X Rays of the Orbit Health Article

Definition

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.

Purpose

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.

Precautions

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.

Description

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 sit ting 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.

Preparation

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.

Aftercare

No aftercare is required following this diagnostic test.

Complications

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.