A Brief Introduction Of No Line Bifocal Eyeglasses

Bifocal reading glasses were first created for presbyopic individuals with an additional vision problem to see both distances clearly

. However, there are noticeable problems caused by the use of regular bifocals. For instance, image jump will happen while making visual switches. And subsequently dizziness and headache will be caused during the adapting period. Some wearers are even unfortunate enough that they can never get themselves adjusted to bifocals. This bothersome shortcoming of bifocal reading glasses then called for the development of no line bifocal eyeglasses. This new form of bifocals has some other names, like progressive spectacles, progressive additional glasses, progressive power glasses and graduated prescription eyeglasses and the like.

In fact, both regular bifocal eyeglasses and no line bifocal eyeglasses belong to the category of multifocal glasses. While ordinary bifocals can only deal with two visual problems, no line bifocals are capable of correcting presbyopia and other disorders of accommodation. While an ordinary bifocal lens has solely two powers, a progressive lens is characterized by a gradient of increasing lens powers. It is this added power gradation that helps solve other refractive errors. With a regular design, the power gradient of a progressive lens starts at the top of the lens with a distance prescription and reaches at the bottom of the lens with a maximum addition power.

This natural design provides a highest degree of distance vision provision at the top edge and a maximum amount of reading aid at the lowest edge. When it is possible to figure out the exact number of powers molded in a bifocal lens or a trifocal lens, it is impossible to carry out a similar task in a progressive lens. As a result, one problem is that what a power gap can be achieved in a single lens. In fact, the length of the progressive power gradient depends mainly on the refractive index of the lens. In most cases, the power gap ranges from 0.75 to 3.00. Prescribing a pair of no line bifocal eyeglasses, the wearers visual condition and age will be considered.

C: No line bifocal eyeglasses were aimed to succeed regular bifocal reading glasses which have obvious shortcomings. Progressive eyeglasses do a better job by providing a gradient of prescription powers.

by: Anderson

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