Abstract
Purpose: :
The ocular disturbances associated with diabetes mellitus, diabetic retinopathy and macular edema, are the leading causes of blindness in developed countries. A growing body of evidence now demonstrates that the retinal pigment epithelium (RPE) is affected in diabetes (cf., Shirao & Kawasaki 1998). Electro-oculograms of diabetic patients with and without retinopathy display reductions in all components (fast oscillation, light peak, dark trough). Furthermore, diabetic rats exhibit structural disturbances in the RPE characterized by thickening of basal lamina of the RPE and Bruch’s membrane, deepening of basal infoldings in the RPE, and formation of large vacuoles within the RPE accompanied by cellular swelling. We have applied an electroretinogram (ERG)-based technique to determine the time-course over which the light evoked responses of the RPE change during the course of diabetes mellitus.
Methods: :
B6 mice were injected with streptozotocin (STZ) to induce hyperglycaemia and diabetes. We used ERG-based techniques to measure the light evoked components of the RPE (dc-ERG) and the neural retina (a-wave, b-wave).
Results: :
STZ-injected mice developed hyperglycaemia (defined by blood glucose greater than 250mg/dl) one week post injection. At 4 weeks post-injection a- and b-wave amplitudes of STZ mice were reduced as compared to controls. All components of the dc-ERG were reduced, with the largest reduction seen in the fast oscillation component.
Conclusions: :
RPE function is disrupted at an early stage in the STZ-induced mouse model of diabetic retinopathy. By facilitating early detection of diabetic retinopathy, the non-invasive dc-ERG measurement may be a useful outcome measure for monitoring therapeutic interventions.
Keywords: diabetic retinopathy • retinal pigment epithelium • electroretinography: non-clinical