My interest in glaucoma diagnostic devices started early in my career during a Fellowship at Tufts, and has only increased with time. I’ve held positions as Director of Glaucoma at UPMC and the University of Arizona School of Medicine, and as a faculty member at Yale University School of Medicine. You could say I’m infinitely curious about how to detect the disease earlier, treat the disease more effectively, and manage my patients to maintain their ability to see. So when I was introduced to pattern electroretinography (ERG) as a practice-based vision test, my curiosity took over. Here’s what I knew from my previous experience:
- ERG is a functional test.
- ERG is an objective test.
- ERG test results measure both cells that are “alive” and those that are “suffering.”
- Several studies had shown ERG results to be useful in identifying glaucoma early.
- ERG was not practical to use in an everyday office setting.
Here is what I know now that I’ve used ERG in private practice:
The use of ERG is most beneficial in glaucoma suspects. This is a technology that allows us to diagnose or confirm glaucoma earlier than anything else that we currently use.
When we use visual fields results for diagnosis, the visual field defects are based on cells that are already dead, so the damage has already happened. When we use OCT results the same thing occurs: thinned nerve fiber layer = dead/lost cells. We know structural damage detected with OCT precedes visual field changes. There are studies that show pattern ERG precedes OCT changes by eight years. So office-based ERG technology has really become a very useful tool in my practice to accelerate and confirm early glaucoma diagnosis, treat our patients sooner, and identify the at-risk patients much earlier.
The second best benefit next to early detection is measuring function for patient management. Because ERG measures all living cells, both those functioning well and those functioning not-so-well, we have the ability to treat the suffering cells and improve function. We don't want to wait for people to have structural damage (dead cells) because we can't bring that back, but we can modulate and improve visual function in these patients.
For instance, we had a glaucoma patient come in for testing with pressures of 25 and her pattern ERG results showed dysfunction. We adjusted her drops, and set a follow-up for 6 months. On her return visit, her pressures were lower, and her ERG results showed improved function with better waveforms and quantitative data. We were able to show that patient that lowering her pressures was a good thing. As a bonus, these results help patients stay compliant when they can “see” their improvements on the reports.
To summarize, I’ve known for a while that objective, functional results from electroretinography could be beneficial in diagnosing glaucoma early. What I’ve learned is that these tests are now readily accessible to doctors like me in private practice, and the ERG test results are not just helpful for diagnosis, but are helpful in tracking treatment efficacy and disease progression. My curiosity continues.
- Robert J. Noecker, MD, MBA
Ophthalmic Consultants of Connecticut
The Diopsys® NOVA™ is an electrophysiology device that generates photic stimuli, and records, processes, and analyzes the resultant signals to provide information about the visual system. This article represents the experiences and opinions of Dr. Robert Noecker. Physicians should make medical decisions based on the individual facts and history of each patient.
What have you learned over your career that has changed the way you diagnose or treat your patients? Let us know in the comments below!