The jelly-like substance called the vitreous fills the eye. The vitreous is a gel that maintains the shape of the eye, supplies it with nutrition and helps with the focusing of light.
The retina is a thin membrane located in the inside of the eye, adhered to the wall of the eye like "wallpaper" and that acts like the film of a camera, capturing the image that will be transmitted to the brain through the optic nerve.

Vitrectomy

Is an operation that is sometimes required to remove the gel or vitreous humour that is located inside the eyeball. This microsurgery is carried out though three tiny holes in the white of the eye (sclera). This operation is used commonly for:

• Retinal detachment surgery to reposition the retina.  The vitreous jelly of the eye is removed, the retinal tear(s) causing the detachment are treated with laser and a gas (or occasionally oil) bubble placed inside the eye to lift the retina into place.   In some cases scleral buckling surgery is performed: after freezing treatment of the tear (cryotherapy), a plastic explant is sewn on surface of the eye. This creates ridge inside the eye to close the tear. RCOphth Information for patients
• Macular hole surgery, in this condition the macula develops a hole leading to loss of central vision. This can be treated by vitrectomy and inserting a gas bubble which remains in the eye for about 4 weeks. The gas bubble floats in the eye and pushes on the hole producing hole closure and improvement of vision (see pictures below using OCT retinal scanner before and after surgery).
• Epiretinal membrane. Membranes can form on the central retina to produces wrinkles (macular pucker). This blurs central vision and causes distortion (straight lines appear bent). It is possible to remove such membranes by vitrectomy.

• Advanced diabetic retinopathy (see pictures) Patients with severe diabetic eye disease may have vitreous haemorrhage and retinal detachment. In such cases vitrectomy may be required to remove blood from the vitreous, remove scar tissue and enable laser treatment.