Today’s glaucoma diagnosis techniques combine IOP, visual field, retinal imaging

Issue: February 1999

When it comes to initiating glaucoma treatment, the process can be separated into three parts: screening, full examination and deciding on a course of treatment. Although making the decision to screen can be subjective, the clinicians Primary Care Optometry News interviewed for this article agreed that family history, age and race play significant roles in that decision.

“The first thing to consider would be family history. If there’s a family history of glaucoma, that patient’s automatically more suspicious. With black patients, generally, there’s a higher incidence of glaucoma,” noted Stuart Rothman, OD, in private practice in Livingston, N.J.

Tonometry: part of routine exam

Whether Goldmann or the “air-puff” method, tonometry has its rightful place as an integral part of a basic work-up. “Typically, we do tonometry during any routine examination,” Dr. Rothman said.

Dr. Lalle agrees that tonometry is essential no matter who performs the test. “Whether the technician does it or the doctor does it is immaterial,” he said. “It’s part of the exam.”

Although he employs the Goldmann tonometer “almost exclusively,” Dr. Sherman says that the air-puff method still has its place in an exam. “I use it on occasion,” he said. “It’s accurate enough; I don’t really see a problem with it. But if there’s any question at all, we’d rather go with Goldmann.”

Not all patients — such as those with high levels of corneal rigidity — are good candidates for the Goldmann method, however. In some cases, “the results on a noncontact tonometer may be just as reliable as what you’d expect to get on Goldmann,” said Dr. Rothman. “The advantage of Goldmann is that you’re actually touching the cornea, so you get some sense of resistance and a better idea of what you’re dealing with.”

Dr. Lalle added that checking for elevated intraocular pressure (IOP) and checking the optic nerve and nerve fiber layer are also included while examining the patient. During the exam, certain indicators may crop up to raise an eyebrow and spur the doctor to pursue further testing. “You assess the optic nerve and the nerve fiber layer and decide whether or not there’s a suspicion for glaucoma,” Dr. Lalle said. “If there is a suspicion, I measure the optic nerve head and I will take stereo photos of the optic nerve. I try to assess the nerve fiber layer a little bit better and I start considering formal field tests, such as blue on yellow or white on white.”

Further testing

Dr. Rothman suggested a similar course of action based on the findings. “At the follow-up evaluation, we would re-check the IOP and do a visual field evaluation and gonioscopy,” he said. “If we hadn’t already done a dilated examination, we would do that, with a fundus contact lens to get a stereoscopic view of the optic nerve head.”

Peter Lalle, OD, of the Eye Clinic at the Baltimore Veterans Administration Medical Center, said that Frequency Doubling Technology, or FDT (Welch Allyn, Skaneateles Falls, N.Y.), in visual field tests can zero in on potential problems of at-risk patients. “The nicest thing about the FDT visual field instrument (Humphrey Systems, Dublin, Calif.) is that you can adjust the sensitivity of the test,” said Dr. Lalle.

“For high-risk patients, you can dial the sensitivity up a little bit and be more stringent in your criteria,” he added. When using the FDT in the screening mode, the procedure takes only about 45 seconds an eye and lacks a complicated set-up process, Dr. Lalle said.

Jerome Sherman, OD, professor at the SUNY State College of Optometry, is an advocate of the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies, San Diego, Calif.) for screening patients. The GDx uses polarized light to measure nerve fiber layer thickness and assess glaucomatous damage.

“In the real world, most people don’t have access to the high-tech GDx, and they may want to do visual fields on everybody,” he said. “That’s probably a good idea. The GDx can be used as a screening test for a relatively large number of patients because it can generate a lot of information on a lot of people very quickly. The major drawback is that it’s expensive; however, you don’t have to touch the cornea or dilate the pupil,” he said.

“I’ll go to the GDx because, in my experience, it allows me to pick up a lot of the defects or a lot of the abnormalities of the nerve fiber layer that have been missed on the rest of the examination,” he said. “Also, we take a careful history, measure pressure, look at the discs very carefully through a dilated pupil and do some form of visual field screening on many patients.”

Other newer forms of visual field testing in addition to the FDT include tendency-oriented perimetry (TOP), Swedish interactive threshold algorithms (SITA) and short-wavelength automated perimetry (SWAP), all of which are more extensive visual field tests if a potential problem is detected. “SWAP is not very helpful as a routine procedure, because many patients seem to fail it the first time they do it even though they don’t have a problem,” Dr. Sherman said. “You have to repeat it several times before you start getting consistent results, so it’s a difficult test for patients to take.”

