An apparatus includes a body, a needle, a catheter, and an actuator assembly. The needle extends distally from the body. The needle has an inner wall defining a needle lumen. The needle lumen is in fluid communication with a fluid port of the body. The catheter is slidably disposed in the needle lumen. The catheter has a catheter lumen. The first actuator assembly is configured to translate the catheter within and relative to the needle. The apparatus may also include an actuator assembly that is configured to rotate the needle relative to the body. The apparatus may be used to first deliver a leading bleb of fluid to the subretinal space in a patient's eye via the needle. The apparatus may then be used to deliver a therapeutic agent to the subretinal space in the patient's eye via the catheter.