Technology

Orbit – CT Scan

A computed tomography (CT) scan of the orbit is an imaging method. It uses x-rays to create detailed pictures of the eye sockets (orbits), eyes and surrounding bones. The use of advanced imaging to diagnose and treat eye-related problems in the emergency department has nearly doubled in the world in last few years, intensifying the need for evidence-based protocols to guide such ordering.

Why the Test is Performed

This test is helpful for diagnosing diseases that affect the following areas around the eyes:

• Blood vessels
• Eye muscles
• Nerves supplying the eyes (optic nerves)
• Sinuses

An orbit CT scan may also be used to detect:

• Abscess (infection) of the eye area
• Broken eye socket bone
• Foreign object in the eye socket

How the Test is Performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. Only your head is placed inside the CT scanner. You may be allowed to rest your head on a pillow.

Once you are inside the scanner, the machine’s x-ray beam rotates around you but you won’t see the x-ray. A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. The computer can create three-dimensional models of the body area by stacking the slices together.

You must lie still during the exam, because movement causes blurred images. You may be asked to hold your breath for short periods. The actual scan takes about 30 seconds. The entire process takes about 15 minutes.

Orbit – MRI

The Orbit MRI is similar to the brain MRI with additional images specific to the eyes. An MRI scan uses a magnetic field and pulses of radio wave energy to make pictures of your body. During an MRI to check for optic neuritis, you might receive an injection of a contrast solution to make the optic nerve and other parts of your brain more visible on the images.

It is important to determine whether there are damaged areas (lesions) in your brain. Such lesions indicate a high risk of developing multiple sclerosis. An MRI can also rule out other causes of visual loss, such as a tumor..

How the Test is Performed

In the scan room you will be asked to lie on your back onto an MRI coil (camera) and an additional coil will be clicked in place acting as an antenna. You will be provided with an eye mask to prevent motion of the eyes during this scan.

The length of a brain MRI is typically 20-25 minutes without a contrast injection. The total length of time is 30-35 minutes if a contrast injection is needed.

Orbit X-Ray

The orbit is the circle of thin bones that houses and protects the eye, even extending behind the eye and nearly wrapping around it. Orbital x rays are used to examine the surrounding structures containing the eye. It includes the surrounding structures protecting the eye, the eyebrow, the bridge of the nose and the cheekbone.

It is useful for:

• Detecting fractures of the surrounding bone (injury, trauma and disease),
• Detecting foreign objects in the eye – especially if you suspect metal in the eye prior to an MRI scan,
• Examining the sinuses.

Purpose

Orbital x ray, or orbital radiography, is often used to detect problems resulting from injury or trauma to the eye. The exam may also detect changes to the structure of the eye, which may indicate various diseases. An ophthalmologist may also order an orbital x ray if there is concern that foreign bodies may be present in the eye that cannot be detected with an instrument called an ophthalmoscope.

Preparation

There are no special dietary preparations needed prior to an orbital x ray. As with any radiography procedure, the patient should remove any jewelry or metal objects, which may interfere with a clear image.

Description

The orbital x ray involves several different views in order for the physician to clearly see various parts of the eye without obstruction. In orbital x rays, images of the unaffected eye may also be taken to compare its shapes and structures to those of the affected eye. Views may include side view (lateral), back to front (posteroanterior), base view, views from both sides, and an image from the center to one outside edge (half-axial projection). Projections of the optical canal will also be included. For all of these views, the patient may be seated upright or asked to lie on a table in the x ray room. The orbital x ray procedure should take about 15 minutes to complete.

Aftercare

No aftercare is required following this diagnostic test.