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."
- 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
- 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
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
- 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.
- 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
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.
- Healthy individuals underwent PERG and Flicker ERG testing protocols
- Test–retest repeatability of protocols was calculated using intraclass correlation coefficients (ICC)
- 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
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.
- Eyes with preperimetric glaucoma; manifest glaucoma; and normals were examined
- PhNR and PERG tests were run on all eyes
- Both PhNR and PERG performed similarly to detect glaucoma
- PhNR has the advantage of not requiring clear optics and refractive correction
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