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Laurence Shen Lim, Peng Guan Ong, E SHyong Tai, Gemmy Chui Ming Cheung, Wallace S Foulds, Tien Y Wong; Changes in retinal vessel caliber with flicker light stimulation in eyes with diabetic retinopathy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3014.
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Changes in retinal vessel calibre in response to flickering light are believed to be mediated by nitric oxide release from the retinal microvascular endothelium. This study investigated the responses of retinal vessels to flickering light in diabetic patients with various grades of diabetic retinopathy(DR).
This cross-sectional observational study evaluated adult subjects with diabetes mellitus. The Dynamic Vessel Analyser (DVA) was used to measure retinal vascular responses to diffuse illuminance flicker. DR was graded from retinal photography. Each eye was assigned a retinopathy severity score according to the modified Airlie House classification system, and categorized as minimal nonproliferative diabetic retinopathy (NPDR), mild NPDR, moderate NPDR, severe NPDR, or proliferative retinopathy. Eyes were also classified as having any DR (minimal NPDR or worse), moderate DR (moderate NPDR or worse), or vision-threatening DR (severe NPDR or worse, or clinically significant macular edema) according to the Eye Diseases Prevalence Research Group definitions.
There were 279 subjects in total, with a mean age of 59.9±9.2 years. The majority were male (73%) and the mean HbA1c level and mean duration of diabetes were 7.7±1.4% and 13.9±10.4 years respectively. After adjustments for age, sex, smoking, duration of diabetes, HbA1c, hypertension and hyperlipidemia, retinal arteriolar and venular dilation responses to flicker stimulation decreased continuously with increasing severity of diabetic retinopathy.(p = 0.008 and <0.001 respectively). Subjects with reduced arteriolar dilation responses were more likely to have any DR [odds ratio (OR) 1.20 (95% confidence interval 1.01 - 1.45) per standard deviation (SD) decrease, p=0.045]. Subjects with reduced venular dilation responses were more likely to have any DR [OR 1.27(1.04 - 1.53) per SD decrease, p=0.02], moderate DR [OR 1.27 (1.06 - 1.49) per SD decrease, p = 0.007] and vision-threatening DR [OR 1.51(1.14 - 1.50) per SD decrease, p = 0.002].
Retinal arteriolar and venular dilation responses to flickering light are diminished in subjects with DR, and decrease progressively with more severe stages of DR. Our findings suggest that the severity of DR is correlated with measurable differences in retinal microvascular endothelial function, supporting a role for the latter in the pathogenesis of DR.
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