lens, so it's less obvious that you're wearing a pair of bifocal lenses at all.
Choose a frame that is deep enough to hold a bifocal.
Polarized prescription lenses are available in single vision and bifocal versions.
The prescriptions are slightly different between the left and right contacts; they don't work like bifocal glasses where your distance and reading prescriptions are in each lens.
Safety Glasses has prescription and even bifocal safety glasses.
To measure the height of the bifocal, put your frames on and look straight into the mirror.
Roughly two millimeters below your pupil is where the top edge of the bifocal should go.
New bifocals wearers will, of course, have an adjustment period just as they would with any type of bifocal.
There are a few reasons you may want to skip the stick on type of bifocal and opt instead for a set of reading glasses if the cost of bifocal lenses is what's putting you off.
If reading glasses are not of interest to you, consider bifocal contact lenses.
Each style uses various powers much like an eyeglass bifocal lens does.
The advantage of bifocal contacts is that you won't need to take your reading glasses off and on.
Bifocal contacts are less noticeable than reading glasses since you will not need to look over or under the frames or take them off and on like you would with glasses.
You will be able to instantly see the object clearly no matter what distance it is at when wearing bifocal contacts.
Most bifocal lenses take a period of adjustment.
Acuvue Bifocal are made with a unique design called Pupil Intelligent Design.
Acuvue Bifocal will allow 88 percent of oxygen to your eye.
Another bifocal lenses from Acuvue is the Oasis for Presbyopia.
They are the only bifocal lens that comes in silicone hydrogel, which allows oxygen to the eye.
If you don't want to be bothered with a pair of reading glasses, consider bifocal contacts.
Ask your eye care professional if wearing bifocal contacts is right for you.
The bifocal portion of the lens will not interfere with your driving if positioned properly.
The difference comes in when it comes to the placement of the bifocal itself.
That way, when you look down in regular reading position, your eyes automatically find themselves looking through the special bifocal lenses.
In a way, though, it is up to you to decide where to put the bifocal lenses.
Also, the measurement is different from the straight top bifocal.
Also, you'll want to ask for a gradient tint so that the bifocal lenses will be darker at the top and get lighter toward the bottom.
However, they are available in progressive or traditional straight top bifocal lenses.
The traditional bifocal design has a prescription for seeing at a distance in the top part of the lens.
In most cases, the bifocal portion is called a "straight top" because the line, as the name suggests, is horizontal across the bottom of the lens (a little lower than halfway down the lenses).
Bifocal lenses like these are not available at the drugstore and will have to be custom-made for you.
Bifocal Needs: Typically bifocals mean that one segment of the lens aids with near vision difficulties, while another segment takes care of things at a distance.
You might want to invest in frames that are a little more durable if you can afford it, and you can get bifocal lenses if they fit your needs better.
Another possibility is that the depth of a progressive bifocal won't all be left on the lens, stopping short before offering you the reading power you need at the bottom of the lenses.
He invented bifocal glasses, which are comprised of lenses to correct both conditions so one only needs to shift the angle of the eye to see clearly.
The bottom portion of each lens, however, has a magnifying section, much like a bifocal, so that when you look down as if to read something, you're looking through that part.
To determine whether you need or want bifocal readers or reading glasses, you'll need to consider a few things.
If you do, it may make more sense to choose a pair of bifocal glasses from your local optical shop than to choose a pair of bifocal readers or reading glasses at all.
A pair of prescription bifocal eyeglasses will cover both, removing the need to switch out your eyeglasses based on whether you're reading, watching television, or driving around town.
While you could technically go to any optical shop and have your bifocal readers custom made, there's no need to do that.
You can save up to hundreds of dollars by purchasing pre-made bifocal readers in a drugstore or online.
Though you may be able to pick a pair up in your local drugstore or optical shop, bifocal readers are less ubiquitous than your average pair of readers.
Once you know the strength you need in regular readers, you'll know which strength to buy in bifocal readers.
Peeper Specs: Just type bifocal readers into the search box and you'll get a list of what they have to offer.
Boomers in the Know: This site has a surprising selection of bifocal readers.
Choose bifocal readers if you don't need a prescription to see distant objects and you feel that you're always wearing reading glasses.
For those needing special lenses such as bifocal or multifocal lenses, Eyeglass World has those as well.
In fact, you may even have a pair custom made for your specific needs, including bifocal lenses.
If there is a number listed under the "Add" column, that is your bifocal strength.
Over the counter invisible bifocal shades come with typical reading glasses prescriptions like +1.00, +1.50, +2.00, +2.50, and +3.00.
Many people need bifocal glasses to help them see clearly when reading.
Makaha Reader is another bifocal style that can be worn for just about any outdoor activity.
It has a hidden bifocal that is positioned so you can see at all distances.
Maui Jim uses several types of sunglass lens for their bifocal glasses.
Many shy away from bifocals since traditional bifocal lenses have a distinguishable line that separates the two prescriptions and can be noticeable on lenses.
Eventually, the optical field developed what became known as bifocal lenses.
Some people call these lenses multi-focal, progressive bifocal, or simply progressive reading glasses.
Best of all, progressive reading glasses don't have any visible lines on the lens like bifocal glasses did.
Bifocal heights also have to be measured with the chosen frame in place and adjusted on the person.
If bifocals are prescribed, then either progressive or no-lines, or a lined bifocal may be given.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.