Vitreous humour is the clear gel that fills the eyeball, lying between the lens and the retina in the eye.

Floaters are small, generally harmless, defects in the vitreous humour.

Where the vitreous humour has become cloudy, vitrectomy is surgery to restore sight in which the surgeon removes cloudy vitreous humor in the eye and replaces it with a salt solution. Vitrectomy is generally not indicated unless sight has already been severely affected, as the operation itself can cause blindness.