The History Of Spectacle Manufacture
Ever wondered how glasses are actually made? Read on to find out how!
A Short History
Ever wondered how glasses are actually made? We all know they’re a pretty marvellous invention, with many of us relying on them on a daily basis.
Early recorded evidence demonstrates that glasses first appeared near Pisa, Italy about the year 1286.
Of course back then, we knew little about the causes of visual defects and how to correct them. Back in earlier times, frames were made from any material people could source to hold a lens: wood, stone etc.
Glasses lenses were made of, yup you guessed it… glass! (Up until fairly recently in fact).
Nowadays we tend to use plastic lenses as they are much harder wearing, more durable, lighter in weight and are less prone to chipping/cracking (no one wants a cartoon style smashed pair of glasses in a million tiny pieces!)
In earlier days, lenses were ground, by hand, into the spectacle frame. These days, with most Optical practices making hundreds of pairs per day, hi tec machines are used to do this for us:
It’s not as simple as just pressing a button, a lot goes into the process, but this machine makes things a lot faster.
The machine has a ‘tracer’ which is like a little plastic arm which traces the inside rim of the frame. This shape is then saved into the machine’s settings and the grinding wheel cuts the lens to that specific shape.
Without getting complicated – depending on whether a person is long or short sighted, a lens, in either a curved or a flat shape, is used to refract light in the direction needed to help light focus on the retina (the bullseye to great vision AKA the target!)
Depending on the severity of the visual defect, the lens can vary in its power, ie a low or a high prescription. The higher the prescription, the steeper the curve of the lens, as it will need to bend the light more.
A spectacle lens comes in a round disc, uncut, and looks like this:
This is a glazing machine. The computer within the machine, traces the shape of the frame to be used, and the grinding wheel then cuts the lens to the correct shape. The machine uses water to remove excess lens material/dust and usually takes a couple of minutes per lens:
A lab technician will be highly trained in the use of these machines and will also need to enter specific measurements relevant to the patient’s pupil distance and height. Various techniques can be used in ensuring the lenses are tailored to each patient’s needs.
The finished, cut lens is inserted into the frame by hand and the quality of the frame and lenses checked before being dispatched to the spectacle wearer:
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