Enucleation is the surgical removal of the eyeball that leaves the eye muscles and remaining orbital contents intact.
Enucleation is performed to remove large-sized eye tumors or as a result of traumatic injury when the eye cannot be preserved. In the case of tumors, the amount of radiation required to destroy a tumor 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.
The two types of eye tumors 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 melano-cytes that house pigments. When the melanocytes become cancerous, the cancer is called a melanoma. If the tumor reaches the iris and begins to grow, or if there are symptoms, enucleation may be indicated.
- Retinoblastoma. Retinoblastoma is a malignant tumor 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 tumors 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 tumor, and radiation therapy to the other eye.
Data from the U.S. National Center for Health Statistics estimate that nearly 2.4 million eye injuries occur in the United States annually. This report calculated that nearly one million Americans have permanent significant visual impairment due to injury, with more than 75% of these individuals being blind in one eye. Eye injury is a leading cause of monocular blindness in the United States, and is second only to cataract as the most common cause of visual impairment. While no segment of the population escapes the risk of eye injury, the victims are more likely to be young. The majority of all eye injuries occur in persons under thirty years of age. Trauma is considered the most
common cause of enucleation in children over three years of age.
For the year 2000, Texas demographics for cancer of the eye and orbit were fewer than five per 100,000. According to the National Institutes of Health (NIH), there are about 2,200 cases of eye cancer diagnosed in the United States each year.
Following anesthesia, 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 postciliary vein. If a lesion has been found, the plane of section is modified so that the lesion is included in the slab.
Enucleation may be performed under general or local anesthesia. In either case, the injection is given in the retrobulbar space. An antibiotic and an anti-inflammatory medication such as dexamethasone are also given intravenously.
Because the eye is surrounded by bones, it is much easier for patients to tolerate enucleation than the loss of a lung or kidney. When surgery is performed under
Cornea— The transparent structure forming the anterior part of the fibrous tunic of the eye. It consists of five layers.
Glaucoma— A group of eye diseases characterized by an increase in intraocular pressure that causes changes in the optic disk and defects in the field of vision.
Intraocular melanoma— A rare form of cancer in which malignant cells are found in the part of the eye called the uvea.
Iris— The contractile eye membrane perforated by the pupil, and forming the colored portion of the eye.
Melanocytes— Color-containing cells in the uvea.
Melanoma— A malignant tumor arising from the melanocytic system of the skin and other organs.
Optic nerve— The nerve carrying impulses for the sense of sight.
Orbit— The cavity or socket of the skull in which the eye and its appendages are situated.
Retina— Thin nerve tissue that lines the back of the eye that senses light and forms images.
Retinoblastoma— Malignant (cancerous) tumor of the retina.
general anesthesia, patients do not feel or see anything until they regain consciousness. Additional local anesthesia is often given at the end of the surgery so that the patient will have the least pain possible when waking up in the recovery room. Most patients have a headache for 24–36 hours after surgery that is relieved with two regular headache medication pills, such as Tylenol, every four hours. A firm pressure dressing is maintained for four to six days; oral antibiotics are given for one week; and steroids, such as prednisone, adjusted according to patient status, are given three times daily for four days. The socket is evaluated after removal of the pressure dressing. If the edema has disappeared, the sutures are removed. Topical antibiotics are applied four times daily for four weeks.
Enucleation surgery is very safe. Only rarely do patients experience major complications, whicht may include bleeding, infection, scarring, persistent
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
Eye enucleation is usually performed by an ophthalmic surgeon or an ophthalmologist in a hospital setting. Young and healthy patients may undergo the surgery on an outpatient basis but most stay in the hospital for at least one night after surgery. Ophthalmic surgeons are members of the American College of Eye Surgeons, and are certified by the American Board of Eye Surgery after submitting to an extensive written application. Before ABES certification, they must be certified by the American Board of Ophthalmology (ABO). This certification indicates successful completion of an approved residency program and acquisition of sufficient knowledge in the areas of medical and surgical ophthalmology.
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.
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.
In a study performed by the National Eye Institute on melanoma patients at five-year follow-up, 82% of the patients who underwent enucleation remained alive. At a 10-year follow-up, 31% remained alive. As of 2003, the study was ongoing and would follow all patients for up to 15 years.
There are no alternatives to enucleation because it is a procedure of last resort performed when other treatments have failed.
QUESTIONS TO ASK THE DOCTOR
- Why is enucleation required?
- Will there be pain after surgery?
- How many enucleation surgeries do you perform in a year?
- How much time will I need to recover from the operation?
- When can I get a prosthesis?
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American Academy of Ophthalmology. P.O. Box 7424, San Francisco, CA 94120-7424. (415) 561-8500. http://www.aao.org/index.html.
American College of Eye Surgeons. 2665 Oak Ridge Court, Suite A, Fort Myers, FL 33901. (239) 275-8881. http://www.aces-abes.org/.
National Cancer Institute. Suite 3036A, 6116 Executive Boulevard, MSC8322, Bethesda, MD 20892-8322.(800)422-6237. <http://cancer.gov/>.
Finger, Paul T., MD, FACS. “Enucleation.” Eye Cancer Network. [cited May 5, 2003]. http://www.eyecancer.-¥com/Enucleation/enuc.html.
Monique Laberge, Ph.D.
Enzyme immmunoassay seeImmunoassay tests