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Marilyn E Schneck, Wayne A Verdon, Kavita P Dhamdhere, Taras V Litvin, Wendy Lam, Marcus A Bearse, Anthony J Adams; Associations between ganzfeld ERG responses to photopic 30 Hz flicker and dark-adapted oscillatory potentials in Type 2 diabetes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4420.
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We explore possible associations between scotopic ERG oscillatory potentials and photopic 30 Hz flicker responses to ISCEV standard 3.0 cd/s.m2 ERG stimuli. Second, we re-examine 30 Hz flicker responses in eyes of diabetics without diabetic retinopathy, with non-proliferative diabetic retinopathy (NPDR), and diabetic macular edema.
63 persons with type 2 diabetes [28 without retinopathy (NoRet); 26 with NPDR (NPDR); 9 with NPDR and diabetic macular edema (DME)] and 23 visually normal non-diabetics (Non-Diab) participated. After pupil dialation and 20 min dark adaptation, ERGs were recorded to the ISCEV standard scotopic flash to derive OPs. After 10 min light adaptation to a 36 cd/m2 background, ISCEV standard photopic 30 Hz flicker responses were recorded. LKC software was used to measure flicker AMP and IT and to isolate OPs. Cursors were placed manually on OPs and peak-trough amplitudes (AMP) and peak implicit times (IT) of the first 4 OPs were determined.
For all diabetics as a group, 30 Hz flicker AMP was significantly correlated with AMPs of all 4 OPs and summed OP AMP (P <0.0001). For NoRet, only OP1 AMP is significantly associated with 30 Hz AMP (P<0.001). For NPDR, OPs 1,3 and 4 and summed AMP are significantly associated with 30 Hz flicker AMP (P<0.001). Associations (r2=0.42-0.44 for OPs 1-3) between OP AMP and 30 Hz AMP observed in the small DME group were not significant. For all diabetics as a group, 30Hz flicker IT was significantly correlated with OP1, OP2, and OP3 IT (P <0.0005). OP1 IT is significantly correlated with 30 Hz IT in all 3 diabetic groups (P<0.005). OP 2 and OP3 IT are correlated with 30 Hz IT only in NoRet (P<0.0005). In Non-Diab, there was no significant association between flicker AMP and OP AMPs or between flicker IT and OP ITs. IT of OPs 1,2 and 4 differed significantly between groups (P<0.0001). OP ITs were significantly delayed in DME compared to all other groups (P<0.01). In contrast, flicker IT and AMP did not differ between eyes of diabetic and non-diabetic subjects.
There are significant associations between ISCEV standard photopic 30 Hz flicker and scotopic flash OPs in diabetes, but not in Non-Diab eyes. In contrast to some reports, we find the photopic flicker ERG to be relatively insensitive to diabetes and non-proliferative diabetic eye disease.
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