Associations Between Contrast Sensitivity And Multifocal Electroretinograms In Type2 Diabetes

Abstract

Purpose: : To examine the relationship between contrast sensitivity (CS) and the multifocal electroretinogram (mfERG) in adult patients with type 2 diabetes mellitus (T2DM).

Methods: : Single eyes of 40 adult T2DM patients without retinopathy (NoRet group), 28 with mild to moderate non-proliferative diabetic retinopathy (NPDR group) and 46 controls were studied. Their mean ages were 53.6± 8.5, 53.3± 7.7 and 49.7± 11.4 yrs for the NoRet, NPDR and control groups, respectively. T2DM duration was 7.7± 4.0 for the NoRet group and 8.0± 3.8 yrs for the NPDR group. All the subjects had 20/20 or better visual acuity. CS was tested using Pelli Robson charts. mfERGs were recorded and local N1-P1 amplitude (AMP) and P1 implicit time (IT) were derived using a template scaling technique (Hood & Li 1997). 45 deg fundus photos were graded for all subjects to identify the presence and location of NPDR. T-tests were performed to examine whether the subject groups differed. CS was compared to IT and AMP within two zones: C1 (the center mfERG from 0-1.2 deg eccentricity) and C2 (the average of 7 mfERGs from 0-4.5 deg eccentricity) using linear regression.

Results: : CS was significantly different between all subject groups (P<0.001). CS in the NPDR group was lowest, despite the fact that only 2 of these 28 patients had a lesion within the central 2.4 deg. IT in the NoRet and control groups did not differ in both zones. However, the NPDR group had significantly longer IT than the other groups in both zones (P<0.001). In the two zones, the NoRet and NPDR groups had similar AMP but were significantly lower than the controls (P<0.001). CS was negatively correlated with IT in both retinal zones in the NPDR group (P<0.001) but not in the other groups. CS was not correlated with AMP in any groups.

Conclusions: : Longer mfERG IT in the central retina is significantly correlated with reduced contrast sensitivity in adults with T2DM and NPDR. This was observed even though most of the retinopathy was mild NPDR and the central retina was retinopathy free in majority of the cases. It will be interesting to monitor CS in NoRet patients who will develop NPDR in the future and to examine possible associations with mfERG.

Keywords: diabetes • electroretinography: clinical • contrast sensitivity