Cone shaped blur around edges of iMac monitor - WTF?

Question

Monitors

Comrades,
please help, tell me what the problem is?
A 2011 iMac monitor has strange cone-shaped blurring on the top left and right edges of the monitor. The image in these areas becomes noticeably blurry.
Seen in the picture:

The monitor is off. Of course, I wiped it. That is, this is not dirt or bugs with graphics.
Who faced such a problem?
What is its reason?
How can you decide?

Answer 1

Aimak disease
has been discussed many times both on Russian and foreign boards
option 1 - Moisture. For example, because of air humidifiers, or if your aimak is in the basement of the house =)
option 2 - dust or, as they say, soot - disassemble and clean, or if there is still a guarantee - carry it in warranty. this jamb is recognized as apples

Answer 2

You apparently have dust / soot on the protective glass itself from the inside. It's easier, remove the glass and wipe with microfiber. And it often happens that such soot appears inside the matrix itself, in layers. Then blackouts will be visible on the included white background. This is already more difficult, it is necessary to disassemble the matrix. This is an aimak disease, the matrix is ​​leaky and dust gets inside. To reduce this process, it is necessary to periodically disassemble the aimak and clean the radiators and cooler from dust.