An Objective Appraisal
Pattern electroretinography device aids in definitive diagnosis.
PETER KEHOE, O.D., F.A.A.O.
My partner, Brian Platt-ner, O.D., and I installed the Diopsys NOVA-VEP, an office-based visual evoked potential device, more than two years ago, and it helped revolutionize the way we diagnose and treat our glaucoma patients. Its success in our practice led to the addition of Diopsys’ NOVA-ERG (pattern electroretinography), which has made a huge difference for diagnosing and monitoring many other conditions.
Similar to the VEP, which objectively measures the function of the entire visual pathway, the ERG measures the functionality of the retina. By incorporating the ERG in addition to the VEP, now we can precisely determine whether a problem is located along the visual pathway or at the ganglion cell level.
The ERG does not replace visual field testing or an OCT. Rather, it helps us find clinical information that impacts the way we treat our patients.
This objective functional measurement of the retinal function at the ganglion cell level allows us to make an early diagnosis and to monitor degenerative diseases, such as glaucoma, AMD and diabetic retinopathy, as well as neurological conditions, such as multiple sclerosis and amblyopia.
The ERG uses a ground electrode on the forehead and two NOVA-ERG lid sensors placed on the lower eyelids, which act as the active or reference electrode (depending on what eye is being tested). The patient looks at a series of patterns or bars on the screen and focuses on the fixation target in the center. Each test takes less than a minute, and the total test time is 10 to 15 minutes.
For example, we use the Concentric Stimulus Fields protocol for an objective functional study of a focal disease, such as diabetic edema and AMD.
Usually, we don’t schedule the test with a comprehensive exam. We’ve found patient flow is better when we schedule it separately along with other specialized tests that are not typically part of a comprehensive exam. However, we’ll perform the test on the same days as the exam if we feel it is necessary.
We’ve had no pushback from our patients who have used the ERG, and they have said Diopsys’ lid technology is very comfortable, and the test is fairly easy for them to understand.
The operator view of the NOVA-ERG is shown on the left. Patients observe a series of patterns or bars and focus on a center fixation target (right).
Staffing is always a concern when incorporating new technology into any office — we want to make sure we’re getting accurate, consistent results. Initially, Diopsys came to our office and trained us for two days. Now, our office manager is able to teach the device to new hires, which they’ve found easy to understand. If I need a test done, any of our technicians can pick it up even if they haven’t done the test in a month.
We bring back patients on a regular basis for follow-up visits because the ERG vision test allows us to pick up subtle changes. Overall, we average about 1.5 tests per year through our whole patient population.
Also, we are the only practice within 100 miles with electrodiagnostic capabilities, so we see just about everyone in our area who has suspicious visual issues or symptoms, such as MS and receive referrals about once every two weeks from the neurologists in town.
NOVA-ERG is the highest-reimbursed procedure that we perform. Medicare pays $154.00 for ERG in our area. Also, we get full reimbursement for both the ERG and VEP when we do them on the same day. In addition, the CPT codes are not mutually exclusive, so you can perform the test with others whose codes are not mutually exclusive.
Space in a practice can also be very expensive, especially in metropolitan areas. The Diopsys NOVA takes up less than 4 feet by 7 feet — in an office with high cost per square foot, that’s huge.
A game changer
The Diopsys NOVA-ERG can easily be incorporated into your office, and it provides clinical information that truly impacts the way we treat our patients. It’s patient friendly, and is one of the highest reimbursed procedures in the practice and has been a game changer for our office. OM
Optometric Management, Volume: 49 , Issue: May 2014, page(s): 74, 75