Bifocal Glasses

Bifocal is a kind of glasses that were developed to offset a common vision problem among presbyopic wearers. Bifocal glasses have to be equipped with two focal points. Presbyopia was a common vision problem to those people who were going to fifties or becoming older. This visual problem caused a difficulty in seeing close up objects. People often call this eye problem:” too short arms”, this common phrase describe this symptom vividly. Why they called this? This is because presbyopic patients are used to hold the reading objects at an arm’s length, in which position can they see clearly. The need for bifocal eyeglasses is still driven by another visual problem, either nearsightedness or farsightedness. Some presbyopic patients have got farsightedness or myopia at an earlier age. Without the help of bifocal glasses, they have to use two separate pair of prescription glasses. That is really inconvenient if they have to make visual switches between different ranges.

Although a lot of wearers adore bifocal glasses and sing the praises of this kind lenses, in fact this entity is far from perfect. Certain defects have been reported on those visual aid devices. Commonly heard ones include headaches, visual dizziness and image jump. What is the reason for these unwanted problems associated with bifocal eyeglasses? In most cases, factors of fashion will not cause problems that are associated with lens function. Those symptoms or side effects are closely linked with visual experience. So, it is the lens design that matters and leads to these bothersome or disappointing problems.

Franklin bifocal is the first bifocal eyeglasses design. He developed bifocal glasses in 1784. But now this lens has different designs. Franklin bifocal added reading segments in different shapes into a primary lens. Reading parts usually account for a small portion of the whole lens. But this kind of design could lead to a problem which just mentioned. Because there is a crossing line on the bifocal lens and it will cause frequent image jump. Headache and dizziness are actually subsequences of image jump that occurs from time to time. Bifocals with reading segments have a similar situation. It usually takes a period to adapt to bifocal spectacles. PrescriptionGlassesOnline.net is the emerging online eyeglasses store selling high quality prescription glasses, such as single vision myopic glasses, reading glasses, bifocal and progressive eyeglasses etc. prescription sunglasses with RX tinted lenses. PG guarantees lowest possible price in the market. PG’s return and refund policy makes any purchase risk-free.