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

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. Subjects Patients 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 with ON for the present research were: unilateral visual impairment associated with impaired colour vision and visual-field loss, presence Introduction Fractal analysis is a very useful tool in the understanding of many phenomena in various fields, such as astrophysics, economics, biology and medicine. Interesting results have also been achieved in bacteriology, medical imaging and ophthalmology (e.g. diabetic retinopathy) [1-6]. Retinal vascular network in healthy subjects has a value of fractal dimension [7], close to the value of a Diffusion-Limited Aggregation (DLA) process (D≈1.70) [8], while in pathologic condition that value changes deeply. We can recall papers by Cavallari et al. [9], that showed a reduction in complexity of retinal vessels, reflecting the alteration of the brain microvessels in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL ) and the ones by Doubal et al. [10], that found a low value of retinal vessels fractal dimension associated to the lacunar stroke and by Ţalu et al. that, recently, showed that fractal analysis is able to characterize the human non-proliferative diabetic retinopathy [11]. In these works, fractal analysis has been demonstrated a sensitive tool to assess changes of retinal vessel branching, able to reflect the early microvessel alterations in human pathology. Moreover, the retina vessels network, described by generalized dimensions and singularity spectrum, has a multifractal structure (an object having different fractal properties in its different region) [12]. These multifractal approaches were able to characterize the retinal vascular architecture disorder in several diseases [11,13,14]. At initial presentation, the differential diagnosis between optic neuritis (ON) and nonarteritic anterior ischemic optic neuropathy Research Article Mass Dimension Evaluation of the Optic Nerve Head Microvascularity in Non-Glaucomatous Optic Neuropathies Giorgio Bianciardi1*, Maria Eugenia Latronico2 and Claudio Traversi2 1Department of Medical Biotechnologies, University of Siena, Siena, Italy 2Department of Medical Sciences, Surgery and Neurosciences, University of Siena, Siena, Italy Dates: Received: 30 January, 2016; Accepted: 03 March, 2016; Published: 07 March, 2016 *Corresponding author: Bianciardi Giorgio, MS, MD, PhD, Department of Medical Biotechnologies, University of Siena, Siena, Italy, E-mail: www.peertechz.com ISSN: 2455-4634