The popular statement glasses were usually retro or king-sized with a heavy plastic rim in black or tortoiseshell plastic.
This summer white, red and even blue frames were appearing on faces.
"Guys don't have as many accessories to take really so I think it has become a big statement for guys as well really," she said.
Advertising agency DDB HR administrator Nathan Jeune-Manning, 23, began wearing plainos about four years ago after he got his eyes lasered and his face felt "empty" without spectacles.
"So I kept my frames and got the lens removed, but it turned out it became trendy and became quite a cool thing to do so it worked in my favour ... I wear them all the time unless it is really really sunny and then I will chuck on some sunglasses."
Mr Jeune-Manning had been told he looked smarter with them on and chose to wear ones that were in fashion.
He knew quite a few people who wore non-prescription glasses and said his flatmate had even worn them to job interviews.
"He definitely would do it to appear a different way, ie more intelligent."
OPSM optical buyer Joanne Pereira said this year had been the most popular year for plainos so far and some people were even converting sunglasses to optical glasses to achieve the over-sized geek chic look.
"They [younger shoppers] feel that wearing glasses makes you appear more studious or intelligent ...
"It's even part of that whole trend piece, so glasses are now a fashion accessory so they're not simply something you use as a medical device, they are seen as an important function."
Making a spectacle
Justin Bieber
Zac Efron
Alexa Chung
Johnny Depp
Christina Hendricks (right)
What's in trend
Thick plastic rims
King-sized glasses
Bold colours
Geek chic and retro styles
