The Beaver Dam Eye Study and Blue Mountains Eye Study, which have similar methodologies, reported an overall disc hemorrhage prevalence of 0.9% and 1.4%, respectively. Several population-based studies have reported disc hemorrhage prevalence estimates ranging from 0.6% to 1.4%. The fact that disc hemorrhages occur at or near preexisting rim notches lends evidence to the theory that glaucomatous damage begins prior to the appearance of a hemorrhage. Their observations that a rim notch may precede disc hemorrhage (on average, by 21.5 months) and that disc hemorrhages occurred at or adjacent to rim notches differed from older work that suggested disc hemorrhages precede notches. In a study of 33 eyes for which optic disc images prior to development of a disc hemorrhage were available for review, Law and colleagues noted that all eyes with preexisting neural rim notches had a subsequent disc hemorrhage at or adjacent to the notches. Several studies have noted a positive association between rim notching and ODH. The Relationship to Rim NotchesĪ neural rim notch is a localized divot in the neuroretinal rim. The relationship between pathogenesis and ODH location, shape, and retinal depth is an ongoing area of research. Given the presence of disc hemorrhages in glaucomatous and non-glaucomatous eyes, it is probable that multiple factors may contribute to their development. The etiology of optic disc hemorrhages remains an area of active research. Further, densitometric studies have suggested that the blood from ODHs may have an arterial origin. Recent use of OCT angiography has shown that 46.3% of eyes with disc hemorrhages show peripapillary choroidal microvascular dropout at the site of hemorrhage, as compared to 29.4% of eyes without hemorrhage. In this theory, a yet unknown primary vascular problem increases vessel susceptibility to damage and rupture. Other authors suggest various vascular etiologies, for example, ischemic microinfarction in the optic nerve head or perturbation of the blood-retinal barrier. The hemorrhage is a secondary event resulting from tissue damage. Essentially, this theory suggests that the primary insult is neurodegenerative, causing changes or stretching of connective tissue, remodeling of lamina cribosa, and/or traction from glial scar formation, which in turn damages the microvascular network leading to hemorrhage. Proponents of the mechanical theory hypothesize that disc hemorrhages result from mechanical shearing at the lamina cribrosa or damage to the capillary network at the border of retinal nerve fiber layer defect enlargement. Two primary hypotheses exist: mechanical and ischemic vascular. Etiology and Pathophysiology Mechanical and Vascular HypothesesĪlthough disc hemorrhages have been the subject of tremendous research, the exact mechanism by which they appear remains elusive. ![]() Less commonly, a disc hemorrhage may be noted in the peripapillary retinal nerve fiber layer reaching within one disc diameter of the optic disc margin. Alternately, deeper disc hemorrhages may appear round and blotchy. Classically, these hemorrhages are located in the prelaminar optic disc, cross the peripapillary zone, and extend into the adjacent superficial retinal nerve fiber layer, although they may not occupy the entire length from disc to retina. 9.2.2 Recurrent Disc Hemorrhages: The two-population hypothesisĪlternate names: optic disc hemorrhage, Drance hemorrhage, splinter hemorrhage, nerve fiber layer hemorrhage, optic nerve head hemorrhage.ĭisc hemorrhages are splinter or flame-shaped hemorrhages oriented perpendicular to the optic disc margin ( Figure 1).9.1.1 Do all individuals with disc hemorrhage develop glaucoma?. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |