Purpose:
To evaluate the ability of Pattern Electroretinogram (PERG), a measure of retinal ganglion cell (RGC) function, to predict future worsening of optic disc damage in patients suspected of glaucoma.
Methods:
PERGs (PERGLA paradigm) were measured every 6 months in patients suspected of glaucoma (n=427) over an average of 28 (SD=18) months. During the observation period, a subgroup of patients (n=56) developed deterioration of optic disc cupping. Hazard ratios for predicting time-to-worsening of optic disc cupping were obtained by Cox proportional regression model. Post-hoc Kaplan-Meier analysis was done on cases stratified in three groups based on the amount of PERG amplitude/phase deficit from normal (no deficit; moderate deficit; severe deficit).
Results:
Patients with more delayed phase at baseline had a significantly earlier time to worsened optic disc (p=0.003, Cox proportional hazards regression). Fifteen ms of delay was associated with a 51% higher risk of progression (95% CI:15% to 98%). Post-hoc analysis stratified cases into three severity groups: delayed 17.1 ms or more (n=116), delayed < 17.1 ms (n=209), and not delayed (n=100). Those with delayed phase had a higher incidence of optic disc worsening (see figure, p=0.002). PERG amplitude had a similar, albeit insignificant trend (Cox regression p=0.18).
Conclusions:
In our population of glaucoma suspects, an abnormal PERG phase at baseline was highly predictive for future worsening of optic disc cupping. These findings are consistent with the hypothesis that RGC become dysfunctional before loss of optic nerve tissue in early glaucoma.
Keywords: ganglion cells • electroretinography: clinical • optic disc