Three essential elements of glaucomatous optic nerve damage and discrimination of optic nerve rim loss

Abstract

Three essential elements of glaucomatous optic nerve damages are optic nerve rim loss, retinal nerve fiber layer defects (RNFLD) and optic disc linear hemorrhages. It's suggested that if there are two positive signs detected among the three elements, the diagnosis of the glaucomatous optic nerve damages can be established. There is no definitely described how to identify optic nerve rim loss in the previous textbooks, therefore it is important to know about the morphological features of the physical optic nerve rim and influence factors before discrimination of optic nerve rim loss. Most of physical optic nerve rim are in accordance with ISNT rule, physical large optic cups are also accord with ISNT rule. Exceptional cases exist in two patterns, optic nerve rim loss or normal optic nerve rim morphological variances. The latter includes part of small discs, horizontally oval optic discs, the position of the central retinal vessel trunk and the titled optic discs which affect the morphological feature of optic nerve rim as well. In some small discs, the width of inferior rim is narrower than that of superior rim, therefore, the inferior or the superior rim loss can be evaluated by comparison with nasal rim width. Concerning horizontal oval optic discs, the width of inferior rim and superior rim should be compared to evaluate whether there is the optic nerve rim loss. If those patterns of normal optic nerve rim variances can be recognized, it is not difficult to find the presence of the optic nerve rim loss. However, not all of the optic nerve rim loss is due to glaucomatous optic nerve damages, non-glaucomatous optic nerve damage should be distinguished.