銀杏葉萃取物用於預防紫外線B所引起的角膜病理問題與視覺衰退之探討

紫外線B (UVB) 輻射是造成眼球表面產生病理問題的主要風險因素，包括光害性角膜炎、角膜混濁及角膜發炎症反應。長期曝曬於UVB輻射下會使眼睛產生氧化壓力，可能與角膜病理的複雜性發展有關。圓錐角膜 (Keratoconus; KC) 是一種角膜錐形退化的疾病。研究發現在KC角膜上有氧化壓力的表現，推測氧化壓力的累積可能與KC的病理發展有關。因此，氧化壓力的表現可作為一個新指標，用以發展預防策略或治療指標的參考。然而，角膜錐形退化 (Cone-shaped degeneration) 的發展是否與UVB輻射有關，目前尚未有直接的證據。本實驗首先採取角膜地圖影像 (Corneal topography image) 與裂隙影像 (Slit lamp image) 分析系統，探討UVB輻射是否可以誘導小鼠產生角膜錐形退化發展的問題。同時，本實驗採取此模式用以探討銀杏葉萃取物 (Ginkgo biloba leaf extracts; GK) 是否具有預防UVB引起的角膜錐形退化或其他複雜性的角膜問題，並評估其減緩視覺衰退的保護效果。本研究採取角膜地圖影像分析、裂隙影像分析、視覺敏感度 (Visual acuity; VA) 分析與組織病理分析進行實驗探討。結果發現，UVB在 0.72 J/cm2 的強度下，從裂隙影像可觀察到角膜錐形退化的發展，UVB曝曬期間給予GK 1 mg/kg 及 5 mg/kg 處理的組別，可以降低此角膜錐形退化問題的進展。此外，GK有視覺保護的效果，且給予GK 1 mg/kg 及 5 mg/kg 的組別比UVB與給予GK 0.2 mg/kg的組別，有更好的視覺保護效果。整體而言，銀杏葉萃取物具有潛力在未來開發成預防性眼睛表面用藥，避免UVB造成角膜錐形病理變化。

Ultraviolet-B irradiation is a major risk factor for the pathogenesis of ocular surface disease, including photokeratitis, corneal opacity, and corneal inflammation. Chronic exposure to UVB irradiation can causes oxidative stress on cornea, which might be involved in the process of complexities corneal pathology. Keratoconus (KC) is the cone-shape degeneration of the cornea. The increased levels of oxidative stress markers were found in KC corneas indicate that oxidative stress might be involved in the progression of this disease, and that may provide new insights for its prevention and treatment in the future. However, there were no studies investigating whether UVB can induce the progression of corneal cone-shaped degeneration. In this study, we first examined whether the cone-shape corneal topography and cone-shape slit lamp image of the mouse in vivo can induced by UVB irradiation. In addition, we also investigate the preventive effects of the ginkgo biloba leaf extracts (GK) on UVB-induced corneal cone-shaped degeneration, and other complexities of corneal pathologic changes and even the declining of vision. The evaluation of corneal topography image, slit lamp image, visual acuity assessment and histological analysis were conducted in this study. The results indicated that daily UVB irradiation at 0.72J/cm2 level could initiate the progression of cone-shaped corneal disorder, indicated by cone-shape slit lamp image from mouse cornea, and these pathologic changes could be attenuated by GK administration at the dosage of 1 mg/kg and 5 mg/kg during UVB irradiation exposure. In addition the GK 1 mg/kg and 5 mg/kg administration group obtained better preventive effects than the 0.2 mg/kg and UVB treated alone groups on visual acuity. Overall, GK has the potential to develop a prophylactic agent for the surface of the eye, preventing the disorders of cone-shape pathologic changes in cornea induced by UVB irradiation.