Quantitative assessment of early diabetic retinopathy using fractal analysis.
OBJECTIVE
Fractal analysis can quantify the geometric complexity of the retinal vascular branching pattern and may therefore offer a new method to quantify early diabetic microvascular damage. In this study, we examined the relationship between retinal fractal dimension and retinopathy in young individuals with type 1 diabetes.


METHODS
We conducted a cross-sectional study of 729 patients with type 1 diabetes (aged 12-20 years) who had seven-field stereoscopic retinal photographs taken of both eyes. From these photographs, retinopathy was graded according to the modified Airlie House classification, and fractal dimension was quantified using a computer-based program following a standardized protocol.


RESULTS
In this study, 137 patients (18.8%) had diabetic retinopathy signs; of these, 105 had mild retinopathy. Median (interquartile range) retinal fractal dimension was 1.46214 (1.45023-1.47217). After adjustment for age, sex, diabetes duration, A1C, blood pressure, and total cholesterol, increasing retinal vascular fractal dimension was significantly associated with increasing odds of retinopathy (odds ratio 3.92 [95% CI 2.02-7.61] for fourth versus first quartile of fractal dimension). In multivariate analysis, each 0.01 increase in retinal vascular fractal dimension was associated with a nearly 40% increased odds of retinopathy (1.37 [1.21-1.56]). This association remained after additional adjustment for retinal vascular caliber.


CONCLUSIONS
Greater retinal fractal dimension, representing increased geometric complexity of the retinal vasculature, is independently associated with early diabetic retinopathy signs in type 1 diabetes. Fractal analysis of fundus photographs may allow quantitative measurement of early diabetic microvascular damage.
Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Australia. dannycheung@hotmail.com
Ning
N
Cheung
Kim C
KC
Donaghue
Gerald
G
Liew
Sophie L
SL
Rogers
Jie Jin
JJ
Wang
Shueh-Wen
SW
Lim
Alicia J
AJ
Jenkins
Wynne
W
Hsu
Mong
M
Li Lee
Tien Y
TY
Wong
D000293:Adolescent; D017668:Age of Onset; D001315:Australia / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000453:epidemiology / Q000503:physiopathology*; D005260:Female; D017709:Fractals; D007839:Functional Laterality; D006801:Humans; D008297:Male; D010781:Photography; D015995:Prevalence; D012161:Retinal Artery / Q000503:physiopathology*; D012169:Retinal Vein / Q000503:physiopathology*; D012720:Severity of Illness Index; D055815:Young Adult