The phrase "eyes dull" is correct and usable in written English.
You can use it to describe a person's tired, lifeless appearance, often when they are feeling unwell or overwhelmed. For example: "Compassion was evident in her eyes, which were dull from the stress of the situation."
She lunged at me, in her splendid nakedness, knife and all, her eyes dull with the chill of empty space.
And the laughs keep coming, even as the light dies, her face turns grey and her eyes dull like a corpse's.
His face is pale, his eyes dull, and his ragged clothes are covered in dust as if he has been the victim of some calamitous accident.
In the dreams, her mother is alive again, but she is suffering as she did on her deathbed: desperate for morphine, her eyes dull, her mouth dry and hanging open.
"Cherry looked about 30 years older than he had when he had set off, his cadaverous face scarred and corrugated, nose dark, eyes dull and hands white and wrinkled.
The wiry, bright-eyed comic in the lobby was replaced by a heavyset man whose face had been eaten away by weariness and fear, his eyes dull, the barest flicker of light left in them to suggest his soul was still alive way down inside.
But rather than smiling proudly at the institution he inspired, Sutti merely looks on forlornly, face motionless, eyes dulled.
As he tells his stories of unspeakable inhumanity, his eyes, dulled by age, well up, and he gently dabs his tears.
Her face was as gray as her real hair must be, drawn in grooves of gravity and gravitas, eyes dulled to nondescript, and when she cracked a small smile to the blind (really) person next to her, her teeth bore witness to a long acquaintance with Liggett & Myers.
The way his eyes, his sky blue eyes, dulled and rolled to the back of his head while they were still open.
I looked then, and the woman was now cornered, and she averted her eyes from her abuser and I could see that her eyes dulled and she looked disconnected.
