In the early days of antique eyeglasses, frames were seen as a medical device worn by those who needed this "crutch". Much attention wasn't given to color, fashion, and design. Vintage frames were generally gold or silver tone, and the designs round oval or ovid (AKA Ful-Vue Glasses). While there were many solid gold glasses, this was more of a difference in material vs a difference in style
Furthermore, plastic (zyl) wasn't considered for the use of vintage eyewear at this time. There were some inexpensive drug store eyeglasses or sunglasses made of plastic but it's widespread use hadn't yet begun.
The word zyl used in early vintage frames is shorthand for zylonite, short for rezylonite, the official name of the material. During WWII Plastic was tweaked to be suitable for use in many products previously made of various metals, Thus began the widespread use of plastic in 1940s, and mainly, 1950's glasses.
The use of plastic introduced many new opportunities and styles to vintage eyeglass frames. Firstly, color. Plastic vintage glasses could be made in any conceivable color or combination of colors, something not possible in earlier antique frames.
But just as important as color, if not more important, was style. Gold or silver eyeglasses with their thin metal wire did not have a character or personality of their own. It was more of a minimalist look that accentuated ones own features rather than creating a style of their own.
Vintage Designer Eyeglasses
Another factor happening at the same time was the introduction of the word "Designer" into eyewear. Today almost every frame that comes out is designer. While it is no secret that most of today's designers are, essentially, designing frames for 1 or 2 big eyeglasses manufacturing monoliths rather than manufacturing them on their own, this itself is unique as it was not always this way.
Throughout the 1930s and 1940s eyewear manufacturers in France and Italy started collaborating with Fashion designers in order to market their vintage glasses frames. These vintage frames were getting imported into the US and were getting popular. The first American Designer vintage Eyeglasses started in 1952 when American Optical started working with Designer Elsa Schiaparelli, an extremely popular fashion designer from Paris, creating the Schiaparelli eyewear Collection, a beautiful collection of close to 100 vintage eyeglass frames with various styles and ornamentation. each Frame was given a fancy name such as "fireworks" , Women Of The World" etc. Many had real pearls and diamonds and cost thousands of dollars.
At around this period you had the introduction of Tura cat eye glasses into the scene, adding further adding color and style into a once boring world of antique eyeglasses and creating the world of eyewear as we know it today.
All these factors coming together created the explosion of style in Men's, but mainly, Women's vintage eyeglasses