Mass Dimension Evaluation of the Optic Nerve Head Microvascularity in Non-Glaucomatous Optic Neuropathies

Abstract

In several diseases, fractal analysis has been proven useful to give contribution in diagnosis and prognosis of the patient and to improve treatments. In the present work we have evaluated the mass dimension of the vascular pattern of optic nerve head in non-glaucomatous optic neuropathic patients and healthy controls. Static fluorescein angiogram was performed and the images of the early venous phase were saved. A manual outline of the trajectories of the two-dimensional vascular network was performed down to vessels of 20 micron diameter, processed to threshold the vessel network without background interference and converted into an outline of single pixels and then the fractal analysis was performed. Mass dimension evaluation of the optic nerve head microvascularity was able to differentiate health condition vs. non-glaucomatous neuropathies (p<0.01), as well optic neuritis vs. nonarteritic anterior ischemic optic neuropathy (p<0.01), with high sensitivity and specificity (p<0.0001; p<0.0001). Mass dimension index shows a significantly increased vascular complexity of the optic nerve head in cases compared with controls, also permitting to distinguish between patients affected by optic neuritis vs. nonarteritic anterior ischemic optic neuropathy. This new, fast, unexpensive, methodology may be used in helping the clinician to perform the differential diagnosis between the pathologies and to study the effect of therapies during the follow up of the patient.(NAION) is difficult to be performed on clinical grounds, both giving overlapping clinical profiles [15]. However, it is fundamental to establish an early differential diagnosis, having the ON patient a clear tendency to develop multiple sclerosis, a disease where therapies should be performed as early as possible [16]. In order to verify whether the fractal analysis of the optic nerve head microvascularity could help in the differential diagnosis between ON and NAION, we have evaluated the mass dimension of the optic nerve head vascular pattern, as revealed by fluorescein angiography. SubjectsPatients with unilateral NAION or unilateral idiopathic ON were recruited from the Department of Ophthalmology of the University of Siena. Each patient underwent a complete neuro-ophthalmic examination, including assessment of visual acuity, colour vision, papillary reaction, slit-lamp examination, applanation tonometry, Goldman visual field testing, visual evoked potentials, dilated fundoscopy and fluorescein angiogram.The criteria for patients' admittance with NAION to the study were: unilateral disc swelling with clinical features consistent with NAION [16], no recovery of visual function in the first month of follow up, exclusion of arteritic anterior ischemic optic neuropathy either on clinical grounds or following a negative temporal artery biopsy, negative magnetic resonance imaging of the brain and orbits, no other ocular pathology, no neurological diseases that might influence or explain the patient's visual symptoms. The patient admittance criteria wi...

Multiple sclerosis and eye: Geometric complexity of the optic nerve head microvascularity-a pilot study

“…Our results show that the mean geometric complexity of the microvascular pattern of the optic nerve head is higher in the eye affected by ON than in the eye of control subjects, according to our previous results [16,17]. Moreover, in these MS patients the eye not affected by ON, also, showed a higher geometric complexity of optic nerve head microvascularity than in the normal subjects, overlapping the data of the eye affected by ON.…”