Bifocals were originally made by cutting two lens segments (one for near vision and one for far vision) and attaching them together into a single lens.
Here's a breakdown of the original process:
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Identifying Vision Needs: The process starts with understanding the individual's near and far vision prescriptions.
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Lens Preparation: Two separate lenses are crafted according to the determined prescriptions—one correcting for distance vision and another for close-up tasks like reading.
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Cutting the Lenses: The distance lens is cut in a specific way to accommodate the near vision lens segment. The near vision lens segment is also cut to fit precisely into the space prepared in the distance lens.
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Assembly: The near vision segment is carefully fitted and attached to the distance lens. Benjamin Franklin, the inventor, originally achieved this by physically joining the two lens pieces within a frame.
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Smoothing and Finishing: The combined lens is then smoothed and polished to eliminate sharp edges and ensure comfortable wear. The lens is shaped to fit the eyeglasses frame.
While the original bifocals involved physically joining two separate lenses, modern manufacturing methods have advanced significantly. Modern bifocals are often created through a molding process or by fusing different lens materials together, creating a seamless transition between the near and far vision correction areas. This makes them more aesthetically pleasing and comfortable compared to early bifocals.
