Image analysis of optic nerve disease

Abstract

Existing methodologies for imaging the optic nerve head surface topography and measuring the retinal nerve fibre layer thickness include confocal scanning laser ophthalmoscopy (Heidelberg retinal tomograph), optical coherence tomography, and scanning laser polarimetry. For cross-sectional screening of patient populations, all three approaches have achieved sensitivities and specificities within the 60-80th percentile in various studies, with occasional specificities greater than 90% in select populations. Nevertheless, these methods are not likely to provide useful assistance for the experienced examiner at their present level of performance. For longitudinal change detection in individual patients, strategies for clinically specific change detection have been rigorously evaluated for confocal scanning laser tomography only. While these initial studies are encouraging, applying these algorithms in larger numbers of patients is now necessary. Future directions for these technologies are likely to include ultrahigh resolution optical coherence tomography, the use of neural network/machine learning classifiers to improve clinical decision-making, and the ability to evaluate the susceptibility of individual optic nerve heads to potential damage from a given level of intraocular pressure or systemic blood pressure. Definition of termsThere are at present two principal tasks for these imaging systems. First, cross-sectional screening, in which an eye is imaged initially with the intention of detecting the presence of glaucomatous optic nerve damage. Second, longitudinal change detection, in which an eye that is already known to be at risk is imaged on multiple occasions over time with the intention of detecting change or progressive damage. Current instruments Heidelberg retinal tomographThe Heidelberg retinal tomograph (HRT) is a confocal scanning laser ophthalmoscope (CSLO) that uses a 670 nm diode laser to obtain a series of two-dimensional optical section images of the ONH and peripapillary retina. A threedimensional topographic image of the ONH surface is then built from the series of 16-64 serial optical sections, when algorithms are used to find the surface at each of 256 Â 256 (HRT I) or 384 Â 384 (HRT II) pixels over a 10 or 151 field of view. The HRT II automatically captures three consecutive 151 images and from these generates a mean topographic image.To process images, the optic disc margin (anterior scleral canal opening) is defined by a contour line placed around the inner margin of the peripapillary scleral ring. The standard reference plane for volumetric parameter calculation is then automatically determined as 50 mm posterior to the mean peripapillary retinal height along the contour line between 350 and 3561; however, the reference plane

The Correlation Between Visual Field Defects and Focal Nerve Fiber Layer Thickness Measured With Optical Coherence Tomography in the Evaluation of Glaucoma

“…Unfortunately, the RNFL is not the only birefringent structure in the eye, and it remains unclear what the effects of corneal and lenticular birefringence aging are on polarimetric measurements. [13][14][15][16] OCT evaluates the reflectance of posterior segment structures and incorporates a mathematical algorithm capable of localizing the anterior and posterior limits of the RNFL. The procedure enables cross-sectional visualization and direct measurement of RNFL thickness with low coherence light, which is applied through a noncontact, noninvasive instrument, and depicts the retinal microstructure with a resolution of 10 mm.…”

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

“…To facilitate early diagnosis, researchers have focused on objective morphological analysis of the retrobulbar tract and the head of the optic nerve, in order to reduce the bias caused by subjective medical interpretations [20]. Optic nerve analysis by means of magnetic resonance imaging, digital stereoscopy and Heidelberg retina tomography are some examples of how recent technologies can quantitatively document peculiar clinical findings in ON, NAION and other optic nerve diseases [21][22][23].…”

The Topography of the Optic Disc in Diabetic Patients

“…The quantification of the ONH (topographic parameters) has been utilized primarily in the evaluation of glaucoma; and reports of HRT usage in non-glaucomatous optic nerve diseases are still quite limited [8,9] . However, there are only a few reports regarding changes in RNFL and ONH structures in diabetic patients by using HRT [14,15] .…”

“…In addition, it has some advantages such as obtaining rapid imaging without pupil dilatation, imaging in blurred media and high repeatability. The HRT analysis simply yields more information and more parameters [8][9][10][11][12][13] . In this study, topographic features of the ONH in diabetic eyes were investigated with HRT III.…”

“…The optic nerve head (ONH) and the peripapillary retinal nerve fiber layer (RNFL) can be evaluated by using confocal scanning laser systems. Heidelberg retinal tomography (HRT) is one of these systems and has become widely used [3][4][5][6][7][8][9] . Structural features of the ONH are well known to predispose to a number of ocular diseases such as nonarteritic ischemic optic neuropathy (NAION) [10][11][12] .…”