"well-trained eye" is correct and usable in written English.
You can use it to describe someone who has been trained to recognize certain features or qualities from a quick glance. For example, "The art curator had a well-trained eye and could easily identify a genuine painting."
A well-trained eye and ear — emphasis on the well-trained — can pick up signals a metal detector cannot.
Recently, the architectural tree caught the well-trained eye of Neil Hendrickson as he walked the property.
People who knew Ghiya say that although he lacked Sharma's well-trained eye, he made up for it by amassing a vast inventory.
And Eula's sense of style, especially the suits he wore, must have been a beacon to Davis's hungry, well-trained eye.
Most times it was just a stray goat or some other straggly creature trying to find something to eat amongst the dry scrub and brush of Afghanistan, but to Liam's now well-trained eye, it was something more.
Experts such as Tancred Borenius, "a flamboyant Finn of part-Italian descent", would gauge potential sales with their well-trained "eye", while "The Flying Squad" would scour the obituaries for news of a death that would set them speeding across the country to secure for their salerooms the contents of one of the grand country houses.
"Animators have well-trained eyes," Catmull said.
Even as Mr. Poneman tracked the action, a recruiter from Purdue, a local basketball legend, and a former Foreman coach who has since moved to Niles North High School all passed — very noticed — before Mr. Poneman's well-trained eyes.
Interior designers are sometimes called on to confer a sheen of taste where it would otherwise be lacking, but Mahdavi's clients — the fashion designer Alber Elbaz, the pharmaceutical heiress and arts patron Maja Hoffmann — tend to have as much culture as they do money, and to use her as a lens to focus their already well-trained eyes.
Kalahari truffles are the cheapest of the bunch (at least 100 times cheaper than their European relatives), and in Namibia, truffle hunters don't require the aid of dogs or hogs -- only their well-trained eyes.
Suddenly, a three-star alarm reverberates in my well-trained ear, my eyes dart to the monitor, and instead of normal heartbeats passing on the screen, I see a wavy line indicating someone's heart is about to stop.
