Abstract
Purpose :
In this ongoing study we are using flash and pattern electroretinography (fERG and pERG) to clarify the contributions of retinal signaling abnormalities to previously reported changes in contrast sensitivity, visual acuity, and contour integration in people with schizophrenia.
Methods :
Data were collected on 24 patients and 25 age-matched healthy controls. fERG data were collected under both light- and dark-adapted conditions, using a range of flash intensities, backgrounds, and temporal frequencies. The primary fERG variables of interest were a-wave activity (reflecting photoreceptor response), b-wave activity (reflecting primarily bipolar cell activity) and the photopic negative response (PhNR) (reflecting ganglion cell activity). The primary pERG variables of interest were magnitude, magnitude D, and the magnitude D/magnitude ratio for low and high contrast stimuli.
Results :
On photopic fERG tests, schizophrenia patients demonstrated significantly weaker photoreceptor response when a flash was presented against an unlit background (p<.05), and during a steady-state flicker test (p<.005). On scotopic tests, the rate of response gain per unit of intensity increase was significantly weaker for patients than controls (group x condition interaction p=.001). In both light- and dark-adapted conditions, patients demonstrated weaker signaling of bipolar cells (ps < .005). The schizophrenia group was also characterized by a weaker PhNR (p<.05). Multiple tests' a- and b- wave amplitudes were related to behavioral contrast sensitivity impairments in the schizophrenia group (ps < .05 or .001), but not to visual acuity or contour integration. The groups did not differ significantly on pERG variables. For patients only, significant relationships were observed between poorer contour integration and reduced pERG amplitudes and longer latencies (all ps either < .05 or .001). For controls only, higher pERG values were related to better near and far visual acuity (ps < .05 or .01).
Conclusions :
These data suggest that both reduced signaling of photoreceptor and bipolar cells, as well as attenuated response gain, are associated with schizophrenia. Both rod and cone responses appear to be affected, and these changes may be related to the contrast sensitivity reduction in this group. The issue of ganglion cell function in schizophrenia is less clear, but its relationships to contour integration warrant further study.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.