X Rays of the Orbit
X Rays of the Orbit
Orbital x rays are a radiographic study of the area and structures containing the eyes. The orbits are bony cone-shaped cavities that contain and protect the eyes. Each orbit is lined with fatty tissue to cushion the eyeballs. The orbits are thin and easily subjected to fractures, particularly blow-out fractures of the orbital floor.
Orbital x ray, or orbital radiography, is used to detect problems resulting from injury or trauma to the eye. Seventy percent of all facial fractures involve the orbits in some way. An x ray of the orbits may also be ordered for patients complaining of pain, vision trouble, or excessive tearing of the eyes. An ophthalmologist may also order orbital x rays when a foreign body cannot be detected with an ophthalmoscope.
Orbital x ray is also used as a screening tool before an MRI is performed, since intraorbital metallic foreign bodies are a contraindication for MRI (the magnetic field in the MRI could move the metallic object causing eye injury). Patients scheduled for MRIs are screened for the possible presence of metallic foreign bodies by a questionnaire or interview with the MRI technologist. If there is a suspicion that a metallic foreign body may be present, the patient will have x rays taken of the orbit to ensure that no foreign body is present.
Pregnant women and women who could possibly be pregnant should only receive orbital x rays when absolutely necessary. The x-ray technologist will use protective shielding on all women of child-bearing age as well as on children.
Each orbit is formed by the frontal, ethmoid, and sphenoid bones of the skull and the lacrimal, palantine, maxillary, and zygomatic bones of the face. Each orbit consists of a medial and lateral wall as well as a roof and floor, therefore a series of views is necessary to see all of the structures well. Both orbits are always imaged so that a comparison can be made of the two sides. A typical routine for the orbits consists of a Water's view, Caldwell and lateral of the affected side. In some cases a basal view may be requested if the patient is able to extend the head backwards. Projections of the optic canals or Rhese views will be included in some cases.
X rays of the orbits may be done with the patient sitting or lying down. The patient is placed prone (lying horizontally face down) with no rotation of the head. The tube is angled 15 caudad (towards the feet) for the Caldwell position, where the petrous ridges will be in the lower third of the orbits. In the Water's position (occipito-mental) the chin is extended forward at least 37°, centering on the acanthion (the small indentation in the center of the upper lip). This is the best view to see the orbits completely clear of any other structures. The maxillary sinuses are well visualized with the Water's view, so any fluid levels are easily detected. In the lateral position the patient's head is turned onto the affected side if possible, with the interpupillary line perpendicular to the table.
When x rays for a foreign body are requested, a Water's view is done with the patient looking straight ahead. Sometimes two views in the lateral position are done—one with the patient looking up and one with the patient looking down. A soft tissue technique should be used when looking for a foreign body. An ultrasound exam of the eye also will detect any foreign body in the eye.
X rays of the orbits should normally be completed in 15 minutes if the patient is cooperative. The patient must wait until the x rays are developed to ensure that all required structures are well demonstrated with no rotation or movement.
There are no special dietary preparations needed prior to an orbital x ray. As with any radiography procedure, the patient should remove dentures, jewelry, or metal objects, which may interfere with obtaining a detailed image.
No aftercare is required following this diagnostic test.
Radiation exposure is low for this procedure and all certified radiology facilities follow strict personnel and equipment guidelines for radiation protection. Women of child-bearing age and children will be given a protective shielding (lead apron) to cover the genital and/or abdominal areas. Patients who are unable to lie prone can be tested in a supine position (lying horizontally on the back). The lateral view can be done by turning the x-ray tube 90° and placing the film against the affected side. Severe trauma patients will have a CT scan done instead of orbital or facial x rays.
Normal findings show the bones of the orbits are intact, with no fractures, tumors, or cysts that could erode the surrounding bone.
Positive findings from an orbital x ray may show that there has been some injury to the eye. Radiologists look for asymmetry in the facial bones, periorbital or intracranial air as well as fluid in the paranasal sinuses. Tiny fractures in the orbital bones can usually be detected on the radiograph. In a blowout fracture (one involving the orbital floor), radiographic findings may include overlapping of bone fragments on the orbital floor and opacification of the sinuses (due to hemorrhage).
Indications of differences in size and shape of the various structures in the orbit may be apparent. The orbit may be enlarged, indicating irritation from an injury or foreign body. A number of growing tumors within the eye or brain area may also cause orbital enlargement. Destruction of the walls of the orbit may indicate a nearby infection or malignancy. Changes in density may also be a sign of bone disease or a cancer that has spread to the bone.
Children's orbits are more likely to be enlarged by a fast growing lesion, since their orbital bones have not fully developed, but are less likely to have facial fractures due to the resiliency of their facial skeleton.
Health care team roles
The x-ray technologist works as part of the treatment team to make sure that the patients are radiographed and then returned to the emergency department as soon as possible. If portable (mobile radiography) orbital x rays are ordered the radiography technologist must make sure that all staff members remaining in the room wear proper shielding (lead aprons).
Patients are instructed to remain still during the x rays and to allow the x-ray technologist to position the head. Certain positions may be uncomfortable but are necessary to visualize all areas of the orbits. All radiologic technologists must be certified and registered with the American Society of Radiologic Technologists.
Blowout fracture— A fracture or break in the orbit that is caused by a sudden and violent impact to the area.
Malignancy— A tumor that is cancerous and growing.
Medial wall— The mid-line bone, or wall, of the eye's orbit. It is generally thicker than the roof and floor walls.
Ophthalmologist— A physician who specializes in the workings, structures, and care of the eyes.
Ophthalmoscope— An instrument routinely used by ophthalmologists to examine the interior of the eye. It consists of a small light, a mirror, and lenses of differing powers that magnify.
Periorbital— The area surrounding the eye.
Radiography— Examination of any part of the body through the use of x rays. The process produces an image of shadows and contrasts on film.
Water's view— A radiographic view of the facial bones invented by Dr. S. Water to see all of the facial bones clearly. The patient is prone with the head straight and the chin extended forward 37°.
Ballinger, Frank, et al. Merrill's Atlas of Radiographic Positioning. 9th ed. St. Louis, MO: Mosby Yearbook, 1999.
Schull, Patricia, ed. Illustrated Guide to Diagnostic Tests. 2nd ed. Springhouse PA: Springhouse Corporation, 1998.
American Academy of Ophthalmology. P.O. Box 7424, San Francisco, CA 94120-7424. (415) 561-8500.
National Eye Institute. Building 31, Room 6A32, Bethesda, MD 20892. (301) 496-5248. 〈http://www.nei.nih.gov〉.
Eye Institute. University of Pennsylvania Health System. 〈http://www.med.upenn.edu/ophth/patinfo〉.