An intravitreal injection is an injection of a drug directly into the cavity of the eye, namely, into the vitreous body, which occupies a large part of the eye. An intravitreal injection provides highly effective, targeted delivery of the drug to the posterior chamber of the eye, thereby creating an optimal concentration of the drug over a long period (2-9 weeks). The structural features of the eye do not allow drugs injected intravenously or intramuscularly to be delivered to the retina. Therefore, the only way to achieve this is intravitreal injection. To discover more info about the procedure, look here https://myvisioncare.org/blog/intravitreal-injections-for-the-treatment-of-diabetic-macular-edema