Article Date: 10/1/2010

Diagnose Glaucoma with Confidence

Diagnose Glaucoma with Confidence

Tests including scanning laser polarimetry and visual fields give you all the "expert opinion" you need.

Joseph Sowka, OD, FAAO, Diplomate

Practitioners who want to treat more glaucoma, add a subspecialty, or enhance their diagnostic capabilities typically start to weigh their technology needs. In addition to having applanation tonometry, fundus photography, corneal pachymetry, and gonioscopy in your toolkit, it's essential to incorporate automated threshold perimetry and an imaging device such as scanning laser polarimetry or optical coherence tomography. These tests help us detect optic nerve loss and match it against the functional effects of glaucoma.

From a practice management perspective, adding these technologies is neither expensive nor cumbersome, and they allow doctors to diagnose with conviction and bill for the tests — two keys to a practice's success.

Getting an "Expert Opinion"

Which patients are candidates for scanning laser polarimetry? In my glaucoma practice, the answer is all of them. In a general practice, doctors can use the technology to assess patients with known glaucoma, as well as patients with ocular hypertension or other suspects.

In general practices, a scanning laser polarimeter can provide an "expert opinion." Some glaucoma specialists may not use imaging technology because they're comfortable evaluating the retinal nerve fiber layer (RNFL) clinically. In a general practice, doctors are usually less comfortable making this judgment. With a scanning laser polarimeter, practitioners don't need to rely on clinical evaluation of the RNFL alone. The technology gathers and analyzes the pertinent data, providing a confidence building "expert opinion."

I use the GDxPRO (Carl Zeiss Meditec) scanning laser polarimeter. This robust technology quantifies the RNFL very precisely. The technology even removes some of the artifact seen in previous models for patients with high degrees of myopia or a lightly pigmented fundus.

The analyses on the GDxPRO printouts help specialists and general practitioners alike diagnose glaucoma with confidence. The clear, easy-to-read reports present the RNFL data numerically and graphically in a symmetry analysis. Additionally, a glaucoma progression analysis for patients being followed over time is under review for regulatory approval.

In addition to this very high-resolution assessment of the RNFL's thickness and integrity, the GDxPRO compares a patient's data to normal and glaucoma eyes in its database. It uses these data to arrive at a number called the Nerve Fiber Indicator (NFI), which is related to the likelihood that a patient's RNFL is abnormal. I get a clear picture of the quantity and quality of the RNFL, and so can any general practice optometrist.

What's more, the GDxPRO is fast and stores a great deal of data. It's simple to acquire an image — the whole process takes about 5 minutes — and staff can be trained quickly to perform the test.

Side-by-Side Structure and Function

The next step is to see how the scanning laser polarimetry correlates with other findings like the optic nerve appearance, intraocular pressure, patient history and visual fields. Together, these data give us the complete clinical picture of glaucoma.

For visual field testing, I use the Humphrey Field Analyzer (HFA, Carl Zeiss Meditec), but the Humphrey Matrix (Carl Zeiss Meditec) is an excellent choice for general practices since it has very robust capabilities with a lower price and a smaller footprint.

The highly sensitive Matrix tests visual fields using a method called frequency doubling technology (FDT), an excellent choice for glaucoma management because it reveals loss of sensitivity in the magnocellular pathways affected by the disease. The easy-to-read printout (similar to that of the HFA) shows the locations of functional decline in the visual fields. In patients with glaucoma, these locations typically correspond to those of RNFL loss illustrated by the GDxPRO. The Matrix stores test data and enables practitioners to retrieve and analyze tests for long-term management.

From a practical perspective, the Matrix is fast, easy to use and flexible where it is set up for testing. With very little training, staff members can perform the test. It's very easy to align the eyes and get an accurate test. For patients, the experience is quick and comfortable — about 30 seconds for screening and 5 minutes for threshold tests — and there's no eye patch. The Matrix doesn't require a darkened room, so you can put it anywhere, and it's compact.

The Financial Benefits

In addition to the clinical advantages of these technologies and their relatively easy adoption into a general practice, there are also financial advantages to expanding your ability to diagnose and manage glaucoma. You're keeping patients in your practice instead of referring them to a specialist. These are long-term patients who will need regular testing and treatment for years.

The scheduling and billing for these additional visits may take some getting used to. When a patient comes into a general practice for a comprehensive exam, the doctor performs the exam and bills appropriately. If routine tests or examination show that the patient has ocular hypertension or some other feature such as a suspicious disc appearance that makes him a glaucoma suspect, or if it's already clear that the patient has glaucoma, then insurance coverage goes from the vision plan to the health plan.

The doctor then needs the patient to return for visual field testing, gonioscopy, a second intraocular pressure measurement and structural imaging. However, one followup visit usually isn't enough. We reschedule diagnostic imaging based on the patient's insurance because many carriers do not pay for imaging procedures like scanning laser polarimetry, OCT and dilated fundus photos performed the same day. Scheduling them separately may sound awkward, but it's entirely appropriate because it enables us to get multiple pressure tests on different days and times. And by the end of this initial series of exams, we have a bigpicture view of the patient's status, which enables us to develop an informed treatment plan.

General practices already have most of what they need for glaucoma diagnosis and management. And with easy-to-incorporate scanning laser polarimetry and threshold perimetry, they gain an extra "expert opinion" and the ability to combine structure and function in clinical practice. It's what keeps patients with their doctor long term, which in turn builds practices.

Dr. Sowka is a Professor at Nova Southeastern University College of Optometry in Fort Lauderdale, Fla., where he serves as Chief of the Advanced Care Center and Director of the Glaucoma Service. He is a Diplomat of the American Academy of Optometry's Disease Section, Glaucoma Subsection.

Incorporating GDxPRO and Humphrey Matrix Into Your Practice

Humphrey Matrix
Affordable and valuable: This affordable technology provides sensitive detection of visual field loss in the cells that are most susceptible to damage from glaucoma.
Easy to use, easy to read: Any staff member can use this device with brief training, and the reports are clear and simple for busy practitioners.
Space saving: The Matrix is portable and it doesn't need a dim room like some visual field devices.
Fast and friendly: Screening tests take about 30 seconds, which keeps patients moving efficiently. Patients feel comfortable with the machine, as well, and it doesn't require an eye patch.

Easy to use and read: Staff members are easily trained to use this technology, particularly because its automatic pupil alignment doesn't require a great deal of experience. Scanning is fast. And because the live fundus view helps ensure the right fixation, the well-designed, easy-to-read reports make it easy for practitioners to see problems at a glance.
Efficient workflow: The GDxPRO's portable design means you can use the device virtually anywhere in the practice or in multiple practices, and a "lockdown" feature protects the optics while you move it. Data portability is possibly more impressive. Easily print data, store data in standard file formats and network with other devices.

Optometric Management, Issue: October 2010