ODs can help diagnose systemic maladies through radiologic tests

Issue: December 2001

Optometrists are able to detect a variety of systemic diseases and anomalies based on ocular manifestations. In these cases, it is the optometrist’s responsibility to assess the situation and direct the patient toward the necessary medical care. One means of effectively making this determination is by ordering radiologic tests. While insurance matters may in some cases make referral more practical, many optometrists are quite adept at ordering and interpreting radiologic tests.

“You want to contour the test you are ordering to the disease you are looking for,” said Leonid Skorin Jr., OD, DO, FAAO, FAOCO, a practitioner in Albert Lea, Minn. “You need to consider where you are looking, what you suspect and which test would give you the best image for the particular disease you suspect.”

Several different ocular presentations may prompt an optometrist to order radiologic studies. Although these criteria vary among practitioners, there are certain “red flags” that are commonly recognized.

“I consider headache patients, patients who have unexplained vision loss, patients who present with optic nerve head swelling and trauma patients,” Dr. Skorin said. “I also would be concerned with fractures around the orbit or any patient I suspect of having sinusitis.”

MRIs and CT scans

Two of the most common radiologic tests ordered by optometrists are MRIs and CT scans, according to practitioners. “This provides an image of the brain and the brain stem. And in terms of the eye, you would look at the orbit and the chiasmal area,” said Judy Tong, OD, FAAO, a practitioner in Fullerton, Calif.

Dr. Tong said a CT scan is often helpful in assessing trauma to the globe. “If someone has a blatant trauma and a pure X-ray is not conclusive, many times, you would send him or her out for a CT [computed tomography] to look at the bony orbits,” she said. “You may follow that with an MRI [magnetic resonance imaging], but usually a CT scan with an X-ray is good for trauma.”

According to Jerome Sherman, OD, FAAO, a practitioner in New York, CT scans are preferable for detecting bone problems, while MRIs are more effective in dealing with soft tissue. “If we are concerned with bone abnormality, we’ll order a CT scan,” he said. “If we think it is in the brain, we’re probably better off with an MRI in most cases.”

Dr. Sherman said, in cases where there appears to be a problem with a blood vessel, he will order a magnetic resonance angiogram (MRA) in addition to an MRI. “An MRA is very helpful to discover problems with specific blood vessels,” he said. “It is typically ordered at the same time as an MRI.”

When a patient presents with a problem that appears related to the optic nerve and it is accompanied by visual acuity reduction or visual field abnormality, Dr. Sherman said he orders an MRI of the orbit as well as an MRI of the brain.

“In that case, the patient will be seen once for both tests, which are very similar,” he said. “The difference is, the MRI of the orbit will take a lot of slices through the orbit to make sure nothing is going on there.”

Dr. Skorin cited other presentations for which he would order a CT scan or an MRI. “For sinusitis, I usually request an unenhanced CT scan of the orbit,” he said. “If I suspect fungal sinusitis or tumor, then I would get an MRI scan. If I suspect a tumor in the orbit, I would order an MRI scan of the orbit, with or without gadolinium and with fat suppression.”

When looking for multiple sclerosis (MS), Dr. Skorin said he would order an MRI scan of the brain with or without gadolinium. “In that case, I would be looking for the periventricular white matter lesions,” he said.

If he sees a specific visual field deficit, such as a bitemporal hemianopia, Dr. Skorin said he would be looking for an abnormality in the area of the chiasm and would order an MRI scan with or without gadolinium.

He would also order an MRI for patients who present with papilledema, Dr. Skorin said. “If I see a patient with papilledema, and I want to rule out a brain tumor vs. pseudotumor cerebrae, I will order an MRI scan,” he said. “For pseudotumor cerebrae, you want to rule out any tumors, especially in the posterior fossa region.”

Other tests

Although CT scans and MRIs may be the most common radiologic studies, practitioners are able to glean valuable information from other types of X-rays, as well as blood tests.

“If we have a patient who is thought to perhaps have tuberculosis or sarcoid that is affecting the eye, we would order a chest X-ray,” Dr. Sherman said. “And some of the blood tests, in conjunction with the radiologic tests, can sometimes help us make the diagnosis.”

Dr. Sherman said recurring iritis and mutton fat keratoprecipitates suggest sarcoid, among other conditions. He said if the patient is black, this would further indicate sarcoid, because sarcoid is more common in black patients. In this case, Dr. Sherman suggested that the practitioner might order a blood test called an angiotensive converting enzyme (ACE) test.

