Inter-Eye Agreement in Measurement of Retinal Vascular Fractal Dimension in Patients with Type 1 Diabetes Mellitus

ABSTRACT

Purpose: To investigate inter-eye agreement in retinal vascular fractal dimension (F_D) in patients with type 1 diabetes.

Methods: In a cross-sectional study, both eyes were exained in 178 patients with type 1 diabetes. All vessels in a zone 0.5–2.0 disc diameters from the optic disc were traced and F_D calculated with the box-counting method using SIVA-Fractal semiautomatic software. The modified Early Treatment Diabetic Retinopathy Study (ETDRS) scale was used to grade diabetic retinopathy (DR). Pitman’s test of difference in variance was used to calculated inter-eye agreement in F_D according to level of DR.

Results: Mean age and duration of diabetes was 37.0 years and 29.5 years, respectively, and 49.4% of participants were male. Mean F_D of right and left eyes was 1.4540 and 1.4472, respectively. F_D did not differ between eyes in patients with no or non-proliferative DR (NPDR) in both eyes. This was true for patients with the same level of DR in both eyes (n = 74, p = 0.73), as well as for patients in which the ETDRS level of DR between the eyes differed by 1 (n = 43, p = 0.99) or more (n = 9, p = 0.53). In patients treated for proliferative DR in one eye, F_D was significantly lower in this eye compared to the other (n = 10, p = 0.03).

Conclusion: F_D did not differ significantly between the two eyes of patients with no DR or NPDR, despite differences in severity of DR.

KEYWORDS:

• Agreement
• correlation
• diabetic retinopathy
• fractals
• retinal vascular fractal dimension
• type 1 diabetes

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Funding

This study was supported by Fight for Sight, Denmark, the Synoptic Foundation, Medivit Aps, the Gangsted Foundation, the Foundation of Karen Svankjaer Yde, Lykfeldts Grant, the A.P. Moeller Foundation for the Advancement of Medical Science, the Region of Southern Denmark, and the University of Southern Denmark.

Additional information

Funding

This study was supported by Fight for Sight, Denmark, the Synoptic Foundation, Medivit Aps, the Gangsted Foundation, the Foundation of Karen Svankjaer Yde, Lykfeldts Grant, the A.P. Moeller Foundation for the Advancement of Medical Science, the Region of Southern Denmark, and the University of Southern Denmark.