1. Removal of the gel (called the vitreous) from within the eyeball. 2. The microsurgical procedure of removing the vitreous humor and replacing it with saline solution; performed to improve vision that has been impaired by opacities.
3. Removal of the whole or part of the vitreous body in treating endophthalmitis, diabetic retinopathy, retinal detachment, intraocular foreign bodies, and some types of glaucoma.

Surgical procedures which may be used as part of modern vitrectomy surgeries

• Membranectomy: the removal of layers of unhealthy tissue from the retina with minute instruments; such as, forceps (tiny grasping tools), picks (miniature hooks), and visco-dissection (separating layers or tissue with jets of fluid).
• Fluid-gas exchange: the injection of gas into the eye; such as, sulphur hexaflouride or perflouropropane to hold the retina in place or to temporarily seal off holes in the retina. These gases disappear spontaneously once they have accomplished their purpose.
• Silicon oil injection: filling the eye with liquid silicon to hold the retina in place.
• Photocoagulation: a laser treatment to seal off holes in the retina or to shrink unhealthy, harmful blood vessels which grow in some diseases; such as, diabetes.
• Scleral buckling: the placement of a support positioned similar to a belt around the walls of the eyeball to hold the retina in a proper, attached position.
• Lensectomy: removal of the lens in the eye when it is cloudy (cataract) or if it is attached to scar tissue.