Michael John Pickering's poem is a light, funny complaint about eye floaters, those drifting specks that cloud your vision. The speaker imagines his floater as a "dirty little fly" that has moved into his left eye ("sinistral" is an old, fancy word for left) without being invited. He treats it like a rude houseguest who has settled in and refuses to go.
The speaker feels irritated but also amused by his own predicament. He snaps "Use your imagination!" when asking why he doesn't want it, as if the answer should be obvious. He adds that floaters "rot, but do not die" and dance in bright light, as though they were putting on a show he never asked to see. Then he politely begs for sympathy from others who suffer the same thing.
The mood is playful and wry. The tight, repeating rhymes and the way the opening lines return at the end mirror the problem itself: the fly keeps circling back and can't be shaken off.