The first time I put a pair of glasses into this cleaner, I was also a little disappointed. But maybe it was my high expectations, because my last ultrasonic cleaner "diffused" years ago :-o, and I remembered perfect vision.
Anyway, our Velleman also makes an astonishing amount of noise, considering that it says "ultrasonic" on the package. We tested it with some jewellery the daughter found on the side of the road. It looked as if it had come from a Terence Hill film. After cleaning, it sparkled again. The glasses should also be transparent again after cleaning, but as far as I know, ultrasonic cleaners do not remove large dirt and grease deposits.