The eye, which is under constant exposure to environmental pathogens, has evolved various anatomic and immunological barriers critical to the protection of tissues lacking regenerative capacity, and the maintenance of a clear optic pathway essential to vision. By bypassing the ocular barriers, intravitreal (IVT) injection has become the mainstay for the delivery of drugs to treat conditions that affect the back of the eye. Both small molecules and biotherapeutics have been successfully administered intravitreally, and several drugs have been approved for the treatment of (wet) age-related macular degeneration and diabetic macular edema. However, IVT injection is an invasive procedure, which requires sufficient technical expertise from the healthcare professional administering the drug.Potential side effects include bleeding, retinal tear, cataracts, infection, uveitis, loss of vision, and increased ocular pressure. Pharmaceutical companies often F I G U R E 1 Structures and compartments of the eye. 19 Hematoxylin-eosin-stained section of a whole dog eye. The anterior segment is divided into the anterior and posterior chambers, which are anatomically delineated by the AH; cornea, sclera, and conjunctiva; ICA; the ciliary processes, and iris body. Behind the lens, the posterior segment includes the VB; retina and ora serrata; the choroid and sclera; and the optic nerve.