It is believed that eyeglasses first appeared in Italy in the late 1200’s (not long after the invention of the magnifying glass) and took the world by storm. After centuries of individuals observing an anomaly of one’s visual perception looking augmented or larger through the surface of water or curved glass; it became apparent that harnessing this phenomenon could be used to enhance and correct vision in the form of the artificial lens.
We say artificial because lenses occur naturally as well, seen in places such as eyeballs. Any kind of lens works the same way in that it augments and manipulates light, focusing and refracting it differently based on the curvature or angle of the surface. Some lenses can make things appear larger at certain distances, while some lenses may actually do the opposite and flip an image or perspective around altogether.
Eyeglasses are the result of how we have evolved the use of lenses in order to correct a number of conditions which effect the human eye. “Glasses” are worn on the face, usually resting on the nose and ears while holding lenses in place over the eyes. We have improved upon our initial observations and developed a number of different eyeglass lenses for different conditions. In some cases, we also create hybrid lenses to allow for the functionality of multiple kinds of lenses, as seen in bifocal, trifocal and varifocal lenses.
Early lenses were created using naturally-occurring quartz and beryl, however this was replaced by glass (which we associate the name with) and today most eyeglasses are manufactured out of polycarbonate plastic. In general, glasses are commonly produced commercially and not considered something people can create at home. While the principle is simple in that you grind and shape a piece of glass or plastic to maintain concave or convex curves; the degree of detail requires precise machining for various angles and surfaces. Far from a “one size fits all” scenario, lens types vary greatly based on the degree of an individual’s condition and which condition they have to begin with. No matter what, you will need to know how to determine what condition that is, as well of the severity of how it effects one’s vision.
Today the easiest way to obtain glasses is to buy them. Automated machines also exist which can create lenses from “blanks” based on the needs and prescriptions of individuals who require corrective eye wear.
In a world where you can no longer go to the store and buy glasses, your best bet will be scavenging for what works best, or obtaining/coming across the tools required to identify conditions and prescriptions such as an autorefractors, lensmeters and a slew of other machines for grinding, surfacing and even coating.
Autorefractors (or automated refractors) are computerized machines that can measure how light is changed when it enters a person’s eye. The device uses information from this process to calculate the severity and type of one’s refractive errors and offers a lens prescription.
Lensmeters (or lensometers, focimeters or vertometers), measure and verify the prescription of lenses such as those found in eyeglasses. They can be used to identify the power and prescription of manufactured glasses if they are not otherwise marked. Today we have automatic lensmeters, while pre-computerization we used manual devices.
Making eyeglasses can be complicated, but if you need to produce them you can find a substantial number of CNC (computer numerical control) machines and grinders to actually produce lenses and lens blanks from blocks of glass or plastic. Beyond this there are also purpose-built, commercial grinders/generators/surfacing machines which cut lens blanks to fit into specified frames.