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Diopsys Insights

What ERG Looks Like Today: A Roundup of Studies

Posted by Diopsys, Inc. on January 6, 2020 at 1:43 PM

More than two decades ago, electroretinography (ERG) was used by academics and others outside of the eye care professional’s office for research studies conducted in university labs and other academic centers. Expensive, cumbersome, and complex, this testing method was restricted to certain users and environments and required the use of invasive equipment that was less than ideal for patients.

Today, ERG testing is not only much more user-friendly for both patients and technicians, but it can be carried out in the office in less than ten minutes. With upgraded functionality and effectiveness in a variety of everyday applications supported with new studies, ERG is now seeing increased use in the eye care community.

If you’re still unfamiliar with how others are using ERG technology, review some of the key takeaways from these informative resources on one of the most valuable assets in an eye care practice today.

Reproducibility of Flicker ERG in Patients with NPDR

One observational study has evaluated the reproducibility of flicker ERG in patients with nonproliferative diabetic retinopathy (NPDR) and found that in-office flicker ERG parameters are highly reproducible and negatively correlate with retinal ischemia in NPDR. This suggests that global retinal dysfunction could be reliably quantified earlier in patients with diabetes, and results could possibly help clinicians "decide when to initiate anti-VEGF therapy in eyes with mild-to-moderate NPDR, as well as when to extend the treatment interval and eventually discontinue treatment."

The Details:

  • Ultra-widefield fluorescein angiography (UWF-FA) performed on patients with mild-to-moderate NPDR
  • UWF-FA images graded by the Fundus Photography Reading Center in WI, USA
  • Fixed- and multi-luminance flicker ERG repeated four times

The Results:

  • UWF-FA showed 82.5% and 17.5% of eyes had mild and moderate NPDR
  • Fixed-luminance phase values were highly reproducible
  • Significant negative correlation between fixed-luminance phase and log-corrected ischemic index values

Read the Study: Reproducibility of Fixed-luminance and Multi-luminance Flicker Electroretinography in Patients With Diabetic Retinopathy Using an Office-based Testing Paradigm

Flicker ERG for Tracking Anti-VEGF Treatment

Diagnostic tests that can reveal retinal function changes can be useful in tracking treatment success of anti-VEGF therapy. One study examines the influence of ranibizumab on flicker ERG results in diabetic eyes with macular edema and showed that:

  • Flicker ERG implicit time improved significantly between baseline and final follow-up
  • The shortened flicker ERG implicit time might imply that ranibizumab has no negative impact on the entire peripheral cone function, but can improve it instead

The Details

  • Diabetic eyes with no or background diabetic retinopathy and macular edema were included
  • Three examinations were performed: at baseline, 4 weeks after the first injection, and 4 weeks after the last injection
  • Visual acuity (Snellen and ETDRS chart), fasting blood glucose, OCT, multifocal ERG and full field ERG-flicker were measured at all three examinations. In addition, fluorescein angiography was performed at baseline.

The Results

  • There was no correlation between the reduction in OCT from baseline to follow-up and change in visual acuity
  • Cone implicit time with flicker ERG improved significantly between baseline and follow-up
  • There was no significant change in amplitude or implicit time in mfERG

Read the Study: Peripheral retinal function assessed with 30-Hz flicker seems to improve after treatment with Lucentis in patients with diabetic macular edema

Repeatability of PERG and Flicker ERG

Many ocular diseases, including glaucoma and diabetic retinopathy, may display an erratic or slow pattern of progression, which makes the test–retest repeatability one of the most important features of vision tests included in clinical management strategies. A study out of Wills Eye Hospital evaluated the repeatability of the PERG and full-field flicker ERG.

The Details

  • Healthy individuals underwent PERG and Flicker ERG testing protocols
  • Test–retest repeatability of protocols was calculated using intraclass correlation coefficients (ICC)

The Results

  • PERG and Flicker ERG protocols were shown to have good-to-excellent test–retest repeatability
    (Note: ICC values between 0.75 and 0.90 are considered good and greater than 0.90 excellent)
  • ICCs for the PERG parameters ranged from 0.793-0.911
  • ICCs for the flicker ERG parameters ranged from 0.968-0.944

Read the Study: Test–retest repeatability of the pattern electroretinogram and flicker electroretinogram

Detecting Glaucoma with Electrophysiological Markers

There are two main electroretinography vision tests that measure retinal ganglion cell function: the photopic negative response (PhNR) and pattern electroretinogram (PERG). Both electrophysiological markers are reduced in glaucoma. One study compared these two early markers for glaucoma - PhNR and PERG - in different stages of disease.

The Details:

  • Eyes with preperimetric glaucoma; manifest glaucoma; and normals were examined
  • PhNR and PERG tests were run on all eyes

The Results:

  • Both PhNR and PERG performed similarly to detect glaucoma
  • PhNR has the advantage of not requiring clear optics and refractive correction

Read the Study: Photopic Negative Response versus Pattern Electroretinogram in Early Glaucoma

Still curious about the use of ERG technology? Learn more in a free eBook from Diopsys and Ophthalmology Times on the role that objective, functional results from ERG testing have in value-based management decision-making. “A Game-Changer in Diabetic Retinopathy” by Steven M. Silverstein, MD also discusses:  

  • The benefits of ERG in relation to other diagnostic tools
  • Current patient acceptance of modern ERG testing
  • The clinical applications of pattern and flicker ERG

Get eBook >>

ERG Studies

 

Topics: Glaucoma, Pattern ERG, Flicker ERG, Diabetic Retinopathy, ffERG/PhNR

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As the world leader in modern visual electrophysiology, Diopsys, Inc. has done more than any other company to advance the use of ERG and VEP in the eye care practice. Read through our blog to gain valuable insights into the benefits and integration of this valuable technology.

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