The clear, jelly-like tissue in the center of the eyeball is called vitreous humor, or simply vitreous. Some problems in the eye can be helped by removing this tissue. In young people, vitreous rests snugly against the retina, and as the body ages, the vitreous can liquefy in parts and undergo involution, such that the edges will fall in towards the center of the eye. The occasionally exerts traction on the retina resulting in a tear or even retinal detachment. If the detachment is severe, removing the vitreous may be helpful for reducing vitreous traction.

Diabetic retinopathy is also sometimes helped by removing the vitreous, since the this tissue appears to facilitate the growth of abnormal blood vessels in these patients.

Patients with uveitis often benefit from removing the vitreous also, for two apparent reasons. It seems to be the case that, in some patients, vitreous provides a stimulus for ocular inflammation. At the very least, ocular inflammation is generally easier to control in patients whose vitreous has been removed.

Vitrectomy is major ocular surgery, peformed in an operating room. Patients receive a local injection to anesthetize the eye, or even general anesthesia, and the pupil is dilated with drops. Under an operating microscope, three holes, or "sclerotomies" are made in the eye in most cases. An instrument is used to cut up and draw out the vitreous through one sclerotomy, while fluid is infused into the eye through another sclerotomy. The third sclerotomy generally is used to hold a light pipe, which illuminates the inside of the eye so the surgeon can see what is happening.

The eye is patched after vitrectomy, and patients often stay in the hospital for one night. The doctor removes the patch the next day, and a recovery period of several weeks is anticipated.