You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Nanomedicine for the treatment of retinal and optic nerve diseases. The earliest impact of nanomedicine in ophthalmology is likely to involve the areas of biopharmaceuticals, implantable materials (e.g. tissue regeneration scaffolds, bioresorbable materials), implantable devices (e.g. glaucoma drainage valves), and diagnostic tools (e.g. intraocular pressure (IOP) monitors). Nanotechnology will bring about the development of regenerative medicine (i.e. replacement and improvement of cells, tissues, and organs) and artificial vision. In this chapter, we review ophthalmic applications of nanotechnology in the following areas: drug and trophic factor therapy for glaucoma, retinal degenerative, and retinal vascular disease; gene therapy for retinal degenerative disease; regenerative medicine, including optogenetics and optic nerve regeneration; and diagnostics (minimally invasive IOP monitoring). Nanotechnology will play an important role in both early-stage and late-stage intervention in the management of blinding diseases.
{"Chemical": ["retinal"]}