Investigation on the distinct electroretinogram in dogs with different cataract stage and ocular disease

視網膜電圖是一項非侵入性且能評估視網膜功能的檢查，常應用於診斷視網膜發育障礙及白內障手術前對視網膜功能的評估。視網膜電圖是偵測在光線刺激後視網膜所產生的電流反應，而以波型的方式來呈現。光線刺激後首先產生一個往下的a波，緊接著地是一個往上的b波。a波及b波的絕對時間及振幅等參數為記錄要點。許多品種因遺傳因素同時好發白內障與進行性視網膜萎縮，而視網膜退化在眼底的症狀僅能在白內障未遮蔽眼底影像時才能見到。因此，在混濁的媒介存在下，無法見到眼底又想確定視網膜功能時會借助視網膜電圖來偵測其改變。白內障手術前先以視網膜電圖檢查視網膜功能是必要的，因為在視網膜失去功能的情況下，移除混濁的水晶體也無法使病犬恢復視力，當然就失去施行白內障手術的必要性了。近年來，視網膜電圖檢查已經廣泛地應用於白內障手術前評估視網膜功能，然而，在不同分期白內障及其他眼科疾病對視網膜電圖造成的影響僅有少數研究提及。因此，本研究的目的在研究不同分期的白內障及其他眼科疾病如水晶體性葡萄膜炎、角膜疾病等等對視網膜電圖造成的影響。研究中所使用的視網膜電圖檢查流程是參考Narfstrom等人在2002年發表的犬視網膜電圖準則裡的short protocol，使用的鎮定劑為Zoletil。而研究中所提及之正常犬視網膜電圖結果是根據先前本實驗室所建立之正常參考值而來。研究中比較不同年齡白內障犬之視網膜電圖參數，顯示當年紀愈老，a波及b波振幅便會較低，且其關聯性達顯著。當比較不同性別白內障犬之視網膜電圖參數，結果並無顯著差異。當比較不同分期白內障犬與正常犬之視網膜電圖參數，顯示於暗適應5分鐘後，成熟期白內障犬其b波平均振幅相較於正常犬，有顯著變小的情形 (P0.05)。當比較角膜色素沉著之犬隻與正常犬之視網膜電圖參數，顯示當角膜沉著的範圍愈大，b波振幅便會較低，且其關聯性達顯著。視網膜電圖是白內障術前重要的檢測項目，其優點在於當混濁的白內障阻擋眼底檢查時，可以利用視網膜電圖來評估視網膜功能。但有許多相關因素會影響其結果，而可能誤判為視網膜功能受損。因此，本研究結果建議判讀視網膜電圖時需要同時考慮年齡、白內障分期及角膜疾病等等的因素。正確地判讀視網膜電圖，才可以有效評估白內障手術執行之必要性及預估術後視力恢復的能力。Electroretinogram (ERG) recording is a valuable noninvasive tool in the evaluation of retinal function. ERG is mainly utilized for the early diagnosis of progressive retinal atrophy (PRA) and pre-operative evaluation of retinal function in canine cataract patients by recognition of the amplitude and implicit time of a-wave and b-wave. Many breeds are genetically predisposed to both cataracts and PRA. Funduscopic signs of retinal degeneration cannot be visible in dogs with mature cataract formation. ERG is a potential which arises in the retina after light stimulating and can be used to assess the retinal function in the presence of an opaque medium like cataract. ERG is an indispensable procedure to assess retinal function and to eliminate cataract patients with retinal degeneration before cataract surgery, in order to restore vision postoperatively. In recent years, ERG is extensively utilized for the pre-operative evaluation of retinal function in canine cataract patients. Nevertheless, there are barely few research mention that the effects of cataract and other ocular disease on ERG in dogs. Therefore, the goal of our study was to investigate the effects of different stage of cataract and other ocular disease (such as lens-induced uveitis and corneal disease) on the consequence of ERG. The short ERG protocol was used and cooperated with Zoletil, functioning as the tranquilizer. Data of normal dogs quoted from previous study, which previously conducted in our lab was used as reference data. Results: Senile cataract dogs exhibited greater extent of a decreasing a- and b-wave amplitude than adult cataract dogs. There was significant difference on ERG results in different age of cataract dogs, while no significant ERG difference in different gender. As compared the ERG data between different cataract stage of dogs and normal dogs (reference data), dogs with mature cataract displayed that significant decline of b-wave amplitude after dark adaption for 5 minutes (P