Prescription Lenses: How Glasses are Made
Find out how an eye test leads to the frames on your face!
You’re at your regular eyecare professional, getting new prescription glasses. They tell you your new eyeglass lenses will take a few working days to process before you can collect them.
This leads you to wonder: Why does it take so long?
No doubt you’ve wondered before how glasses are made, especially when you can’t collect your new eye wear immediately!
As it turns out, a lot more work goes into a pair of eyeglasses than just a piece of plastic or glass inserted into eyeglasses frames.
See a whole new world with the knowledge of how corrective lenses are made!
Keep on reading to find out how prescription glasses are created and how far they’ve progressed.
A Brief History of Eyeglass Lenses
Invented in the early 1200s, the magnifying glass was the first optical lens for people with poor or declining vision.
To make those eye glasses, natural materials like transparent quartz and beryl lens were used.
Seeing the increasing demand for prescriptions glasses, Alessandro di Spina made more complex lenses and marketed them to the entire public.
These new lenses were the concave lens and convex lens.
The convex lens was used in eyeglasses to treat farsightedness, while the concave lens corrected near-sightedness.
Further advancements following those two lenses led to the first optical prescription glasses for astigmatism, as well as the bifocal lens.
To cope with this increased demand, quartz and beryl lenses were replaced with glass lenses.
Glass lenses were the most common material used for corrective lenses before the introduction of plastic lenses in the 1950s.
Meanwhile, plastic lenses make up more than 80% of all eyeglasses worn today.
Plastic lenses quickly gained popularity among those who wear glasses as a lighter, less prone to breakage, and more comfortable option.
Glasses currently come in a wide range of styles, colours, and sizes, making them nearly as much of a fashion statement as they are a need.
Despite plastic eyeglass lenses being the most common form of spectacles now, it is a wonderfully efficient product borne of impressive feats in engineering and craftsmanship over the years.
How Modern Corrective Lenses Are Made
Getting an Optical Prescription
Glass lenses were gradually replaced with polycarbonate lenses in the mid-1900s, making modern prescription glasses extremely lightweight, durable, and more widely available than they were centuries earlier.
Your Eye Guardian is pleased to let you know that we have a hand in creating your eye glasses!
The lens making process begins in an optometrist’s clinic when patients receive an eye test to ascertain their prescription.
The following values are included in an optical prescription:
- Axis – a number between 0 and 180 degrees that indicates the orientation of astigmatism
- Spherical base strength – A negative or positive value that measures nearsightedness or farsightedness
- Cylinder base strength – A negative or positive value that measures the degree of astigmatism
Each lens will be ground, bevelled, and edged to the shape and size necessary for enhanced vision based on the patient’s prescription.
Lens Blank Crafting
Most glasses begin with “blanks,” or circular pieces custom-made by optical laboratories. They are made of polycarbonate plastic or glass about the size of a coaster.
Depending on how much assistance your eyes require, these lens blanks have different front curves and thicknesses. Thus, it’s critical to double-check dimensions for prescription placement so that your lenses and you can see well.
The lab technician selects a blank that is the most similar to the patient’s prescription and feeds it through a machine.
Using a lensometer, the blanks are marked at the “optical center,” which refers to the exact position over the patient’s pupil. Then, each lens blank is affixed with adhesive tape to prevent them from being scratched during the grinding and blocking processes.
After the tape is in place, a blocker made of heated lead alloy is added. The blocking process involves locating the optical center of the glasses lenses to achieve the optical strength they require.
Finally, the blanks are placed in an edge grinder where the flat side of the lens is ground into the proper shape.
The technician now polishes the lenses to perfection with a fining machine and other materials such as soft sandpaper.
During this phase, the block and tape are also manually removed and lenses sterilised.
After a few coats of UV treatment and tints, the lenses are ready to be inserted into the eyeglass frames!
Even though the procedure is meticulous, new technology allows opticians to create lenses swiftly and efficiently.
During the manufacturing process, several quality assurance steps are in place to ensure that patients get their exact prescriptions.
Four essentials are:
- Examining the surface for scratches, chips, and splits.
- Ensuring that the prescription is entered appropriately into each machine.
- Checking to see if the optical centre is properly marked.
- Checking the optics while the lenses are in the lensometer.
Functionally, glasses frames are intended for holding the optical lens on the user’s face.
However, many of us who use glasses love getting frames that show off our personality!
The broad range of glasses frames out there on the market may leave you spoiled for choice.
If you’re indecisive, think about it this way: plastic or metal?
High index plastic frames are fantastic if you’re looking for something colourful, while the latter is ideal for malleability and strength.
If you find your current frames constantly slipping, opt for new frames that have rubber nose pads.
Regardless of the type of frame you choose, it all begins at the frame maker.
After a material is chosen, it will be shaped to the specified frame fronts using a lathe. Meanwhile, the temple pieces, or frame arms, are carefully cut.
The frames are then gently smoothed out in a tumbler loaded with soft abrasives.
Once smooth, the frame arms are heated along with several pieces of wire-thin steel. These wires are inserted into the arms for structural integrity.
Following that, tiny hinges are expertly installed to secure the temple pieces to the frame fronts. The parts are secured using minuscule screws.
Finally, the frame arms are moulded to fit over the ears.
The final product is polished before a final check to verify whether the spectacles are balanced and secure.
Looking for prescriptive lenses?
From your eye test to the final eyeglasses, the process of creating a pair of prescription glasses requires precision and expertise.
After all, a good pair of glasses is set apart by the skill that went into their production.
Get quality and professional service from Your Eye Guardian!
We care for you and want to help you achieve the perfect vision you deserve.
Contact us now to schedule an appointment!