Yes, it looks like there are reasons not to do a CT scan in this case. CT
(computed tomography) scanning uses x-rays, and sometimes causes severe side
effects, especially in children. MRI (magnetic resonance imaging) is a safer,
but more expensive procedure. CT scans are most effective during the 48-72
hours after a trauma. MRI scans are more effective later (during the post-acute
The section on Black Eye from the National Center of Emergency Medicine
Informatics does not recommend getting x-rays if there are "no palpable
"The patient has received blunt trauma to the eye, most often from a fist, a
fall, or a car accident, and is alarmed because of the swelling and
discoloration. Family or friends may be more concerned than the patient about
the appearance of the eye. There may be an associated subconjunctival
hemorrhage, but the remainder of the eye exam should be negative and there
should be no palpable bony deformities, diplopia or subcutaneous emphysema.
What not to do:
Do not get unnecessary radiographs. Minor injuries with normal eye exams and no
palpable deformities do not require x rays.
Do not brush off bilateral deep periorbital ecchymoses ("raccoon eyes")
especially if caused by head trauma remote to the eye. This may be the only
sign of a basilar skull fracture.
Black eyes are most commonly nothing more than uncomplicated facial contusions.
Patients become upset about them because they are so "near the eye," because
they produce such noticeable facial disfigurement, and because there is often
secondary gain being sought against the person who hit them. Nonetheless,
serious injury must always be considered and ruled out prior to the patient's
discharge from your care."
If you search MedLine (http://www4.ncbi.nlm.nih.gov/entrez/query.fcgi), e.g.,
tomography [mh] AND eye [mh] AND injury AND human [mh]
tomography [mh] AND eye [mh] AND "radiation protection" [mh] AND human [mh]
you will find some articles that emphasize the risks of CT scanning for
AJNR Am J Neuroradiol 2001 Jun-Jul;22(6):1194-8
Radioprotection to the eye during CT scanning.
Hopper KD, Neuman JD, King SH, Kunselman AR.
Department of Radiology, Penn State University, Hershey, PA 17033, USA.
"BACKGROUND AND PURPOSE: The lens of the eye is sensitive to radiation.
Children undergoing CT of the head and patients undergoing repeated CT scanning
of the head are vulnerable to this complication."
Irradiation dose to the lens of the eye during CT of the head.
Lund E, Halaburt H.
"The irradiation dose to the lens of the eye during CT scanning has been
measured in 16 patients. The dose is greatly influenced by changes in gantry
angulation, the position of the patient, the thickness and number of
slices, KV, and milliamperage. The total lens dose has been measured to be
higher than previously reported.
Repeated CT scans imply the risk of irradiation cataract, especially in infants
If you go to an ophthalmologist, read up on different diagnostic techniques.
MRI and CT scanning are two most popular imaging techniques used for examining
soft tissues of the head. CT scan uses x-rays, and MRI uses radio waves and a
strong magnetic field to obtain images of the head. MRI has fewer side
effects. MRI is more expensive than CT scanning, and CT scanning is more
expensive than regular x-rays.
You will find some detailed and authoritative information about different
diagnostic techniques on the National Library of Medicine website; they provide
a section on Diagnostic Imaging on their Medline Plus site:
There are links on that page to some information about MRI and CT scans of the
head on the Radiological Society of North America website, outlining risks vs.
benefits of each procedure:
CT scan of the head
"What is CT Scanning of the Head?
CT (computed tomography), sometimes called CAT scan, uses special x-ray
equipment to obtain many images from different angles, and then join them
together to show a cross-section of body tissues and organs. CT scanning
provides more detailed information on head injuries, brain tumors, and other
brain diseases than do regular radiographs (plain films). It also can show
bone, soft tissues, and blood vessels in the same images. CT of the
head and brain is a patient-friendly exam that involves little radiation
What are the benefits vs. risks?
CT of the head is now widely available and is performed in a relatively short
time and at a reasonable cost - especially when compared to MR imaging.
The exam shows changes in bone better than any other imaging method.
It is the only method that provides detailed images of bone, soft tissue, and
CT is becoming the method of choice for rapidly screening trauma victims to
detect internal bleeding or other life- threatening conditions.
