Asymmetric Diabetic Retinopathy and Carotid Insufficiency: A Correlative Study

Abstract
Background: Diabetic retinopathy occurs in both type 1 and type 2 diabetes mellitus and has been shown that nearly all type 1 and 75% of type 2 will develop diabetic retinopathy after 15 years duration of diabetes as shown in epidemiological studies. In western population, diabetic retinopathy has been shown to be the cause of visual impairment in 86% of type 1 diabetic patients and in 33% of type 2 diabetic patients [1].
Aim of Study: To detect a relationship between carotid system insufficiency and the presence of asymmetric diabetic retinopathy in diabetic patients.
Patients and Methods: A descriptive cross sectional non-controlled non-randomized study was carried between August 2011 and March 2012 on 20 patients with asymmetric diabetic retinopathy graded and documented with fundus fluorescein angiography (FFA). Assessing the carotid system patency and flow parameters using duplex Ultrasound was then done. Primary outcome was to find a correlation between the diabetic retinopathy asymmetry and carotid system insufficiency in terms of presence of atheromtous plaque, increased intima media thickness (IMT) or decreased flow parameters.
Results: 50% of cases had a degree of carotid insufficiency. The degree of carotid insufficiency in either common carotid artery and/or internal carotid artery ranged from 15% to 50% stenosis. And 10% had increased IMT and 15% had increased RI all on the ipsilateral side of the eye with more advanced diabetic retinopathy. And an overall 45% increase in IMT.
Conclusion: Asymmetric diabetic retinopathy is considered to be the exception rather than the rule as DR is usually symmetric. We found that Carotid stenosis is a contributing factor in causing such asymmetry. So presence of asymmetric DR urges early investigation for detecting carotid system insufficiency and carotid plaques to avoid future strokes.