Abstract
Purpose: :
To map and quantify site-specific changes within the vascular tree of the human retina during progression of non-proliferative diabetic retinopathy (NPDR). Previous in vivo studies using various angiogenesis models have shown that endogenous stimulators, inhibitors and therapeutics such as VEGF, bFGF and triamcinolone acetonide induce site-specific ‘fingerprint’ changes in vascular pattern within remodeling vascular trees and networks. These alterations in vascular pattern were mapped and quantified by the software VESGEN (VESsel GENeration).
Methods: :
For prospective evaluation of retinal vascular patterns in patients with NPDR, binary (black/white) arterial and venous trees were isolated from 50° digital fluorescein angiograms by semi-automatic computer processing. Major vascular parameters were mapped and quantified by VESGEN including fractal dimension (Df), vessel diameter (Dv), tortuosity (Tv) and densities of vessel area, length, number and branch point (Av, Lv, Nv and Br). The software automatically segments the vascular tree into branching generations (G1,…,Gx) according to changes in vessel diameter and bifurcational branching.
Results: :
Eight to nine branching generations (G1 to G8 or G9) were mapped and quantified by VESGEN software within the arterial and venous trees of 2 patients with mild/moderate and severe NPDR. In arterial trees of severe NPDR compared to mild/moderate NPDR, Df (a sensitive indicator of change in space-filling patterns) decreased from 1.39 to 1.27. Other parameters of branching complexity, Av, Lv, Br and Nv, decreased by 30%, 51%, and 78% and 74%, respectively. Decreases in parameters for venous density were significant but less marked.
Conclusions: :
In a preliminary study of patients with NPDR, VESGEN mapping and quantification of various complexity parameters for eight or nine vessel branching generations revealed that arterial density decreased more than venous density in the severe NPDR retina, compared to the mild/moderate NPDR retina.
Keywords: retina • blood supply • imaging/image analysis: clinical