CT does involve exposure to radiation in the form of x-rays, but the benefit
of an accurate diagnosis far outweighs the risk. The typical radiation dose
from a CT exam of the head and brain is equivalent to the amount of natural
background radiation received over a year's time. Among all radiological
procedures, radiation exposure from CT of the head is intermediate.
Special care is taken during x-ray examinations to ensure maximum safety for
the patient by shielding the abdomen and pelvis with a lead apron, with the
exception of those examinations in which the abdomen and pelvis are being
imaged. Women should always inform their doctor or x-ray technologist if there
is any possibility that they are pregnant.
Nursing mothers should wait for 24 hours after contrast injection before
resuming breast feeding.
The risk of serious allergic reaction to iodine-containing contrast material is
rare, and CT units are well equipped to deal with them.
What are the limitations of CT Scanning of the Head?
Compared to MR imaging, the precise details of soft tissue (including some deep
parts of the brain) are less visible on CT scans. CT is not sensitive in
detecting inflammation of the meninges -- the membranes covering the
MRI of the head
"What is MR Imaging (MRI) of the Head?
MRI (magnetic resonance imaging) uses radio waves and a strong magnetic field
rather than x-rays to provide remarkably clear and detailed pictures of
internal organs and tissues. This technique has proved very helpful to
radiologists in diagnosing tumors of the brain as well as disorders of the eyes
and the inner ear. It requires specialized equipment and expertise and allows
evaluation of some body structures that may not be as visible with
other imaging methods.
What are the benefits vs. risks?
Images of the brain and other head structures are clearer and more detailed
than with other imaging methods.
MRI contrast material is less likely to produce an allergic reaction than the
iodine-based materials used for conventional x-rays and CT scanning.
Exposure to radiation is avoided.
MRI enables the detection of abnormalities that might be obscured by bone
tissue with other imaging methods.
A variant called MRI angiography provides detailed images of blood vessels in
the brain without the need to inject contrast material.
New MRI systems can depict brain function, and in this way detect a stroke at
a very early stage.
An undetected metal implant may be affected by the strong magnetic field.
MRI is generally avoided in the first 12 weeks of pregnancy. Doctors usually
use other methods of imaging, such as ultrasound, on pregnant women, unless
there is a strong medical reason.
What are the limitations of MRI of the Head?
Bone is better imaged by conventional x-rays, and CT is preferred for patients
with severe bleeding. MRI may not always distinguish between tumor tissue and
edema fluid, and does not detect calcium when this is present within a tumor.
In most cases the exam is safe for patients with metal implants, with the
exception of a few types of implants, so patients should inform the technician
of an implant prior to the test. The exam must be used cautiously in early
pregnancy. MRI often costs more than CT scanning."
There's a discussion of different imaging methods on the Listen Up site, which
includes a review of MRI risks.
"Question: Is MRI dangerous?
Answer: Not usually.....There are some people that should not have an MRI.
Top of the list are folks that have cochlear implants or pacemakers. People
with metal fragments in their eyes or aneurysm clips implanted in their
brain should also avoid MRI examinations. The strong magnetic fields can
dislodge metal objects that are in the body. Even worse they can overload
implanted electronic devices and render them useless. Always tell your
physician and the technologist if you have implanted medical devices before you
enter the magnet suite.
How soon does it make sense to do a CT or MRI scan?
"The initial CT scan appearance often underestimates the actual brain injury
and the patients clinical condition may be much worse than the CT scan would
suggest. Diffuse injury evloves and becomes more prominent on CT during
the next 48-72 hours after injury."
Center for Neuro Skills' Traumatic Brain Injury Resource Guide
"CT (computerized tomography): In the emergency department, CT is primarily
used to evaluate acute TBI. CT scans detect acute hematomas and other areas of
MRI (magnetic resonance image): This tool provides greater definition of
lesions than the CT scan. Cellular density as well as water diffusion and blood
perfusion is assessed. MRI is the best tool to evaluate neurological changes in
the post-acute phase of recovery."
Also try these Google searches:
eye OR ophthalmic ct OR imaging
eye OR ophthalmic injury OR trauma diagnosis OR diagnostic