Major Finding: Larger central retinal venular diameter is an independent and early indicator of progression to proliferative diabetic retinopathy with or without high-risk characteristics in black patients with type 1 diabetes mellitus.
Data Source: A 6-year follow-up evaluation of a cohort of 468 black patients from the New Jersey 725 study.
Disclosures: The authors had no financial disclosures. The research was supported by grants from the National Eye Institute and by a Lew Wasserman Merit Award from Research to Prevent Blindness Inc.
Central retinal venular diameter may help predict the progression of retinal disease in black patients with type 1 diabetes, especially those with less-severe baseline diabetic retinopathy, according to Dr. Monique S. Roy of the New Jersey Medical School, Newark, and her colleagues.
These results may lead to another early clinical indicator for progression to more severe forms.
Dilation of the retinal venules has been associated with diabetic retinopathy (DR), but cross-sectional studies have not indicated whether these changes simply reflect disease severity or may help predict progression of DR.
The investigators examined 725 black patients with type 1 diabetes who participated in the New Jersey 725 study in 1993-1998, and reexamined a cohort of 468 of these patients 6 years later (Arch. Ophthalmol. 2011;129:8-15). The exams included seven-field retinal photographs that were evaluated in a masked fashion.
In the 468 follow-up patients, the mean central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were 168.8 mcm and 254.2 mcm, respectively. The study found no association between CRAE and incident DR outcomes, even after adjustment for other risk factors. However, increasing CRVE at baseline was associated with triple the risk of progression to proliferative diabetic retinopathy, or to PDR with high-risk characteristics, even when researchers adjusted for other risk factors.
“The relative dilation of the retinal veins seen in DR and other retinopathies associated with ischemia has been variously interpreted,” the researchers pointed out. “Wider retinal venules may reflect metabolic changes associated with [diabetes mellitus], such as increased lactic acidosis.”
Strengths of the study include its prospective design with high rates of follow-up for a large cohort of well-characterized black patients with type 1 diabetes, the use of standardized protocols to document potential confounding variables, the masked grading of DR using stereoscopic seven-field retinal photographs, and measurements of the retinal vascular diameters with a validated computerized program, Dr. Roy and her associates said.
However, they cautioned that measurement of retinal vessel diameter from color retinal photographs may underestimate the true vascular width because only the red blood cell column is being measured. Also, the increased retinal pigmentation that is present in blacks may lead to an overestimation of retinal diameter sizes.
“It remains to be seen whether such a measure may be used in the future to monitor treatments for [diabetes] and other vascular diseases that specifically target the microvasculature,” the researchers noted.
In an accompanying editorial, Dr. Tien Yin Wong of the Singapore Eye Research Institute stated that larger retinal venular diameter or a generalized venular dilatation may help predict the progression of diabetic retinopathy, even after accounting for other known risk factors (Arch. Ophthalmol. 2011;129:95-6).
Although the underlying mechanisms are unclear, the researchers suggested that retinal venous dilatation may indicate ocular ischemia, systemic inflammation, and/or endothelial dysfunction, added Dr. Wong, who had no financial disclosures.