Rapid dilation of retinal vessels in response to flickering light (functional hyperemia) is a well-known autoregulatory response driven by increased neural activity in the inner retina.1,2 The altered dynamic equilibrium between energy demand from neurons and energy supply from blood may in turn influence retinal ganglion cell (RGC) function. Using the steady-state pattern electroretinogram (SS-PERG), a sensitive measure of RGC function in response to counterphase flickering gratings, it has been demonstrated that RGC normally autoregulate their activity as shown by a progressive reduction of SS-PERG amplitude by about 30% (adaptation) over 4 minutes.3 The ability of SS-PERG to adapt may be reduced or absent in conditions affecting RGC function such as glaucoma or optic neuritis.4,5
Using and optimized protocol for assessment of SS-PERG adaptation over 2 minutes,6 Salgarello and collaborators7 performed a pilot cross-sectional study on 28 treated glaucoma patients (11 early-to-moderate, 17 pre-perimetric) and 17 age-matched normal subjects. Both SS-PERG amplitude and SS-PERG amplitude adaptation were significantly reduced in patients compared to controls (p < 0.01) on average. The area under the receiver operating characteristic (AUROC) to distinguish glaucoma patients from normal subjects was 0.87 for SS-PERG amplitude adaptation and 0.76 for SS-PERG amplitude. Thus, the inclusion of SS-PERG amplitude adaptation improved detection of glaucomatous RGC dysfunction compared to SS-PERG amplitude alone.
The inclusion of SS-PERG amplitude adaptation improved detection of glaucomatous RGC dysfunction compared to SS-PERG amplitude alone
This study adds to the rich literature on the usefulness of PERG assessment to detect early glaucomatous RGC dysfunction, accentuating the significance of including adaptation in PERG protocols to improve sensitivity and gain insight on RGC autoregulation.