imac screen problem?

The iMac has a glass over the screen. You see the dots on which surface ? Outside of the glass or really on the screen ?

Few years agor it was a known issue to have some grey dirt on the screen and Apple replaced some screen.

If the iMac is still on garanty I would show it to a Genius Bar.

Can you post a picture ?

If it is outside on the glass you can clean with relativ strong energy. But not too strong. Even a small amount of liquid https://discussions.apple.com/thread/722009?answerId=3493259022#3493259022.

From my understanding you have some type of (dots) iregularities being displayed on your screen. The way that Apple iMacs work are a LED Screen, empty space, then glass. This is why your iMac screens look glossy cause of the glass.

If you ever see tiny red or black or white dots on the screen when its turned on there is a simple test you can do to see if its actually the LED screen itself, and those dots would just be dead pixels. Change your screen color from white to black to red to green and see if the dots remain. If so then you may have dead pixies and in need of a screen replacement. "but since you said you still see the dots once the monitor is turned off I'm guessing this is just dirt or dust on the glass. outside or internal.

If you think the dots are on the glass take glass or screen cleaners and wipe down the screen and see if that solves the issue. If you do this and you still see those iregularities it could be two things. They could be small chips of glass or scratches in the glass of the screen, or there could be dust or dirt on the inside part of the glass, which could happen if the people who installed the glass cover over the screen where in a dusty environment. This is why I urge people to never use dust sprays to clean anything with a glass cover, cause you could be blowing dust behind the glass onto the actual LCD or LED and its hard to get it cleaned once sealed.