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- Title
Rod-Dominated OP Responses Enhance Detection of Early Retinal Dysfunction in STZ-Diabetic Rats.
- Authors
Thule, Peter M.; Kim, Moon K.; Olson, Darin E.; Cheng, Haiying; Nair, Govind; Dong, Timothy Q.; Pardue, Machelle T.
- Abstract
Diabetic retinopathy (DR) is typically diagnosed during late stages. Electroretinograms (ERG) permit non-invasive evaluation of retinal function by selectively recording rod and cone responses to graded light stimulation, and could hasten diagnosis of DR if diagnostic criteria could be developed. Diabetes mellitus perturbs implicit times (IT) and amplitudes of the oscillatory potentials (OP), inner retinal cell generated signals embedded in standard ERG readings. However, the time course of these changes remains unclear. We evaluated serial ERG over 29 weeks in diabetic Sprague-Dawley rats using a commercial ERG system. Dark-adapted ERG were recorded from a range of flash stimuli (-3.4 to 2.1 log cd see/m2) at baseline, 5, 9, 14, 20, and 29 weeks in diabetic (DM) (n=17) and non-diabetic (Con) (n=l 5) age matched animals. OP were extracted from the ERG tracings off-line using a 75-300 Hz filter. OP amplitudes fluctuated widely and tended to diminish over time in both DM and Con. In contrast, IT prolongation, expressed as % baseline, was observed consistently, but only among DM. After 5 weeks, IT prolongation was seen only with the lowest, rod-dominated stimulation intensity (-3.4 log cd sec/m²). Nine or more weeks were required to reveal prolonged IT with intermediate stimulation (3.0 to -1.2 log cd see/m²), whereas 20 or more weeks of elevated blood glucose were required to prolong IT in response to more cone-dominated stimuli (> -0.6 log cd sec/m²). We conclude that OP analysis can detect inner retinal rod pathway impairment after as little as 5 weeks in STZ-rats. In general, low-intensity, rod-dominated responses were more sensitive in detecting IT prolongation than high-intensity cone-dominated responses. Of note, high-intensity, cone-dominated stimuli are currently used to record OP responses clinically. Thus, examining OP generated by dim flashes may be a better indicator of early dysfunction in DR.
- Subjects
ELECTRORETINOGRAPHY; OSCILLATIONS; DIABETIC retinopathy; DIAGNOSIS of eye diseases; EYE examination
- Publication
Diabetes, 2007, Vol 56, pA219
- ISSN
0012-1797
- Publication type
Article