Challenges and opportunities for drug delivery to the posterior of the eye

•The development of efficacious ocular drug delivery systems to treat diseases of the back of the eye faces many challenges due to the unique anatomy and physiology of the eye.•Nanotechnology in ophthalmic formulations may improve the therapeutic efficacy of some drug therapies.•The development of minimally or noninvasive drug delivery systems shows positive preclinical outcomes in animal models.•For the successful clinical translation of any ocular drug delivery technology, the use of appropriate animal models is key.