重新认识"正常眼压性青光眼"

Normal tension glaucoma: reconsideration and reevaluation

正常眼压性青光眼(NTG)几乎是青光眼领域里最难以诊断的疾病,难点在于青光眼性视神经病变(GON)的症状和体征缺乏特异性,因此对NTG的重新认识实际上是对GON的重新认识。NTG虽然具有GON的表现,但其发病机制与眼压并无明确的关系,而一些病理因素引起的放射状视盘周围毛细血管网(RPCs)血流异常或轴浆流异常等所导致的视网膜神经节细胞(RGC)损伤则可能是引起GON的真正病因。与GON相关的眼病或全身疾病很多,如高眼压、缺血、缺氧等因素导致的视神经损害以及偏头痛、Flammer综合征(原发性血管调节障碍)、低颅压、低体重指数、低雌激素分泌水平、夜间低血压、睡眠-呼吸暂停综合征、阿尔茨海默病、帕金森病以及基因背景等均可能导致RPCs供血异常或轴浆流障碍,进而出现GON,而部分患者在全身疾病控制后GON也不再进展。就这些患者而言,这些全身疾病并不是NTG的危险因素,而可能是GON的致病原因(或GON是这些疾病的表现之一),因此相应的NTG诊断也要重新考虑。如果在诊断过程中不排除这些病因,仅依据GON、房角开放和正常眼压即诊断为NTG,则容易引起误诊,而完全排除这些疾病再诊断NTG也缺乏临床实际意义。因此,临床实践中重新考虑GON及其所代表的疾病以及NTG的概念、内涵及其诊断标准是必要的。

Normal tension glaucoma(NTG)is almost the most difficult type of glaucoma to diagnose.The difficulty lies in the lack of specificity of the symptoms and signs of glaucomatous optic neuropathy(GON),so the reevaluation of NTG is a new understanding of GON.As a subtype of primary open-angle glaucoma(POAG),NTG is difficult to accurately conceptualize.One of the reasons is that the intraocular pressure(IOP)is closely linked to the occurrence of GON in POAG but not in NTG.GON seems to be secondary to a number of local or systemic disorders,including vascular dysfunction in the optic nerve head induced by compression(elevated IOP)or ischemia,hypoxia,migraine,Flammer syndrome,intracranial hypotension,low body mass index,low estrogen levels,nocturnal hypotension,obstructive sleep apnea-hypopnea syndrome,Alzheimer disease,Parkinson disease,and genetic background,which may influence the flow in the radial peripapillary capillaries(RPCs)and the underfilling of RPCs causing retinal ganglion cell damage.In some cases,GON does not progress with systemic diseases under control,and these systemic diseases are not risk factors for NTG but may be the cause of GON(or GON is one of the manifestations of these diseases).If these causes are not excluded and NTG is diagnosed only on the basis of GON,chamber angle opening,and normal IOP,it is easy to cause misdiagnosis,and the complete exclusion of these diseases is short of clinical significance in practice.In conclusion,the diagnosis of NTG may not be made before the other ocular or systemic disorders capable of presenting with GON are ruled out,and the concept and diagnostic criteria of NTG should be reconsidered.