This article is more than 5 years old. Information may no longer be current.
Perimetry: Not just for screening and managing glaucoma
Click Here to Manage Email Alerts
NEW YORK — The uses for perimetry have increased beyond diagnosing and managing glaucoma patients, according to J. James Thimons, OD. Screening visual fields can help ODs detect and manage other vision problems in addition to glaucoma.
"Perimetry has a vital role in today's optometric practice," said Dr. Thimons, chair of the department of clinical sciences at the State University of New York College of Optometry. "Even if you do not have a glaucoma practice or screen a significant number of patients for glaucoma, a visual field device is valuable for an initial evaluation and also for long-term management."
Although Dr. Thimons reserves full-threshold visual screening for specific patients — those who have unexplained changes in vision, complain of headaches or have any type of neurological deficit — he routinely performs a baseline screening visual field on diabetics; patients with a history of trauma to the globe, retinal damage, congenital or hereditary diseases; and patients with mild elevations in intraocular pressure.
"This is not a test that's overused. It's probably used less than it should be," Dr. Thimons said. "We see many glaucoma patients, but we also do visual fields in pediatric cases, for sudden losses of vision, transient vision loss and neurological complaints. These all need a visual field to determine the fact that the visual system is normal."
Dr. Thimons also uses perimetry because of medicolegal issues. "I do not do this routinely, but on occasion I use the visual field to verify what I saw in an exam," he said, "so I have a physical test that confirms my findings."
Improved care, increased revenue
Perimetry has improved care, Dr. Thimons said, by allowing optometrists to test for subtle changes within the visual system.
"There is also an ability to generate an appropriate level of revenue relative to this process," he said. "What happens, though, is that doctors use the full-threshold capacity of the device when the majority of their patients are just as well served by the screening phase, where the test is shorter and the reimbursement for that level of testing is consistent with the time spent."
Optometrists who can perform five to 10 screening visual field tests per week, a number that Dr. Thimons said is not extraordinary, will generate more than enough revenue to offset leasing payments and the cost of operating the equipment. And since nearly all of the perimetry systems available today have both full threshold and screening capabilities, the issue becomes when should screening visual fields be performed.
Jerome Sherman, OD, SUNY Distinguished Professor and a private practitioner, said a strong case can be made for performing routine screening visual fields.
"Routine screenings have a place in detecting retinal problems, optic nerve problems other than glaucoma and problems that affect the visual pathway," Dr. Sherman said. "I am an advocate of it. I don't say it has to be done to meet the standard of care, but it is in the patient's best interest."
A screening visual field, which is not invasive and is quick to perform, can help you detect an abnormality that other tests, such as magnetic resonance imaging and computed tomography, can confirm.
Visual fields can also help optometrists pick up retinal disease, Dr. Sherman said. "Not appreciated by most doctors is an entity called occult retinal disease," he said. In situations where the retina looks normal during an examination, visual fields can initially detect a problem. Further testing, such as electroretinography (ERG), go beyond visual fields to confirm retinal disease.
William Jones, OD, director of optometric education at the Albuquerque V.A. Medical Center, said visual fields can also be used to detect maculopathy and nerve fiber defects.
"We use visual fields for glaucoma all the time, but other indications include malingering, tilted disc or optic disc hypoplasia; documenting visual field loss due to ptosis; or documenting legal blindness," Dr. Jones said.
Faster, easier equipment
Improvements in visual field instruments have made it easier for optometrists to use a routine screening field as a tool of discovery, said Ron Banfiel product manager at Dicon Inc. "We are seeing a change in attitude towards the value of performing routine visual field screening resulting from our perimetry innovations," he said. "We are trying to heighten the awareness that when you do a visual field, you are measuring the entire visual pathway."
Today's instruments are simpler, faster and easier to use, Mr. Banfiel said, and he tells doctors that early detection and early treatment are more cost effective than simply measuring damage that has occurred. "If a doctor thinks a more extensive visual field test is needed, it can be done on the same instrument that performed the screening field," he said.
The time it takes to complete a full-threshold test may soon be reduced with the introduction of an algorithm from Humphrey Instruments that uses artificial intelligence to complete the test in about one-third the time it takes conventional machines.
"Many doctors use visual fields as a screening process, and, particularly in the older patient population, something may become evident with the visual field exam that was not found during the routine exam," said Rob Foster, senior product manager for glaucoma products at Humphrey.
He said practitioners using SITA report the ability to perform previously unscheduled visual fields at time of service and that SITA reduces the amount of perimetry overhead, improving on the number of visual field exams performed and the margin on each exam.
For Your Information:
- William Jones, OD, can be contacted at 2100 Ridgecrest SE, Albuquerque, NM 87108; (505) 265-1711. Dr. Jones had 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 contacted at 100 East 24th St., New York, NY 10010; (212) 780-5004. Dr. Sherman is a paid consultant for Dicon.
- J. James Thimons, OD, can be contacted at 100 East 24th St., New York, NY 10010; (212) 780-5007. He has no financial interest in any of the products mentioned in this article, nor is he a paid consultant for any company mentioned.
- Ron Banfiel can be contacted at (520) 527-1939; fax: (520) 527-4589.
- Rob Foster can be contacted at (800) 227-1508; fax: (510) 297-4775.
- Dicon Inc. can be reached at (619) 554-1770; fax: (619) 554-0332.
- Humphrey Instruments can be reached at (800) 423-4393; fax: (510) 297-4319; e-mail: info@ humphrey.com.
Indications for automated perimetryVisual field exams are indicated for some of the following reasons other than glaucoma:
|