Abstract
Purpose: :
Fractal analysis is a method to quantify the geometric branching complexity and density of the retinal vessels. Vascular disease has been suggested to contribute to pathogenesis of glaucoma, but the degree of this contribution to different glaucoma subtypes is unclear. The aim of this study is to compare retinal vasculature fractal dimension (Df) between eyes with primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG).
Methods: :
This was a clinic study with patients prospectively enrolled from September 2007 to December 2008. Subjects were categorized based on glaucoma subtypes: POAG (high tension glaucoma [HTG] and normal tension glaucoma [NTG]) and PACG. Retinal photographs were taken from all the participants. Df was measured following a standardized protocol by a trained grader with the International Retinal Imaging Software-Fractal program (IRIS-Fractal).
Results: :
A total of 517 glaucoma subjects (314 males and 203 females) were recruited for analysis. The majority of the subjects were Chinese (90%). There were 351 subjects with POAG (178 with HTG, 173 with NTG) and 166 subjects with PACG. After adjusting for age and gender, mean Df in PACG was significantly lower in POAG (1.396 (SD 0.004) vs 1.416 (SD 0.003), p<0.001). Within the POAG group, mean Df was significantly lower in HTG compared with NTG (1.410 (SD 0.004) vs 1.421 (SD 0.004), p=0.001).
Conclusions: :
Eyes with PACG had lower retinal Df than eyes with POAG. This difference in retinal microvascular complexity and density may reflect different underlying contribution of vascular mechanisms between glaucoma subtypes.
Keywords: imaging/image analysis: clinical • optic flow • pathobiology