The human sclera accounts for 95% of the surface of the eyeball, providing ample contact area which is suitable for targeted trans-scleral ocular drug delivery. Currently there are several tans-scleral sustained-release strategies, including intra-scleral delivery, episcleral delivery, as well as tans-scleral iontophoresis. Different devices and methods have their own advantages and disadvantages, for example, intra-scleral delivery is somehow invasive, and episcleral delivery device needs to be made thin to prevent erosion of conjunctiva, iontophoresis needs to be frequently repeated as of its short-term effect. With the development of bio-material engineering technology, episcleral microfilm could become an ideal drug delivery route for posterior segment ocular diseases.