Many people are talking about or heard about bifocal specs. I am wondering whether they know there are actually two kinds of bifocal specs: progressive bifocal specs and traditional bifocal specs. What’ their difference?
Progressive bifocals are different from traditional bifocals. The former type can offer wearers contemporary appearance, while the latter one can do nothing about that. This is because traditional bifocal lenses have visible segment lines separating the two lens powers. These lines constantly suggest that the wearers are elderly. In contrast, progressive reading glasses free from those lines enable wearers to be cosmetically younger. Vision correction provided by them is more natural.
When it comes to basic vision correction, both the two bifocal specs can correct for multiple viewing distances. In this sense, these glasses are called multifocal reading spectacles. Well, this is almost the only common point between them. Differences account for the majority. First of all, progressive reading glasses are capable of providing uninterrupted central vision while bifocals can not. This difference originates from different lens designs. As mentioned before, progressive addition lenses are made with a continuous, gradual power change from the bottom to the top. But bifocal lenses come with only two separate lens powers, so that the vision transition at the boundary of the two powers will certainly be interrupted. By taking such a complex lens design, progressive reading spectacles can eliminate the problem of image jump caused by traditional bifocal glasses.
I will introduce more about progressive bifocal specs. In the eyeglass lens industry, the most advanced and complex lens type is very probably progressive additional lenses (PAL). These lenses are sometimes called progressive addition lenses, varifocal lenses or just progressives for short. Using progressive addition lenses, manufacturers make progressive bifocals or progressive trifocals available. The most significant breakthrough made by progressive addition lenses is that they offer a continuous, gradual change in the power strength from the lower to the upper portion. Following the traditional approach, the reading correction is provided at the lower section while the distance correction is placed at the upper part. This article tries to make a comprehensive comparison between progressive glasses and bifocals.
When you decide to buy a pair of bifocal specs, you have also need to decide which kind of bifocal specs you need, progressive bifocal specs or just traditional bifocal specs.
