Fractal dimension as a new tool to analyze optic nerve head vasculature in primary open angle glaucoma

Aim: To investigate the features of optic nerve head (ONH) microvasculature in primary open angle glaucoma using fractal geometry analysis. Patients and Method: ONH blood flow was analyzed at the level of the lamina cribrosa by means of confocal scanning laser Heidelberg Doppler flowmetry (HRF) in medically-controlled early and advanced glaucoma. Fractal dimension D of vasculature map was calculated using the Box Counting. Results: Our data demonstrated that, in patients with advanced glaucoma, fractal dimension D was significantly lower than in controls, whereas, in the early stage of disease, its value was similar. Fractal dimension D of microcirculation was significantly and negatively correlated with the cup-disk area ratio in both early and advanced glaucoma groups, whereas linear cup-disk ratio of the disk, cup shape measure and nerve fiber layer thickness, where correlated only in advanced stage of the disease. Conclusion: These findings demonstrate that fractal dimension D of ONH appeared significantly reduced in advanced glaucoma and correlated with the optic disc damage.