Early Visual Deficits in Streptozotocin-Induced Diabetic Long Evans Rats

• Type of Material: Article
• Authors: Peter Thule, Emory University; Darin Olson, Emory University; Machelle Pardue, Emory University; MH Aung, Emory University; MK Kim, Emory University
• Language: English
• Date: 2013-02-01
• Publisher: Association for Research in Vision and Ophthalmology (ARVO)
• Publication Version: Final Published Version
• Copyright Statement: © 2013 The Association for Research in Vision and Ophthalmology, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1167/iovs.12-10927
• Title of Journal or Parent Work: Investigative Ophthalmology & Visual Science
• ISSN: 0146-0404
• Volume: 54
• Issue: 2
• Start Page: 1370
• End Page: 1377
• Keywords: Science & Technology; BLOOD-FLOW; RETINAL DYSFUNCTION; MICE; ABNORMALITIES; VISION; MOUSE MODEL; RETINOPATHY; OSCILLATORY POTENTIALS; SYSTEM; Ophthalmology; CONTRAST SENSITIVITY; Life Sciences & Biomedicine

Abstract

Purpose. Although diabetic retinopathy (DR) is clinically diagnosed based on vascular pathology, diabetic patients with angiographically normal retinas have been found to exhibit subtle defects in vision. This has led to the theory that diabetes-associated metabolic abnormalities directly impair neural retinal function before the development of vasculopathy, thereby resulting in visual deficits. In this study, we sought to delineate the temporal relationship between retinal dysfunction and visual deficits in a rat model of Type 1 diabetes. Moreover, we investigated the relative contribution of retinal dysfunction versus diabetes-induced lens opacity, to the visual deficits found in early-stage DR. Methods. Pigmented Long Evans rats were rendered diabetic with streptozotocin (STZ). Control and diabetic rats were assessed across 12 weeks of hyperglycemia for visual function with optokinetic tracking weekly visual acuity and monthly contrast sensitivity, retinal function with darkadapted electroretinograms (monthly electroretinograms [ERGs]), and cataract formation with slit lamp exam (biweekly). Results. Diabetic rats exhibited significantly reduced visual function and delayed ERG responses by 1 month post-STZ. Significant cataracts did not develop until 6 weeks post- STZ. Moreover, increases in lens opacity (r =-0.728) and ERG implicit times (r =-0.615 for rod-dominated response and r = -0.322 for rod/cone mixed response) showed significant correlations with reductions in visual acuity in diabetic rats. Conclusions. STZ-induced hyperglycemia reduces visual function, affecting both visual acuity and contrast sensitivity. The data suggest that visual defects found in early-stage DR may initially involve abnormalities of the neural retina and worsen with later development of cataracts. © 2013 The Association for Research in Vision and Ophthalmology, Inc.