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 it comes to basic vision correction, both progressive bifocals and traditional bifocals 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.

Progressive bifocals differ from traditional bifocals in another aspect. 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.

C: Progressive bifocals and traditional bifocals differ in mainly two aspects. One is uninterrupted central vision and the other is contemporary appearance.

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