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Wendy W. Harrison, Marcus A. Bearse, Jr., Glen Y. Ozawa, Marilyn E. Schneck, Kavita P. Dhamdhere, Shirin Barez, Anthony J. Adams; Retinal Function In Type 2 Diabetes Patients Who Develop Macular Edema: A Longitudinal Pilot Study. Invest. Ophthalmol. Vis. Sci. 2012;53(14):372.
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We have shown that the mfERG, along with other health factors, is a sensitive predictor of diabetic edema (DE) in an at-risk patient group. However, it is unclear how these factors change as diabetic macular edema (DME) develops. In this pilot study, we examine changes in retinal and visual function in a group of type 2 diabetes patients before and after DME development.
A small high-risk group of type 2 diabetes patients (one eye each, n=7; aged 55.2 ± 9.3 years) was followed every 6-12 months until DME developed. All had high HbA1c (10.4 ± 2.4%) and long disease duration (14.5 ± 6.6 years). All had diabetic retinopathy (DR) and no DME at the first visit (v1); all eyes had DME onset at the second visit (v2). mfERG, (VERIS 5.2) , blood pressure (BP), fundus photos, visual acuity (VA), contrast sensitivity (CS), and HbA1c were obtained on all patients at both visits. mfERG implicit times (IT) and amplitudes (Amp) were normalized to Z-scores based on 52 controls, and grouped into 35 zones. Differences between v1 and v2 were evaluated.
VA, CS, and HbA1c remained unchanged from v1 to v2 (p =0.30; 0.33; and 0.47 respectively). VA was good for all patients (95 ± 6 letters; 20/25) but CS, although unchanged, was reduced (1.46 ± 0.12 log CS) at both visits. BP improved v1 to v2 (141/83 to 128/75; p<0.02). Three eyes had retinopathy that clinically worsened between visits. Overall, IT became more delayed from v1 to v2 (p <0.05) and Amp trended toward decreasing (p = 0.08). These mfERG changes were uniform across the retina, and not limited to the edematous areas. In other words, regions which did and did not develop edema worsened at similar rates (0.67/0.50 IT Z-scores; 0.63/0.49 Amp Z-scores respectively).
The early fundoscopic appearance of mild DME does not seem to result in significant changes in VA in this pilot group. CS was depressed before DME developed and was not altered by DME onset. The mfERG neural function is locally abnormal in patients with DR before edema develops and continues to worsen diffusely across the entire central retina (not only locally), as diabetic disease progresses.
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