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As perimetry options improve, visual field testing grows in importance beyond glaucoma
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Perimetry, both screening and full threshold visual fields, continues to play an important role for the primary care optometrist in detecting, diagnosing and managing a variety of eye conditions in addition to glaucoma.
The decision to add perimetry to a practice is best made after considering how many patients would benefit from it, according to practitioners interviewed by Primary Care Optometry News. These clinicians also find perimetry valuable as a screening tool that augments a clinical exam and as an essential management tool for glaucoma patients.
Practitioners who use perimetry routinely in their practices also hope today's advances in perimetry, which deliver faster, more accurate tests, will one day lead to objective perimetry testing for better patient care.
Screening, evaluation
Elliott M. Kirstein, OD, in general group practice in Cincinnati, finds perimetry invaluable for primary care patients and essential in managing glaucoma patients. "We use our perimeter all day long for screening on routine exams and for evaluating specific pathologies such as age-related macular degeneration, stroke, tumors, optic neuritis and neuropathies," he said.
Jerome Sherman, OD, Distinguished Teaching Professor at the State University of New York, recommends routine visual field screenings. "I am not at the point yet where I screen everyone, but we try to screen as many patients as we can," he said. "By doing screenings, which are rapid to administer and give us information we can use, we can detect conditions of the retina, optic nerve and visual pathway that were not suspected."
Dr. Sherman screens all patients who are glaucoma-suspect and any patient who experiences reduced vision with no obvious cause. "Many people have been diagnosed with amblyopia, for example, and it turns out to be a brain tumor," he said. "A screening visual field would have at least detected something wrong along the visual pathway."
Protocol indicates recommending test
In his multi-doctor office in West Chester, Pa., Richard Clompus, OD, estimates that doctors in his practice perform five to eight visual field tests per day. "We are able to identify areas with visual fields that need to be closely watched that we would not have picked up clinically," he said.
Dr. Clompus used to use a protocol to help him decide when a patient needed a full threshold visual field test. "We felt we could either find something with a positive family history, elevated IOP or optic nerve change," he said, "so there is some indication of when we should recommend a visual field."
Since installing the Humphrey/Welch Allyn Frequency Doubling Technology (FDT) 3 months ago, Dr. Clompus offers screening visual fields to more patients more often. Specifically, he offers a screening visual field test to patients older than 40 for a $15 fee. The procedure has been readily accepted by many patients.
"We have the FDT instrument on a rotating pre-set table, so we have it positioned as a screening instrument," he said. "Also, this is not a covered service under managed care. While we recommend the test, we tell patients we charge a fee, and they may decline the test if they wish."
The screening visual field, he said, takes less than 1 minute per eye, and patients can see the printout immediately. Justifying the cost of adding a perimeter to a practice is a valid, important issue, Dr. Clompus said, and practitioners should evaluate just how many adult patients they have who could benefit from visual field testing.
In the end, Dr. Clompus said, visual field tests "prevent me from missing a disease I may not have picked up with normal exam techniques."
Faster, more accurate perimetry
Dr. Kirstein has used an Octopus 1-2-3 perimeter from Interzeag since 1990. "It has run virtually all day long, every day," he said.
Compared to other perimeters he is familiar with, Dr. Kirstein said, the Octopus 1-2-3 is user-friendly and runs quickly, and patients are more comfortable with its ergonomic design. "As opposed to bowl perimetry, it's a little less threatening to the patient," he said.
Dr. Kirstein has recently started using Interzeag's Tendency Oriented Perimetry, or TOP, for full threshold testing. "It's fast and uses smart questions by allowing the perimeter to ask fewer questions, but more of the right questions," he said. "We can take a 15-minute test and reduce it to 3 minutes per eye for a full threshold test."
In his practice, Dr. Sherman uses the Dicon LD-400 perimeter, which also features Dicon's FieldLink. "It's helpful because it allows you to do the test and create a file simultaneously, which shortens the length of time of the entire procedure," he said.
Dr. Sherman said the Dicon perimeter is both user- and patient-friendly and offers shorter testing time, which patients prefer. "The results are quite good and reliable," he said, "and patients are impressed with the 3-D hill of vision because they understand when their visual field is getting worse."
Dr. Clompus also uses a Humphrey perimeter. "What's nice about threshold visual fields is that the tests are getting faster," he said. "And we now have technology, called SWAP (short wavelength automated perimetry), that can sometimes pick up glaucoma and neurological disease 3 to 5 years earlier than a white-on-white test."
He said the speed of visual field tests parallels technological advancements. "It used to take 15 minutes, then with FastPac it took 8 minutes, and now with SITA (Swedish Interactive Threshold Algorithm) it takes about 4½ minutes," Dr. Clompus said. "So these things have permitted our Humphrey unit to become more effective."
Objective perimetry?
What does the future of perimetry hold? According to Dr. Sherman, the possibility exists of developing objective perimetry — a quantum leap, he said, from recent advances that have brought faster tests into the doctor's office.
"If someone could work out an appropriate protocol for performing evoked potential testing, which would be an analysis of brain waves, it would be more rapid and precise than what we're doing now," Dr. Sherman said. "We certainly have evoked potentials in other areas of testing, but we haven't worked it out yet to do objective visual fields to a degree to which people are satisfied."
Dr. Clompus would also like to see an objective visual field test developed, but first he would like to see a full threshold test that can be performed in less than 1 minute. "If we go one more step, let's make it an objective test rather than subjective," he said. "The patient would just have to look at a target, and the instrument would know how they responded."
What all clinicians are looking for, Dr. Kirstein said, is "the perfect test to tell us exactly what's wrong, how long it's been there and what we should use to treat it."
For Your Information:
- Richard Clompus, OD, may be contacted at 1450 E. Boot Road, Unit 700B, West Chester, PA 19380; (610) 696-1368; fax: (610) 430-2079. Dr. Clompus has no direct financial interest in any of the products mentioned in this article, and he is a paid consultant for Humphrey Instruments.
- Elliott M. Kirstein, OD, may be contacted at 11304 Montgomery Road, Cincinnati, OH 45249; (513) 530-0440; fax: (513) 530-0473; e-mail: EKirst1016@aol.com. Dr. Kirstein has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any company mentioned.
- Jerome Sherman, OD, may be contacted at SUNY College of Optometry, 100 East 24th Street, New York, NY 10010; (212) 780-5004; fax: (212) 780-5207. Dr. Sherman has no direct financial interest in any of the products mentioned in this article, and he is a paid consultant for Dicon.