The Incomparable Value of Objective Functional Testing in Patients with Diabetes

Contributions by:

Francis Bynum, OD; Nathan Lighthizer, OD, FAAO; Julie Rodman, OD, MSc, FAAO

As the leading cause of blindness in working-age adults, diabetic retinopathy is typically asymptomatic until patients experience significant structural damage, long after the disease initially develops. For this reason, an objective test that provides optometrists with clear metrics can help with decision-making and provide insight into whether a patient can be managed in-house or should be referred out to an ophthalmologist or retinal specialist. In addition, functional changes have been shown to precede structural changes seen via dilated eye examination or retinal imaging, especially in prediabetes.[1] As such, for patients who might have diabetic retinopathy—in which early detection is crucial to vision preservation—functional testing may facilitate earlier detection and treatment that could alter a patient’s quality of life for decades. In fact, research has suggested that ERG testing may have the highest predictive value in forecasting the progression of diabetic retinopathy.[2],[3]

We need to know as much about function as we do about structure in patients with diabetes; but both visual acuity testing and visual fields are subjective tests that rely on patient feedback,” says Francis Bynum, OD, of Northwest Tennessee Eye Clinic in Martin, TN. “An ERG test provides objective information on the function of the visual system and it gives reliable guidance for medical professionals to manage functional changes that may impact a patient’s vision, typically in advance of structural changes.”

ERG Is an Easy-to-Use, Objective Technology

Modern, handheld ERG technology is nothing like the wires and corneal electrodes that were used in labs in decades past. Today’s technology is supremely simple and practical, offering very clear reporting. For example, the RETeval device is handheld, portable, and can test retinal function non-invasively, quickly, and prior to clinical examination through undilated pupils. It is appropriate for all patients, at any age, without any need for sedation or special training. In fact, technicians can easily perform the test so that results are ready for the doctor to review with patients during the clinical examination. We can run a RETeval DR Assessment in minutes,” says Nathan Lighthizer, OD, of Oklahoma College of Optometry. “It’s faster than refraction.”

The RETeval device flashes a series of lights into the patient’s eyes. The retina then responds to the flashes by generating small, electrical signals that travel through the facial structure to the sensor strips placed on the lower eyelid. When following the diabetic retinopathy protocol, RETeval sensor strips detect the electrical signals and will compare the results to an age-adjusted diabetic retinopathy reference database.


The Benefits of an ERG-generated DR Score

“The RETeval device is unique in that it offers a DR Assessment protocol that provides a risk assessment for progression,” notes Julie Rodman, OD, MSc, of Nova Southeastern. “As diabetic patients worsen into moderate and severe nonproliferative disease, it may become challenging to determine the best time to refer to a retinal specialist, but with the RETeval DR Assessment, you simply check the score.” A score of 23.5 or higher indicates an 11-fold risk of requiring intervention within 3 years.[4]

This is an important feature of ERG testing—it allows us to detect functional stress so that we can anticipate structural damage,” adds Dr. Bynum. “Functional tools like ERG can provide clear answers and allow us to confidently make clinical decisions, particularly when we’re treating diabetic retinopathy.”

Protecting Patients and Growing Practices

There is no question that ERG is a benefit to patients who have diabetes. In fact, in studies comparing ERG and structural imaging’s abilities to evaluate sight-threatening diabetic retinopathy, RETeval ERGs outperformed the traditional imaging techniques in predicting which patients would later need medical intervention. [5],[6] But the RETeval device impacts bottom lines in more ways than one. There are 560 ICD-10 codes to choose from when coding for ERG and the national average reimbursement is $128.09 as a bilateral test. The most commonly used CPT code is 92273, electroretinography (ERG) with interpretation and report.


[1] Ratra D, Nagarajan R, Dalan D, Prakash N, Kuppan K, Thanikachalam S, Das U, Narayansamy A. Early structural and functional neurovascular changes in the retina in the prediabetic stage. Eye (Lond). 2021 Mar;35(3):858-867. doi: 10.1038/s41433-020-0984-z. Epub 2020 May 28. PMCID: PMC8026633.

[2] McAnany JJ, Persidina OS, Park JC. Clinical electroretinography in diabetic Surv Ophthalmol. 2022 May-Jun;67(3):712-722. doi: 10.1016/j.survophthal.2021.08.011. Epub 2021 Sep 4. PMCID: PMC9158180.

[3] Brigell M, Davis Q, Waheed N. Predictive Value of ERG, OCT-A, and UWF-FA in Patients with Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4038.

[4] Brigell MG, Chiang B, Maa AY, Davis CQ. Transl Vis Sci Technol. 2020;9(9):40. doi:10.1167/tvst.9.9.40

[5] Brigell MG, Chiang B, Maa AY, Davis CQ. Transl Vis Sci Technol. 2020;9(9):40. doi:10.1167/tvst.9.9.40

[6] Al-Otaibi, H., Al-Otaibi, M. D., Khandekar, et al. (2017). Translational Vision Science & Technology, 6(3), 3-3.