青光眼视神经损害的三要素及其盘沿丢失的识别

诊断青光眼视神经损害的三要素为盘沿丢失、视网膜神经纤维层缺损（RNFLD）及视盘线状出血。三要素中如有两要素改变应诊断为视神经损害。对于盘沿丢失已往的教科书中均无明确描述,笔者认为识别盘沿丢失必须首先认识正常盘沿形态及其影响因素。大多数的正常盘沿形态符合ISNT法则,生理性大视杯也符合该法则。不符合ISNT法则者为盘沿丢失,或者为正常盘沿形态变异。后者如部分小视盘下方盘沿可比上方盘沿窄,判断是否上、下方盘沿丢失时应将其与鼻侧盘沿进行比较;横椭圆视盘鼻侧盘沿较宽,应上、下盘沿比较;视盘主干血管发出位置偏位、视盘倾斜也会影响盘沿形态。如果参照ISNT法则认识正常盘沿变异因素,就不难发现盘沿丢失。然而不是所有的盘沿丢失均为青光眼所致,应鉴别非青光眼性视神经损害。

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

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.