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Marilyn Schneck, Wayne Verdon, Wendy Lam, Kavita Dhamdhere, Tina Zeng, Shirin Barez, Marcus Bearse, Anthony Adams; Relation between the fast oscillation of the EOG and ERG measures of rod photoreceptor function in healthy eyes and in diabetes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5108.
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© ARVO (1962-2015); The Authors (2016-present)
The fast oscillation of the EOG (FO) is an RPE-generated response to periodic light stimulation that is secondary to rod activity. Both the FO and rod function are often abnormal in people with diabetes (Schneck et al, 2008, Holopigian et al, 1997). We examined whether reductions in the FO can be related to altered rod photoreceptor function in individuals with diabetes.
Data from the right eyes of 34 healthy controls and 26 people with diabetes are considered (12 without retinopathy, and 14 with NPDR in the test eye). Pupils were fully dilated. FO was recorded using an LKC UTAS 2000 system modified to measure the FO, skin electrodes at the medial and lateral canthi (forehead ground), and one-minute light/one-minute dark cycles. Eye movements were processed offline using a new method of template fitting to entire individual eye movements to obtain the FO, resulting in cleaner fits of the FO. Following the FO, after 20 minutes of dark adaptation, dark- and light-adapted full field ERGs were recorded to an intensity series of brief flashes (spanning ~ 2.5 log units) using gold bipolar contact lens electrodes. Light-adapted cone ERGs were subtracted from dark-adapted responses to obtain isolated rod responses. Rmax and S parameters of the rod a-wave of the ERG were derived after Hood and Birch.
FO amplitude was significantly reduced in diabetics (p=0.006) as in Schneck et al, (2008). In controls, rod log Rmax was significantly correlated with FO amplitude (p=0.008); this association was not seen in diabetes (p=0.34). Further, as has been reported, Rmax was not reduced in diabetes compared to controls (p=0.85), though log S was (p=0.00003), here even in those with no retinopathy in either eye (p=0.005). Log S was not associated with FO amplitude in controls (p=0.52) nor in those with diabetes (p=0.54). Log S was significantly related to blood glucose in those with diabetes (p=0.004).
In healthy controls, log Rmax is significantly correlated with the FO amplitude, but not in people with diabetes despite no difference in log Rmax between normals and diabetics. The reduction in FO amplitude seen in diabetes is not associated with changes in the a-wave indices of rod function. Thus diabetes may disrupt the normal association between log Rmax and the FO via intrinsic RPE disruption rather than through photic (rod) dysfunction.
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