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標題: | 斜弱視的神經機制與臨床研究 Neural mechanisms and clinical research of strabismus and amblyopia |
作者: | Tzu-Hsun Tsai 蔡紫薰 |
指導教授: | 胡芳蓉(Fung-Rong Hu) |
關鍵字: | 弱視,斜視,先天性白內障,抑制,擴散頻譜造影, amblyopia,strabismus,congenital cataract,suppression,diffusion spectrum imaging, |
出版年 : | 2018 |
學位: | 博士 |
摘要: | 弱視是是兒童常見的眼疾,不僅是造成孩童單眼視覺缺損的一個重要原因,也是成人單側永久視覺喪失的最常見的疾病之一。弱視發生的原因是在視覺發育關鍵期間,兩眼或是單眼的視覺訊息沒有辦法清晰的傳導到視皮質,使得視皮質上對應的神經無法正常發育,造成視力無法矯正到萬國視力表壹點零或是兩眼矯正視力差別達兩行以上。弱視的原因包括1. 屈調異常,(例如高度遠視、近視與散光)、2. 斜視、3. 兩眼不等視以及4. 剝奪性因素(例如先天性白內障、眼瞼下垂等)。
在本論文中,我們針對臨床常見的弱視相關疾病,探討其背後的神經機轉以及診斷治療方法的改良。研究的疾病包括斜視(神經性病變斜視與間歇性外斜視)、不等視及斜視性弱視、以及先天性白內障。研究方法將以磁振造影、心理物理學實驗以及臨床研究,了解: 1. 弱視與斜視病患的神經結構及腦部白質神經纖維束的變化; 2. 間歇性外斜視中雙眼抑制的啟動機制;3. 臨床上先天性白內障手術的改良方法。 首先,我們將利用磁振造影技術來分析神經性病變斜視的原因。在臨床上尋找神經性病變斜視的病因不易,往往做了許多影像檢查以及血清檢驗仍無法得知致病原因。一些臨床神經病變症候群已被證實是腦部異常血管神經壓迫造成的,我們因此假設血管神經的壓迫也會造成斜視;利用重T2 加權高解析度磁振造影,加上運用穩定態取像之快速造影進行腦幹顱神經造影,分析36 位顱神經麻痺造成的神經性病變斜視,結果發現其中十位被傳統檢查歸類於不明原因的斜視患者,30%其實有血管神經的壓迫,並有眼外肌萎縮的證據。 針對弱視患者的腦部白質神經纖維束變化,則蒐集了十位弱視患者以及二十位控制組,以擴散頻譜造影合併全腦神經纖維追蹤術自動分析掃描腦部,再以群組分析之無閥值集群加權分數比較,發現弱視患者有9 條白質神經纖維束之11 個節段中的綜合非等向性指標較正常人降低。這些神經纖維束變化可能與弱視相關的一些功能變異,例如視覺處理、視聽覺整合及手眼協調等有關。 斜視的雙眼間抑制現象是斜視患者腦部特別的神經機轉,可以避免因眼位不正所產生的複視;不過抑制的出現也會讓雙眼的融像能力減弱,使斜視頻率增加。第三部分中以心理物理學實驗的方法,以電腦程式模擬同視機的機制,研究間歇性外斜視的患者抑制啟動的機制。在這個研究中,發現外斜視患者雙眼間的抑制,是由於雙眼視網膜上相對應點的影像訊息不一致所引發,而不是眼外肌偏斜時產生的運動訊號啟動。這個發現可以運用在臨床上協助間歇性外斜視的初期控制。 最後一部分是研究先天性白內障患者手術方法的改良,先天性白內障手術有很高的比例會伴隨後囊增生混濁的併發症,我們假設以triamcinolone acetonide 針對玻璃體染色,可以改善玻璃體切除術的完成度。分析了三十四位病患五十一隻眼睛的臨床資料,發現這樣的手術方式可使後囊增生混濁率減少到5.9%;此併發症發生的最大危險因子是在一歲以下接受手術。到追蹤期間結束為止,有百分之七十的病患術後視力優於0.3 logMAR,43.3%比0.1 logMAR 為佳。 這些針對弱視相關眼疾的研究,目的在於能更了解斜弱視的神經機制,並利用研究結果運用在臨床上的診斷、控制與治療。 Amblyopia is a neurodevelopmental disorder of the visual cortex that occurs when binocular vision is disrupted during early childhood. Common causes of amblyopia include refraction error, anisometropia, strabismus, and visual deprivation arising from ptosis or congenital cataract. In order of understanding the mechanism and treatment strategies in amblyopia-related diseases, we used neuroimaging tool (high resolution MRI and diffusion spectrum imaging (DSI)), psychophysics study and clinical research to investigate different aspects of amblyopia. In the first part of the study, we prospectively use high resolution MRI and the heavily T2-weighted fast imaging employing steady-state acquisition (FIESTA) sequence to investigate the neurovascular relationship in patients with idiopathic neuropathic strabismus. We hypothesized that if CN III, CN IV, or CN VI were compressed by dolichoectatic vessels, associated ocular motility would be hindered and subsequent denervation atrophy of the involved extraocular muscle atrophy would be expected to develop. The results showed that ten (28%) of the 36 total patients who underwent high-resolution MRI in the study who had CN VI or CN III palsies were considered idiopathic. 30% of them had neurovascular compression as well as evidence of denervation extraocular muscle atrophy. In the second part of study, we investigated the microstructural changes in the white matter of adults with amblyopia using DSI with systematic tractography-based automatic analysis (TBAA) of the whole brain. 10 adults with amblyopia and 20 age and sex-matched normal-sighted controls were enrolled. The mean generalized fractional anisotropy (GFA) was measured in 76 white matter tracts and compared between the experimental and control groups using a threshold-free cluster-weighted (TFCW) method and t-test. Participants with amblyopia had significantly lower GFA values than the controls in 11 segments located in 9 white matter tracts, which may be associated with various higher-level deficits such as audiovisual integration and hand-eye coordination. Suppression has been proposed as the neuromechanism that prevents binocular diplopia in strabismic patients. In this part of study, we designed a computer program to simulate the function of a troposcope by continuously projecting half of a stereograph onto both foveae during the exotropic phase in intermittent exotropia (X(T)) participants. Our results demonstrated that binocular vision could remain intact until nearly the maximum exotropic phase in subjects with X(T). We determined that the antidiplopic mechanism in human X(T) is evoked by different images projected onto the corresponding retinas (sensory signal) rather than by motor signal of the extraocular muscle deviation. In the final part of study, we evaluated the outcomes of cataract surgery with triamcinolone-assisted vitrectomy in patients younger than 72 months of age. Satisfactory outcomes were achieved, including improved postoperative visual acuity, a low complication rate with a high proportion of in-the-bag intraocular lens implantation, and intact pupillary configuration. Staining with triamcinolone acetonide facilitates identification of vitreous strands in pediatric cataract surgery without serious long-term adverse effects. The anti-inflammatory effect of triamcinolone acetonide might play a role in the prevention of postoperative visual axis obscuration. Although the incidence of visual axis obscuration is low, it remains unavoidable in approximately one-sixth of patients who undergo this surgical technique before 12 months of age. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20189 |
DOI: | 10.6342/NTU201800072 |
全文授權: | 未授權 |
顯示於系所單位: | 臨床醫學研究所 |
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