Nanotechnology involves the creation and use of materials and devices at the size scale of intracellular structures and molecules, and involves systems and constructs in the order of <100 nm. The aim of nanomedicine is the comprehensive monitoring, control, construction, repair, defence, and improvement of human biological systems at the molecular level, using engineered nanodevices and nanostructures that operate massively in parallel at the single-cell level, ultimately to achieve medical benefit. In this review we consider general principles of nanotechnology as applied to nanomedicine (e.g., biomimicry and pseudointelligence). Some applications of nanotechnology to ophthalmology are described (including treatment of oxidative stress; measurement of intraocular pressure; theragnostics; use of nanoparticles to treat choroidal new vessels, prevent scarring after glaucoma surgery, and treat retinal degenerative disease with gene therapy; prosthetics; and regenerative nanomedicine). Nanotechnology will revolutionize our approach to current therapeutic challenges (e.g., drug delivery, postoperative scarring) and will enable us to address currently unsolvable problems (e.g., sight-restoring therapy for patients with retinal degenerative disease). Obstacles to the incorporation of nanotechnology remain, such as safe manufacturing techniques and unintended biological consequences of nanomaterial use. These obstacles are not insurmountable, and revolutionary treatments for ophthalmic diseases are expected to result from this burgeoning field.