Abstract
Purpose:
To learn how the multifocal electroretinogram (mfERG) and vision function change over time in eyes that present with diabetic macular edema (DME).
Methods:
Ten eyes of 10 patients with type 2 diabetes were studied at the time of DME diagnosis (V1) and 6 to 12 months later (V2); none were treated for the edema during the study period. Subjects were 58.4 ± 6.8 yrs old with mean diabetes duration of 14.4 ± 5.4 yrs and poor glucose control (HbA1c ≥ 8.2). All subjects had moderate to severe non-proliferative diabetic retinopathy (DR) and DME diagnosed by fundus evaluation by a retina specialist at V1, and DR with or without DME at V2. Fundus photos, visual acuity (VA), low contrast VA (LCVA), contrast sensitivity (CS), color vision (CV) and mfERG were obtained at both visits. Each eye’s 103 mfERG implicit times (IT) and amplitudes (AMP) were converted to Z-scores (ITz and AMPz) based on 52 control eyes. These were segregated into 2 zones per eye: (1) An “Edema zone” of retinal locations with DME at V1 and (2) “NoRet zone” of locations free of any retinopathy lesions at V1 and V2. Average V1 and V2 ITz and AMPz were calculated for each zone and compared using paired t-tests.
Results:
At V2, clinical signs of DME disappeared partially or completely in 8 eyes, remained clinically steady in 1 eye and worsened in 1 eye. At both visits, mean IT in Edema zones was significantly worse (P < 0.005) than NoRet zones (mean ITz for NoRet and Edema zones are respectively, 1.37 ± 0.36 and 2.06 ± 1.09 at V1, 1.56 ± 0.48 and 3.79 ± 1.34 at V2). At both visits, mean AMP in Edema zones was significantly worse (P < 0.05) than NoRet zones (mean AMPz for NoRet and Edema zones are respectively, -0.63 ± 0.61 and -2.07 ± 0.97 at V1, -0.94 ± 0.72 and -3.08 ± 1.02 at V2). IT and AMP worsened from V1 to V2 (P < 0.05) in Edema zones but remained unchanged in NoRet zones. Interestingly, V1 mfERGs in Edema zones that resolved clinically from V1 to V2 continued to deteriorate further (P < 0.001). VA, LCVA and CS remained unchanged from V1 to V2 (all P > 0.16), though CV worsened (P < 0.05).
Conclusions:
Disappearance of clinically visible signs of DME is not associated with improved VA, LCVA and CS but CV worsens. mfERG IT and AMP worsen over time in locations with edema regardless of change in clinical status of edema over 6 to 12 months.
Keywords: 505 edema •
499 diabetic retinopathy •
509 electroretinography: clinical