Progressive lenses were first introduced in the 1990's as a new lens product that offers multifocal vision "without the line". Lens companies realized that aging customers did not like other people seeing the visible bifocal line for cosmetic purposes. So the progressive "no-line" lens was invented, and marketed well under such names as Varilux Lens, Varilux Comfort, Varilux Definity, and Varilux Physio. This was great news for the eyewear industry because this lens was much more expensive than single vision or bifocal lenses, which meant more money for the companies selling them.
Optometrists regularly "prescribe" progressive lenses to people, using their influence with patients as a trusted doctor to prescribe healthy aids. However, progressive lenses do not provide any physiological benefit to patients - only cosmetic benefits - but they do provide much more money to optometrists.? Outside of the cosmetic benefits, progressive lenses offer the convenience of having distance and reading vision in one lens like a bifocal. Unlike a bifocal, however, the progressive lens also offer the mid-range and a continuous viewing area in the middle of the lens. On the negative side, progressive lenses have large areas in the patient's visual field that cannot be seen through, thus causing blind spots, and this can lead to headaches and nausea during the adaptation period (it takes time for a person to adapt his body and lifestyle to these types of lenses). Also, to use a progressive lens, the patient must learn not to move the eyes from side to side, but to move the head from side to side. At Eyeglasses.com, we urge patients to choose the right lens for their needs, desires, and pocketbook. In most cases, patients are more than capable of learning about eyeglasses, and making their own informed choices, along with advice from the eye doctor.
How Progressive Lenses Work
If you need vision correction for both distance and reading, then can use two pairs of glasses, and alternate depending on what you need to see. Or, you can choose bifocal lenses, trifocal lenses, or progressive lenses (called multifocal lenses). Many people find it convenient not to be required to remove their glasses and switch to another pair in order to read something. Multifocal lenses divide the lens so that part of the lens is for reading and part of the lens is for distance vision. Bifocal (two areas) and trifocal (three areas) lenses have visible lines that separate the different areas of the lens.
Progressive lenses, which are sometimes called no-line bifocals, are actually trifocal lenses without the visible lines. Progressive lenses were developed because many people wanted the convenience of not having to change their glasses to read, but they did not like other people to see the visible line.Also, with progressive lenses there is a continuous transition from one viewing distance to the next,so there is no large jump from near to far as there is in bifocal lenses.
Progressive Lens Design
Progressive lenses offer the convenience of multifocals, but without the visible line. However, progressive lenses are much harder to use and to adapt to than bifocal or trifocal prescription glasses, and they are much more expensive. In order to create a no-line progressive lens, there are two large areas of the lens that you cannot see through. Imagine what an hourglass looks like. This is the shape of the area of the progressive lens that you can see through. Objects seen through the areas of the lens to the left and right of the narrow middle section are highly distorted and you cannot see through them. The bulge areas at the bottom and top of the lens are for near and distance vision, and the thinner corridor connecting them is for intermediate distances. On either side of the narrow portion of the hourglass objects will appear blurry. In general, more expensive progressive lenses like Varilux lens have a wider corridor, and less expensive lenses have a narrower corridor that can restrict the viewing area considerably. On smaller lens sizes, it is necessary to slice off a portion of the bottom (reading section) of the lens in order to install the lens in the frame. As a result, the smaller the frame size, the smaller will be the reading portion of the lens.
Adapting To Progressive Lenses
In order to use a progressive lens, you must learn to move your head to see things; you cannot just move your eyes because you will be looking through a blurry part of the lens. This is called adapting to the lens. Most people can adapt within a month, but some people never adapt. It is common to experience dizziness and headaches during the time that you are adapting. Getting accustomed to progressive prescription glasses can be difficult, and you must have proper instruction by an eyecare professional.
Sometimes, people who try progressive prescription lenses for the first time have a difficult time learning to look through the appropriate portion of the lens at the right time. Often a simple fitting adjustment to your prescription eyewear by your local optical professional can make all the difference.
Fitting Progressive Lenses
To fit progressive lenses (and any multifocal lenses) properly, the eyeglass frames must first be fit and adjusted to your face. At this point, an optical professional measures the segment height of your lenses. He makes two dots on the lens, one at the bottom edge of your pupil, and the other at the intersection of the lower eyelid and your eye. The measurement in millimeters from the bottom of the lens up to each dot is the segment height. To make any multifocal lens, we must have an accurate segment height measurement. If you send us a pair of glasses with multifocal lenses in them, we can read the lens and determine the seg height and make a perfect copy (re-lensing your glasses). But that segment height is specific to each pair of eyeglass frames and cannot be used for a different pair of frames.
You can ask your local optical professional to measure the seg height for a pair of eyeglasses, and then send them to us with the markings on them. We can then make multifocal lenses. The next best alternative is to use our MFS.
Multifocal Fitting System
If you want to buy new eyeglasses or sunglasses with progressive lenses, or if you want to send us glasses without progressive lenses in them already, Eyeglasses.com can supply you with a progressive lens using our MFS (Multifocal Fitting System). Our MFS is a system that estimates how to mount the lens so that it will work for you. As a result, our MFS is not as accurate a fitting system as you would receive from a local optical professional. For some people, our MFS is not a good service, but you can still buy eyeglass frames at Eyeglasses.com and have the lenses installed by a local optical store. The MFS is a system that estimates your seg height. You have a conversation with our optical professional who will ask you questions about your experience with multifocals, the frame model you want to use, how you intend using the lens, and so forth. In the end, we are able to make a lens that works for about 85% of our clients. If we make a lens that does not work for you, we have a 100% return policy on the frames and the lenses. To begin this process, you must first have your prescription and pupillary distance "PD" measurement. Our optician will need this information in order to design the right lens for you.
Choosing An Eyeglass Frame For Progressive Lenses
There is only one major restriction on the kind of frame that will accommodate progressive lenses. The eyeglass frame needs to have a height of 30mm or more. Height is referred to as the B measurement of the frame, and is the inside measurement from the bottom to the top of the lens aperture in the frame. If you have fallen in love with a frame that has a B measurement of 27mm to 29mm, there are some new short corridor lens choices that may work for you. Contact Eyeglasses.com customer service for more information.
We strongly recommend that you fax your prescription to us. We can read your prescription and then help find the best prescription eye glasses lens for you. For multifocal lenses and progressive lenses orders, we require that you fax your prescription to us.
About Your Prescription
Prescriptions have a certain format that is always followed. The first line of your prescription is always for the right eye, sometimes designated the OD. The second line is for the left eye, sometimes designated OS. The prescription for each eye is divided into Sphere, Cylinder, and Axis values. It is common to have no values for any one of these, in which case you might see the letters PL or plano, or to have values for all of these. Sometimes the prescription may say OU which means both eyes.
If your prescription is for bifocals or trifocals of progressive lenses, there may be additional information on the prescription that says for example Add +2.50. This is important information if you are ordering reading or multifocal lenses. The numbers are expressed in diopters that tells the power of the lens. A diopter is a value that is metric and universal worldwide.
On a prescription for multifocal glasses lenses, you will see information designated as add power. Your add power is simply the magnification that is added to your sphere value for distance vision, in order to create a field of view for reading. For example, if your sphere value for distance viewing is 3.00, and your add power is +2.00, then your near vision correction is 1.00. Or, if your sphere value for distance viewing is +1.00 and your add power is +2.00, then your near vision correction is +3.00.