There are two situations where a lens may be dislocated into the back of the eye.
During cataract surgery, the patient’s own lens may move into the back portion of the eye and become mixed in with the vitreous gel that fills with the eye. If this happens during cataract surgery, the cataract surgeon cannot retrieve the lens or fragments of the lens as special instruments and techniques are required. The patient is usually seen on an urgent basis by the retina doctor and plans are made to remove the lens fragments in the vitreous with vitrectomy surgery, usually within a few days. An artifical intraocular lens (IOL) can be placed in the eye at a later date, after the eye has healed from the vitrectomy surgery.
The second situation is when an artificial intraocular lens (IOL) that has been placed inside the eye with previous cataract surgery tumbles into the back of the eye and becomes mixed in the vitreous gel. In some cases, the lens can be retrieved from the back of the eye using vitrectomy surgery and re-suspended in the front of the eye. In other cases the lens is retrieved from the back of the eye with vitrectomy surgery, removed completely from the eye, and then a new lens is put into the eye. Usually this second new lens is placed in the “anterior chamber” to avoid the lens falling into the back of the eye in the future.