“You might also order a chest X-ray,” he said, “because patients who might have sarcoid and have ocular findings will probably have an elevated ACE level and also something on their chest X-rays that suggests a granuloma in the lung.”

Patient profile, clinical findings

When ordering radiologic studies, it is important to consider the patient’s age, race, gender, history and medical information, as well as established findings on the disease in question. This will assist the practitioner in ordering the most appropriate test, said Dr. Sherman.

For example, a black woman presenting with recurring iritis would prompt a practitioner to look for sarcoid, Dr. Sherman said. However, in a young white man, these same symptoms would suggest a different anomaly — ankylosing spondylitis, a degenerative joint disease affecting the spine.

“The test to order for that would be an X-ray of the sacroiliac joint,” he said.

There is also a common set of ocular signs and symptoms that would indicate MS, Dr. Sherman said. “When I see female patients between the ages of 25 and 50 with sudden reduction of vision in one eye and pain on eye movements, and the eye itself looks OK, that will generally be optic neuritis,” Dr. Sherman said. “Patients who have what we call optic neuritis often end up with MS.”

Dr. Sherman said that between 70% and 75% of patients with optic neuritis develop MS within 10 years. “When somebody comes in with optic neuritis, we should get an MRI immediately,” Dr. Sherman said. “If the MRI shows what we call ‘paraventricular hot spots,’ that is highly suggestive of demyelinating disease.”

Cases for referral

In some situations, it is easier or more cost-effective for the optometrist to refer the patient out for radiologic testing. In many of these cases, insurance presents the main obstacle, according to practitioners.

“Even though the optometrist may have the knowledge to order the test, insurance might dictate that he or she refer it,” Dr. Tong said. “Or many times, insurance limits it until patients get an approval from their primary care physician. It varies from state to state.”

“There is no optometry law that would prevent optometrists from ordering radiologic testing,” said Sherry Cooper, state legislative analyst for the American Optometric Association. “It is possible, though, that there could be a restriction in the laws or regulations that govern the clinical laboratories.”

Ms. Cooper said some laboratory regulations may specify which classes of providers are permitted to order tests. “In that case, you would want to amend the law to be included on that list of accepted classes of providers,” she told Primary Care Optometry News. “But usually, it isn’t that specific.”

Ms. Cooper said in some states, the optometric legislation takes a proactive stance, specifying in the practice act that optometrists are permitted to order tests. “It is helpful in states where there may be some confusion,” she said.

In some instances, the optometrist may not feel comfortable interpreting the results of the test, Dr. Tong said. “I think most optometrists would feel more comfortable with ordering vs. interpreting,” she said. “I think a good portion of optometrists in the United States know how to interpret tests on an adequate level.”

Some practitioners rely primarily upon the radiologist for interpretation, but also assess the results themselves. “The radiologist reads them, but I read them, too,” Dr. Skorin said. “I might catch something he or she misses.”

Dr. Sherman, who orders radiologic tests about 25 times a year, said an optometrist’s confidence in ordering tests depends on his or her practice.

“If you have a general practice, and you see a relatively small number of patients, it will not come up that much,” he said. “If you are dealing with a large number of patients and a lot of referred patients, chances are you will order tests more often.”

For Your Information:

Leonid Skorin, OD, DO, FAAO, FAOCO, is a practitioner based in Albert Lea, Minn. He can be reached at Albert Lea Eye Clinic, Mayo Health Systems, 1206 W. Front St., Albert Lea, MN 56007; (507) 373-8214; fax: (507) 373-2819.

Judy Tong, OD, FAAO, can be reached at the Southern California College of Optometry, 2575 Yorba Linda Blvd., Fullerton, CA 92631; (714) 449-7429; fax: (714) 992-7811.

Jerome Sherman, OD, FAAO, is a Primary Care Optometry News editorial board member who practices in New York. He can be reached at SUNY College of Optometry, 33 West 42nd St., New York, NY 10306; (212) 780-5004; fax: (212) 780-4980.

Sherry Cooper is the state legislative analyst for the American Optometric Association. She can be reached at 243 N. Lindbergh Blvd., St. Louis, MO 63141; (800) 365-2219; fax: (314) 991-4101.