Word for eyeglasses with no prescription
The term used by optometrists, opticians, and similar professionals for the 'lenses' that perform no refractive function is plano (in Latin, planus means flat). The term is, however, unlikely to be readily understood by the general public.
The common term for this is simply non-prescription glasses.
From "The Benefits of Non-Prescription Glasses" by Priya Modi at Classic Specs:
Many of us can recall our memorable days of being made fun of in elementary school for wearing glasses. (Does “four-eyes” ring a bell?) Luckily for you, things have changed since then, and we are onto a new chapter in our lives where we now have a positive relationship with the glasses we wear every day. Nowadays, glasses give wearers a bold look that creates a fashion statement which enhances your overall appearance, rather than taking away from it. Different styles and frames can complement your outfit whether you’re running errands or at the office in heels. Sometimes, we all need a break from wearing contact lenses in our eyes so the naked eye can have more oxygen. However, people, regardless of their vision, are starting to wear them just because it looks good. These are called non-prescription glasses and there are more benefits than just fashion or a simple desire to wear. Below are some benefits of non-prescription glasses.
From Wikipedia's entry on glasses:
Much like other fashion designs and accessories, eyewear is created by designers, has reputable labels, and comes in collections, by season and designer. It is becoming more common for consumers to purchase eyewear with clear, non-prescription lenses, illustrating that glasses are no longer a social stigma, but a fashionable accessory that "frames your face."
Even more colloquially, people will refer to them as fake glasses or clear glasses.
From Cosmic Eyewear:
Here you'll find one of the largest, budget friendly & best selections of clear non-prescription (glasses without prescription) optical quality designer fake reading eye glasses to match your personality, fashion or style statement! Shop affordable accessories & hundreds of clear glasses for men & women.
And people in theatre or film might even refer to them as prop glasses, especially if they are only frames without lenses at all. (However, prop is a generic attributive noun for any number of items and accessories.)