Dr. Rothman uses the Synemed (Benicia, Calif.) static perimeter. “It has a computerized software analysis program that allows for comparison of data over time,” he explained. “The fast threshold program allows a central 30º field to be completed in as little as 2½ minutes per eye.”

When to begin treatment

Sometimes, a combination of many factors will determine how quickly treatment should begin, if at all, the doctors said. While elevated IOP may give a practitioner pause, it is only in combination with other factors that ocular hypertension requires immediate intervention. “Somebody who has a borderline high IOP may not get treated if the optic nerve looks normal and if the visual field looks normal,” Dr. Rothman said. “Someone who has borderline high pressures with normal-looking optic nerves and visual fields that may be somewhat suspicious may not be treated immediately, either, but certainly the visual fields would be repeated to see if there was consistency. At that point, if there was consistency, there might be treatment.”

Dr. Lalle agreed that the decision to treat can be quite subjective. “If I see marked damage to a patient’s optic nerve and very high IOP, I would probably consider starting treatment that day or, if nothing else, bring him or her in the next day for a second IOP reading and maybe a third reading the very next day. Usually, you like to get three readings before you start treatment,” he said.

Once a patient is considered a glaucoma suspect, the follow-up schedule varies from person to person depending on the findings. “If they’re strong glaucoma suspects, I may have them back in 3 months,” Dr. Sherman stated. “If they’re not a suspect at all, it may be a year or two.”

Dr. Lalle said that the results of the FDT are a good indicator of how aggressive the treatment should be. “For markedly high pressures and obvious damage, do a quick work-up as soon as possible,” he stressed. “But for ambiguous cases, you can stretch it over 6 months to a year.”

Future diagnostic tools

In the future, instruments such as the Zeimer self-tonometer (CDS Technologies, Wheaton, Ill.) may help make testing for glaucoma easier and more convenient than ever. With this relatively new instrument, patients can check their own IOP at home throughout the day.

Dr. Lalle said that while he is somewhat familiar with the new tool, he would be reluctant to use or recommend it just yet. “You need a little bit more information as to how you would use that data,” he noted. “If you found out that someone was spiking at odd times, how would you modify their treatment? Is there any proven medicine or surgical treatment that will dampen those spikes? Without a prospective study showing how you could actually change the course of the disease with this knowledge, it’s speculation.”

Dr. Sherman expressed an interest in the Fresco Phosphene Tonometer (FPT), presented by Bernard B. Fresco, OD, MS, of Toronto at the American Academy of Optometry meeting in San Francisco.

“It looks very interesting,” Dr. Sherman said. “It actually measures pressure, but, in addition to that, if the patient has a field loss in certain areas, it will pick that up, too. So it is a combination tonometer-field tester, in a strange way.”

No matter what type of testing is used, glaucoma is a condition that should not be taken lightly and should ideally be screened in all patients, noted Dr. Sherman. “We look at glaucoma as being the single most common cause of preventable blindness,” he said. “This means that every clinician, on every visit, should be concerned about glaucoma.”

For Your Information:

Stuart Rothman, OD, may be reached at 349 E. Northfield Rd., Ste. LL3, Livingston, NJ 07038; (973) 992-0998; fax: (973) 992-8961. Dr. Rothman has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Peter Lalle, OD, can be reached at the Baltimore VA Medical Center, 10 North Greene St., Baltimore, MD 21201; (410) 605-7230; fax: (410) 605-7232. Dr. Lalle has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Jerome Sherman, OD, can be reached at SUNY, 100 E. 24^th St., New York, NY 10010; (212) 780-5004; fax: (212) 780-5207. Dr. Sherman has no direct financial interest in any products mentioned in this article, nor is he a paid consultant for any companies mentioned.

The Frequency Doubling Technology visual field instrument is available from Humphrey Systems, (877) HUMPHREY; e-mail: info@humphrey.com.

The GDx Nerve Fiber Analyzer is available from Laser Diagnostic Technologies, 9550 Waples St., Ste. 105, San Diego; CA 92121; (619) 558-9144; fax: (619) 558-9145.

The Synemed static perimeter is available from Synemed, 4562 E. Second St., Benicia, CA 94510; (800) 777-0650; fax: (707) 745-6409; e-mail: synemed1@aol.com; web site: www.synemed.com.

The Zeimer Self-Tonometer is available from CDS Technologies, 2043 Spring Green Drive, Wheaton, Il 60187; (630) 231-9665; fax: (630) 682-5687.

For information on the Fresco Phosphene Tonometer, contact Bernard B. Fresco, OD, MS, at 40 Saint Clair Ave. East #303, Toronto, ON M4T 1M9, Canada; e-mail: fppt@aol.com.