Editor’s note: Advancements in electrophysiological technology can help ophthalmologists to discover vision-related diseases in their earliest stages. In this article, Blake K. Williamson, MD, shares how use of a vision testing system has made a difference in his practice as a cataract specialist, whereas William E. Sponsel, MD, shares his perspective as a glaucoma specialist.
Using PERG in patients with cataracts
Electrophysiology sounds a little like Frankenstein in a mad laboratory; it’s not nearly as sexy as femtosecond lasers or real-time aberrometry. In addition, it has historically been a time-consuming test that required an electrophysiologist to interpret results.
However, pattern electroretinography (PERG) has been around much longer than optical coherence tomography (OCT) images and the literature leaves little doubt as to its accuracy.
The development of new sensors and advanced algorithms has made it a compact diagnostic machine which is easy to have in the office, and a test that a technician can comfortably perform with well-interpreted results.
The vision testing system (Diopsys NOVA Vision Test System, Diopsys) we use can be compared with my smartphone: its uses are limitless, and I use it for early diagnosis of glaucoma and gauging treatment efficacy.
As a cataract specialist, I regularly see patients with some indications of glaucoma, but no definitive diagnosis.
Maybe they have ocular hypertension (OHT) but no sign of disc cupping or visual field loss, or maybe they have a suspicious disc, but their IOP does not draw attention.
Evaluating cell function
PERG provides an objective evaluation of the function of the retinal ganglion cells, permitting the diagnosis of glaucoma up to 8 years earlier than with other methods of diagnosis.
An even better scenario is when PERG results indicate that I can take a patient off hypotensive drops. In some cases, the pressure seemed to be so high that a patient was put on drops. However, after observing their excellent cell function, I am able to take them off their drops and clear up any dryness or ocular surface disease.
My partners and I believe that PERG evaluation is a significant enough advantage for our patients that we have purchased units and perform testing in all four of our offices.