CT and a echography of optic nerve in glaucoma

Abstract

In 2001, for the first time in its life, the AISG is holding its Annual Meeting far away from its traditional venue, i.e. Rapallo.The explanation for this decision on the part of its Directive Council, approved, moreover, enthusiastically, by the great majority of its members, lies, in my opinion, in two good reasons: 1 the concomitant IGS with the weight of its programme and the number of participants, as well as the outstanding names present; 2 the attractive beauty of this famous city of Prague, so full of history and charming spots.Our idea has been very much appreciated by our Greek colleagues, who have decided to join us in this initiative, which, on the other hand, has been supported right from the beginning as well by the organizers of IGS, Prof Melamed and Prof Schumann. To both of them go our sincere thanks for their welcome and collaboration.Let us think of it this way, however, that a third good reason for joining our forces may lie in the desire not only to exchange ideas and knowledge, but to meet friends who, for many reasons of life, we see all too rarely and with whom it is so nice to spend some time in a pleasant atmosphere speaking of many topics not necessarily only of ophthalmology.Also for this reason, let us succeed in respecting the times of the programme so as to have more time for enjoying ourselves. 7Prague opening remarks Partly as a result of my participation as moderator in the 1999 American Academy of Ophthalmology Glaucoma Subspecialty Day Symposium on Normal Tension Glaucoma, I have been requested to present an overview on this topic. Having made liberal use of materials provided by each of the speakers in the symposium, I wish to thank Drs Brian Lee, David Greenfield and Roger Hitchings and acknowledge their contributions. This presentation will be divided into the following four sections:I. The misnomer of normal tension glaucoma (NTG). II. Potentially contributing factors in the pathogenesis of glaucoma and their relevance to normal tension glaucoma. III. Potentially differentiating characteristics between glaucoma with normal IOP and glaucoma with elevated intraocular pressure (IOP). IV. Lessons learned from the Normal Tension Glaucoma Study. I. The misnomer of normal tension glaucoma (NTG)There is considerable controversy on whether normal tension glaucoma represents a distinct entity or is simply primary openangle glaucoma (POAG) with IOP within the normal range. Because IOP is a continuous variable with no definite dividing line between normal and abnormal, many authorities are questioning whether the term normal tension glaucoma should be abandoned. Normal tension glaucoma is typically defined as a glaucomatous optic neuropathy despite IOP consistently below 21 mmHg. The question must therefore be asked, 'What's so special about 21 mmHg?' Answering that question requires a review of Leydhecker's landmark investigation of 1958 wherein the IOPs of 20 000 eyes were obtained with Schiotz tonometry (Leydhecker et al. 1959). The mean IOP was found to be 15.5 mmHg with a standar...

Fast and Quantitative High-Resolution Magnetic Resonance Imaging of the Optic Nerve at 3.0 Tesla

“…Quantified Diameters of ON and CSF Sheath During Straight Gaze (0°) and 30°A bduction mean values 1,2,4,[13][14][15]17,18,24,25. Diameters between 1.9 mm and 3.5 mm (ON) and between 2.9 mm and 4.4 mm (CSF sheath) can be found in literature, which are similar to the results given in…”

“…Noninvasive diagnosis of the ON sheath by means of ultrasonography has been described in several studies. [1][2][3][4][5][6][7]13,14 However, ultrasonography is known to depend on personal experience and be subjected to interobserver and test-retest variability. Previous studies using MRI techniques for investigation of the ON typically suffered from long acquisition times of between 4 minutes and 15 minutes, 8 -12,15-19 which may lead to artifacts and degradation of spatial resolution caused by the motion of the eyes during the long measurement times.…”

“…1 With age 2 and under certain pathologic conditions, such as intracranial hypertension and papilledema, the diameter of the ON and its CSF sheath may change. 1,[3][4][5][6][7][8][9][10][11][12] Existing diagnostic tools for the assessment of the optic nerve include ultrasonography and magnetic resonance imaging (MRI). Noninvasive diagnosis of the ON sheath by means of ultrasonography has been described in several studies.…”

Retrobulbar Optic Nerve Diameter Measured by High-Speed Magnetic Resonance Imaging as a Biomarker for Axonal Loss in Glaucomatous Optic Atrophy

“…Beatty et al 18 found a mean OND of 2.86 mm in normal and 2.58 mm in glaucomatous eyes using B-scan sonography. Boles Carenini et al 19 applied A-scan sonography and computed tomography in two similar cohorts. Using sonography, they observed an OND of 2.50 mm in normal and 2.28 mm in glaucomatous eyes.…”

Biomarkers and surrogate endpoints in the glaucomatous optic neuropathy: new developments and a review

“…(82) Thinning of the retrobulbar optic nerve has been reported both in histological and diagnostic imaging studies suggesting that the diameter of the nerve may correlate with the extent of the optic atrophy. (83)(84)(85)(86)(87) High-resolution magnetic resonance imaging (MRI) using an ultra fast HASTE-sequence at 3 T sequences of the optic nerve can portray axonal loss in the optic nerve comparing closely with the retinal nerve fiber layer-related parameters and could be used as a biomarker for axonal loss in glaucoma. (82) 3-T diffusion tensor imaging of the optic nerve in patients with glaucoma displays good correlation with the retinal nerve fiber layer thickness measured by OCT and may serve as a biomarker of disease severity.…”