Fractal analysis of fluoroangiographic patterns in anterior ischaemic optic neuropathy and optic neuritis: a pilot study.

Background: To evaluate by means of fractal analysis the vascular pattern of the optic nerve head obtained by fluorescein angiogram, in non-arteritic anterior ischaemic optic neuropathy (NAION) and optic neuritis (ON).

Methods: Twenty-nine patients at the Department of Ophthalmology of the University of Siena, diagnosed as having either NAION or ON by clinical and instrumental criteria, were prospectively subjected to fractal analysis: 11 patients with NAION and 18 patients with ON. In the ON group, 12 patients showed optic disc oedema, whereas six patients showed no optic disc oedema. The unaffected eyes of six patients with NAION and of seven patients with ON associated with optic disc oedema served as controls.

Results: The mean fractal dimension D was 1.84 +/- 0.09 in the NAION group, 1.92 +/- 0.04 in the ON group with optic disc oedema, 1.86 +/- 0.04 in the ON group without optic disc oedema and 1.63 +/- 0.06 in the control group; all case groups showed significantly higher values than controls (P < 0.01). Among the case groups, the ON group with optic disc oedema showed a significantly higher mean fractal dimension value than the others (P < 0.01).

Conclusions: Our data suggest that eyes with ON and NAION seem to have increased vascular complexity in the optic nerve head, manifested as an increase in fractal dimension.