視網膜電圖(Electroretinogram, ERG)是光線刺激視網膜後所產生電流反應的記錄。藉由計算視網膜電圖中a波與b波的振幅(amplitude)與絕對時間(implicit time)之關係,可用來評估視網膜的功能。其主要運用於進行性視網膜萎縮(Progressive retinal atrophy, PRA)的早期診斷以及白內障病犬視網膜功能的術前評估。在獸醫,因為與動物溝通之障礙,因此客觀的評估視網膜功能是不可行的。許多的研究已經證實視網膜電圖是一種能夠有效率且客觀的評估視網膜功能的方法。視網膜電圖記錄的是非常微小的電流反應,約0.000001伏特。任何微小的移動都可能造成測量上的誤差,因此動物在進行視網膜電圖時,都必須麻醉。然而,許多科學家發現不同的麻醉方式會造成不同視網膜電圖的結果。Isoflurane以及medetomidine是多年來進行視網膜電圖常使用的麻醉藥物。Zoletil則是一種注射式麻醉、鎮靜劑,由類似ketamine與diazepam的兩種藥物混合而成,具有迅速誘導麻醉及甦醒恢復時間短的特性,近年來經常使用於鎮靜以及短時間的手術。本研究的目的是在於比較Zoletil、medetomidine以及isoflurane在short ERG protocol中對視網膜電圖的影響;並同時檢視Zoletil是否適合用於視網膜電圖的檢查。實驗對象為六隻健康的混種犬。每隻犬皆分別使用Zoletil和medetomidine鎮靜以及使用isoflurane全身麻醉,之後進行相同流程的視網膜電圖檢查。使用Zoletil與medetomidine鎮靜的組別於暗適應下b波的振幅有顯著差異,以Zoletil組較大。而比較鎮靜與全身麻醉的視網膜電圖,可以發現當麻醉時,暗適應下a波和b波的振幅皆顯著的變小,但是絕對時間則沒有明顯改變。不同麻醉劑造成不同視網膜電圖結果的原因,可能與麻醉劑影響視網膜內的神經傳導物質(neurotransmitter)有關。在檢視視網膜電圖的結果時,使用的麻醉方式必須要列入考量。本試驗顯示以Zoletil鎮靜能夠獲得良好的視網膜電圖結果,可做為進行視網膜電圖時的另一個選擇。 基於前敘的實驗結果,我們進一步以Zoletil對41隻正常犬進行視網膜電圖探討的研究,其過程使用short ERG protocol。在本實驗中得到的正常參考值為:在暗適應下,a波的振幅為11~99 μV,絕對時間為12~16.5 ms;b波的振幅及絕對時間為77~237 μV 及28.9~52.8 ms。雙眼a、b波的振幅及絕對時間皆十分接近,顯示對稱性良好。在不同年齡層的比較上,幼犬、成犬與老犬的視網膜電圖並沒有顯著差異。而在暗適應下,b波的振幅在公犬有顯著大於母犬的情形。另外針對18隻罹患眼科疾病病犬進行視網膜電圖檢查,發現罹患眼科疾病犬隻的b波振幅稍低於正常值。本研究的結果與之前的文獻略有不同,可能的相關原因於文中探討。 中文摘要…………………………………………………………...…………………..i 英文摘要……………………………………………………….……………………..iii 目次……………………………………………………………………...…………….v 圖次…………………………………………………………………....…………….viii 表次………………………………………………………………………………..….ix 第一章 緒言……………………………………………………………………........1 第二章 文獻探討…………………………………………………............................3 第一節 犬視網膜的解剖構造與生理功能……………………………………..3 1-1 光受器………………………………………………………………….....4 1-2 視覺的神經傳導路徑…………………………………………………….5 第二節 視網膜電圖……………………………………………………………..5 2-1 視網膜電圖的歷史……………………………………………………….6 2-2 視網膜電圖的原理……………………………………………………….8 2-3 犬視網膜電位圖的protocol類型………………………………………..8 2-4 犬視網膜電圖的判讀…………………………………………………...10 第三節 視網膜電圖在獸醫之臨床應用………………………………………11 3-1 白內障…………………………………………………………………...12 3-2 進行性視網膜萎縮……………………………………………………...12 3-3 突發性視網膜退化症…………………………………………………...15 3-4 視網膜毒性評估………………………………………………………...15 第四節 影響視網膜電圖之因子………………………………………………16 4-1 儀器因子………………………………………………………………...16 4-2 動物因子………………………………………………………………...17 第五節 不同麻醉方式對視網膜電圖之影響…………………………………18 5-1 全身麻醉與鎮靜對視網膜電圖的影響………………………………...19 5-2 不同麻醉方式對犬視網膜電圖之影響……………………………...…20 5-3 不同麻醉方式對其他動物視網膜電圖之影響………………………...22 第三章 材料與方法………………………………………………………………....24 第一節 材料…………………………………………………………………....24 1-1 實驗動物……………………………………………………………...…24 1-2 藥品……………………………………………………………………...24 1-3 器材與耗材……………………………………………………………...25 第二節 方法……………………………………………………………………27 2-1 建立基本資料…………………………………………………………...27 2-2 眼科學檢查……………………………………………………………...27 2-3 實驗流程………………………………………………………………...28 第三節 分析與統計……………………………………………………………33 第四章 結果…………………………………………………………………………34 第一節 視網膜電圖之波形變化………………………………………………34 第二節 不同鎮靜劑下視網膜電圖之比較……………………………………35 2-1 Zoletil與medetomidine鎮靜下波形的差異…………………………..35 2-2 a波平均振幅的差異…………………………………………………..35 2-3 a波平均絕對時間的差異……………………………………………..35 2-4 b波平均振幅的差異…………………………………………………..37 2-5 b波平均絕對時間的差異……………………………………………..37 第三節 全身麻醉與鎮靜下視網膜電圖之比較………………………………39 3-1 Zoletil鎮靜與isoflurane全身麻醉下波形的差異……………………39 3-2 a波平均振幅的差異…………………………………………………..40 3-3 a波平均絕對時間的差異……………………………………………..40 3-4 b波平均振幅的差異…………………………………………………..41 3-5 b波平均絕對時間的差異……………………………………………..41 第四節 三種麻醉藥物之綜合比較…………………………………...……….43 第五節 正常犬視網膜電圖之研究……………………………………………44 5-1 正常參考值…………………………………………….………………..44 5-2 雙眼對稱性…………………………………………….………………..45 5-3 不同年齡層之差異…………………………………….………………..46 5-4 不同性別之差異……………………………………….………………..47 第六節 眼科疾病犬與正常犬之比較…………………………………………48 6-1 白內障犬與正常犬之比較……………………………………...………48 6-2 角膜疾病犬與正常犬之比較……………………...……………………48 6-3 失明犬及眼球脫出犬與正常犬波形之差異……………………..…….50 第五章 討論…………………………………………………………………………51 參考文獻……………………………………………………………………………..59 參考文獻 Books: Branson KR, Booth NH. 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Electronic Resources: 1. instruct.uwo.ca/anatomy/530/350notes.htm 2. webvision.med.utah.edu/ClinicalERG.html