Learning the ABCs of ERG:

Your Unanswered Questions from June's Peer Learning Session

By Timothy Earley, OD

One of the things I enjoy most about serving on the optometric clinical advisory team for LKC Technologies is the opportunity to connect with my colleagues to share, learn, and grow as we navigate the implementation of modern ERG, best practices, and the amazing utility of the RETeval^®. One such opportunity is ABCs of ERG, a quarterly question-and-answer session held online for peers to share their experiences and ask questions about the device.

Oftentimes, the conversation is so lively that we aren’t able to address everything asked, especially the questions that are written in the chat. That was the case for the ABCs of ERG session held on June 7^th – it was a great conversation with lots of questions asked, but the hour was short and many of the questions from the chat were left unaddressed by the general discussion. The questions and answers below came from ABCs of ERG participants, with some input from the LKC team.

How do you decide which patients to test?

I test glaucoma suspects, all of my patients with diabetes, and early pre-AMD patients to get a baseline measurement.
We test patients with hypertensive retinopathy, AMD, diabetes, and glaucoma.
I use it with my glaucoma patients and ocular hypertensives.

How repeatable is it? Should I test my patients just once per year, or twice?

Frequency of testing is based on medical necessity. Initial full-field ERG (ffERG) is recommended for patients with any diabetic retinopathy (DR) at baseline to establish a comparator if future DR worsening is detected subsequently. The ffERG is recommended for patients who demonstrate structural DR worsening over time (via clinical exam or imaging) equivalent to a 2-step Diabetic Retinopathy Severity Scale (DRSS) change (e.g., going from mild to moderate NPDR, or moderate to moderately severe or severe NPDR) as follows:

Patients with any DR who demonstrate a DR Score (result of the DR Assessment protocol on the RETeval device) ≥ 23.5 should be referred to a retina specialist, particularly if NPDR severity is moderate or worse.
Patients with DR Score ≥ 23.5 with what appears, clinically, to be mild NPDR, should be monitored closely or considered for referral to a retinal specialist to confirm appropriate staging of DR severity.
Patients with a DR Score ≥ 26 should be referred to a retina specialist.
Patients with a DR Score ≤ 23.5 with mild or moderate NPDR should have repeat examination every 6-12 months, including repeat measure of ffERG and DR Score.
Patients with mild or worse NPDR with DR Score ≥ 21 should be considered for repeat ffERG/clinical exam within 6-12 months to assess for worsening severity of structural or functional abnormalities.

For diabetic patients who score greater than 23.5 on the DR Assessment on the RETeval device, what diagnosis codes can be used to bill?

There are multiple codes that can be used. Oftentimes, patients will fall under more than one category, such as venous engorgement, unexplained visual disturbance, etc.
There is a code for “failed functional testing,” which means that if your patient responds in the yellow or red reference range, you can use that code for necessary follow-up testing.

Consult the ERG Coding and Reimbursement Guide for more details >

Can the RETeval be used to monitor patients taking Plaquenil?

American Academy of Ophthalmology guidelines for monitoring Plaquenil toxicity includes multifocal ERG (mfERG), which gives a more detailed report on separate quadrants of the retina and macula. The RETeval device does not have mfERG capabilities, but the UTAS™ by LKC Technologies does.

At what point in the progression of glaucoma would you expect to see changes in PhNR?

Typically, dysfunction occurs prior to structural damage. ERG testing will often show abnormal results before structural tests show cell loss.
Because functional loss occurs first, any patient suspected of having glaucomatous optic atrophy should have a baseline PhNR test performed.

When evaluating for glaucomatous optic atrophy, the manual says that if the PhNR is > 100 ms implicit time and the b wave amplitude is reduced, there is an issue. The 100 ms implicit time still can come up green. Any other thoughts for glaucoma?

Follow the bottom portion of the test report (PhNR at minimum) to follow for ganglion cell changes.
Use the patient’s baseline (1^st test) to compare to subsequent tests to monitor for changes.
In unilateral diseases, look for differences between the eyes.
Just like all types of biological functioning, there’s a range of what is considered “normal.” I hope that patients fall into the 50^th percentile or better. When test results show that my patients are in the 10^th percentile or worse, I am more concerned even if the color-coded reports show that the results are still within the statistical “normal” range. The only way we know which way the tissue is trending is to follow the gross data over time, rather than the color on the interpretation report.

What codes are being used on glaucoma suspects?

We use glaucomatous optic atrophy (H47.233).

Consult the ERG Coding and Reimbursement Guide for more details >

Do ERG results bottom out at some point, similar to how OCT can become less useful in end-stage glaucoma?

ERG will still pick up information even in late-stage glaucoma. ffERG measures full field retinal responses and tests a larger degree of the retina than the OCT will pick up.

Does anyone have experience using the RETeval with retinitis pigmentosa (RP)?

I would recommend running the dark-adapted protocol for RP patients. Rod dysfunction typically occurs in early disease stages, followed by cone dysfunction in later disease stages.

I have 9 years’ worth of data on a different ERG device. Is there a way to use that data with the data from a RETeval?

Even on devices that can perform the same test, the calculations, electrodes, waveform structures, reference ranges, and proprietary algorithms can differ. For that reason, you would want to perform a baseline test with the RETeval, and continue testing with that device to monitor for changes over time. The RETeval also provides a unique parameter, the DR score, which can be used to track changes over time.

I understand the RETeval has a VEP protocol. What is VEP testing used for?

Visual evoked potential (VEP) is good for children, non-verbal patients, concussion protocols, and nerve defects.
VEP can also be helpful to identify neurological issues, especially for patients with unexplained visual disturbances, malingering, TBI, MS, and stroke patients. An ERG can identify retinal dysfunction, but the VEP looks at everything from the optic nerve to the visual cortex. VEP and ERG have separate CPT codes and can be run on the same day and billed separately. Consult the ERG and VEP Coding and Reimbursement Guides for more details.
When testing children, a big advantage of the RETeval device is that one eye can remain uncovered. Excessive eye movement can interfere with test results, so a child can be entertained during testing, such as by watching a video on a parent’s lap with the untested eye.

Will the RETeval have multifocal ERG capabilities in the future?

Currently, you would need the sistema UTAS, developed by LKC Technologies, as it offers mfERG as well as pattern-based testing.
I’m not sure what future functionality might be integrated into the RETeval.

Interested in Learning More From Your Peers?

Join us for our next ABCs of ERG session! This quarterly event is open to experienced RETeval users, those looking for help getting started, or anyone in between. This is not a webinar, but an opportunity for you to talk to other eye care providers about your trials and triumphs as you work to leverage the power of functional testing for your patients. Bring your questions and share your success as we engage in a lively discussion led by Timothy Earley, OD.

About the Author

Timothy Earley, OD

Medina Vision and Laser Center (Medina, OH)

Dr. Timothy Earley joined Medina Vision and Laser Centre in 1998. He was born and raised in Honesdale, PA and earned his Bachelor’s degree in Biology from the University of Scranton. He earned his Bachelor’s degree in Visual Science and his Doctorate in Optometry from the Pennsylvania College of Optometry. Dr. Earley is a national speaker and consultant on electroretinography, age-related macular degeneration, and serves on the editorial advisory board of Optometric Management.

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Learning the ABCs of ERG:

Your Unanswered Questions from June's Peer Learning Session

Interested in Learning More From Your Peers?

About the Author

Timothy Earley, OD

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