Open this fluorescent light fixture?

If you do have to get inside, remember the saying "lefty loosey, righty tighty" for unscrewing or tightening things. I'd try turning it counterclockwise 1/4 turn (left) to see if that piece snaps into some inside slot and then is turned right to tighten it.

From googling the image, I think those are "light fixture retainer clips" but they aren't the same shape as what's online. Try squeezing the top parts together to see if that releases them.

https://www.google.com/shopping/product/12610015078724930727?q=fluorescent+light+fixture+parts&newwindow=1&rlz=1C1SQJL_enUS800US800&sxsrf=ALeKk02ryu2Km5-5w4Hajjq2MTd83RdBzQ:1587308449562&biw=1280&bih=913&prds=epd:17761806232732065866,paur:ClkAsKraXxWEh22l_XiNdjFtpljm4DuW4sey7imwoq06F2Mvt0BUyM2oINMG8Ofg-OCxya2I49hXYk5KhPqTv0Q0c1C28bfhLv8_QXW1-f2WKUaa5DgJ3KTvZhIZAFPVH736JMJ8ZuFWwH-DXvj2hKS6EB7l9Q,prmr:1&sa=X&ved=0ahUKEwjUz9nm4PToAhVNgK0KHcGMCmYQ8wIItAM

If you are attempting to remove the fixture completely, you could pull on those clips to straighten them out so that piece can be pulled down.

Have you closely examined all other areas to see if there are visible screws anywhere else?

My final, best suggestion is to take that pic to a lighting supply place (AFTER covid stay-at-home orders please!) to find the answer. 😎

Use a pair of pliers and squeeze the too ends together and pull them out. They clip on the inside of the hole.

Often there are small clips that slide to the right or left holding the lens in. Look along the edges to see.

If you squeeze the ends (hand or pliers), then the little ears that fit into the hole will be able to disengage from the fixture.

thanks all! I'll give it shot in the morning.

Is this what you are looking for https://www.youtube.com/watch?v=P6MzfSY7iF8

Hi! I also think they squeeze together. Good luck and stay safe!

This is not a very good picture you realy can’t see it and the edges were it would open