Enucleation of the eye

Enucleation is the surgical removal of the eyeball that leaves the eye muscles and remaining orbital contents intact.

Removal of an eye is considered a drastic and traumatic measure to most people.  Although many patients who require this surgery have no vision in the affected eye, those who do have vision recognize that enucleation will result in instantaneous, permanent, total blindness of that eye.  Furthermore, all patients who undergo this procedure will require an artificial eye (ocular prosthesis) as a cosmetic substitute for the real eye. 

Purpose

Enucleation is performed to remove large-sized eye tumours or as a result of traumatic injury when the eye cannot be preserved. In the case of tumours, the amount of radiation required to destroy a tumour of the eye may be too intense for the eye to bear. Within months to years, many patients who are treated with radiation for large ocular melanomas lose vision, develop glaucoma, and eventually have to undergo enucleation.

Enucleation is usually performed for several different reason:

• to remove a malignant tumour that has developed within the eye
• to alleviate intolerable pain in a blind eye affected by a condition such as uncontrollable glaucoma
• to reduce the risk of “sympathetic ophthalmic” 
• severe inflammation of unknown cause which may affect the remaining eye when one eye has been severely injured and blinded.

The two types of eye tumours that may require enucleation are:

• Intraocular eye melanoma. This is a rare form of cancer in which malignant cells are found in the part of the eye called the uvea, which contains cells called melanocytes that house pigments. When the melanocytes become cancerous, the cancer is called a melanoma. If the tumour reaches the iris and begins to grow, or if there are symptoms, enucleation may be indicated.
• Retinoblastoma. Retinoblastoma is a malignant tumour of the retina. The retina is the thin layer of tissue that lines the back of the eye; it senses light and forms images. If the cancer occurs in one eye, treatment may consist of enucleation for large tumours when there is no expectation that useful vision can be preserved. If there is cancer in both eyes, treatment may involve enucleation of the eye with the larger tumour, and radiation therapy for the other eye.

The Surgery

Diagnosis/Preparation

Enucleation may be performed under general or local anaesthesia. Enucleation is usually performed under general anaesthesia, although it can be done under local anaesthesia by numbing the entire eye and socket tissues prior to the surgery.  The procedure generally takes no more than 60 – 90 minutes. An antibiotic and an anti-inflammatory medication such as dexamethasone are also given intravenously.

Surgical Procedure

Following anaesthesia, the surgeon measures the dimensions of the eye globe, length of the optic nerve, and horizontal dimensions of the cornea. The surgeon then illuminates the globe of the eye before opening it. A dissecting microscope is used to detect major features and possible minute lesions. The eye is opened with a sharp razor blade by holding the globe with the left hand, cornea down against the cutting block, and holding the blade between the thumb and middle finger of the right hand. Enucleation proceeds with a sawing motion from back to front. The plane of section begins adjacent to the optic nerve and ends at the periphery of the cornea. The plane of section is dependent on whether a lesion has been detected. If not, the globe is cut along a horizontal plane, using as surface landmarks the superior and inferior oblique insertions and the long post ciliary vein. If a lesion has been found, the plane of section is modified so that the lesion is included in the slab.

Immediately after the eyeball has been removed, an orbital implant, only slightly smaller than the eye, is inserted deep in the socket.   The eye muscles are attached to the implant to improve motility.  The implant is covered externally with the pink surface tissue that lines the eyelids and the ultimate result is a surface that is similar to the inner lining of the mouth.

Postoperative Care

At the completion of the enucleation, a pressure patch is applied over the eyelids.  This patch is intended to keep swelling of the socket tissues to a minimum.  It is generally kept in place for about one to four days after surgery.  During the time this patch is in place, the patient commonly experiences some difficulty opening the lids of the unoperated eye. This can be quite frightening to the patient.

Fortunately, the difficulty in opening the eyelids generally resolves itself after the first post-operative day.  Moderate post-surgical pain in the socket generally occurs during the first 24 hours, but pain relievers are usually prescribed as needed to reduce this discomfort.  After the pressure patch is removed, the eyelids are usually swollen and black-and blue for a few days.  The use of ice compresses on the eyelids generally helps to reduce the swelling rapidly.  Ointment which promotes healing of the socket tissues are usually started as soon as the pressure patch has been removed. 

Risks

Enucleation surgery is very safe; only rarely do patients experience major complications. Complications include the following: bleeding, infection, scarring, persistent swelling, pain, wound separation, and the need for additional surgery. Complications may also occur with the orbital implants routinely used with patients who have undergone enucleation. Among these is the risk of infection.

Normal results

Within two to six weeks of enucleation surgery, patients are sent for a temporary ocular prosthesis (plastic eye). Besides the swelling and the black eye, patient features look normal. After a final prosthetic fitting, 90% of patients are usually quite happy with the way they look; 80% say others cannot even tell that they have only one eye.

Alternatives

There are no alternatives to enucleation because it is a procedure of last resort performed when other treatments have failed.

Integrated Implants

Some of the older implants, such as plastic or silastic, have a natural appearance when the patient looks straight ahead, but do not move like the opposite eye, since they are not integrated.  However, newer types of orbital implants allow movement of the artificial eye.  These prostheses are called integrated orbital implants, such as Medpore or hydroxyapatite (Bio-Eye).  These implants are inserted into the patient’s orbit immediately following enucleation.  The muscles that move the eye are the sutured around the implant.  The muscles move the implant up and down, which transmits the motion to the artificial eye (ocular prosthesis).

Occasionally, patients would like more motility, or movement of the artificial eye.  In about six months, when blood vessels have grown into and around the implant, a small hole may be drilled into the implant, so that a peg can be inserted under local anaesthesia.  (This is done rarely).  The prosthesis is attached to the peg like a ball and socket joint.  It transmits the movement of the implant to the overlying prosthesis, so that it moves along with the patient’s other eye.  The peg also helps to support the weight of the prosthesis, which may prevent the lower eyelid from sagging.  Not all patients are candidates for this type of implant, and research has shown that up to half of the patients that receive a peg have problems with the peg system.  Most patients have excellent motility without the peg procedure.  Dr. Singh will evaluate what is best for you. 

Ocular Prostheses

The cosmetic artificial eye (ocular prosthesis) is a plastic device that is moulded to fit between the eyelids over the conjunctiva that covers the ball implant.  This prosthesis is generally made three to six weeks after enucleation, in order to allow the socket tissues time to heal adequately.  Prior to that time, a thin clear plastic plate (conformer) is usually worn in place of the prosthesis.  This conformer helps to prevent shrinkage of the space between the inner surface of the lids and the mucus membrane covering of the ball implant.  Until the ocular prosthesis is fitted, the upper eyelid may be droopy.  The eyelid droop usually resolved in several weeks or months, but may occasionally require surgery to lift the eyelid.  In some cases, the ocular prosthesis supports the eyelid and generally allows the lids to open and close normally.

Some tearing of the eye is normal once the prosthesis is in place.  In some patients, thick mucus may build up on the prosthesis requiring that the artificial eye be removed and washed off from time to time.  In most instances, mucous build-up can be washed off the prosthesis and out of the socket by using an irrigation solution without removing the prosthesis.  However, most patients remove their prosthesis for cleaning once every one to three months.