The primary objective of this study is to evaluate the efficacy and safety of the topical ophthalmic administration of OCS- 01 as compared to Vehicle in participants with Diabetic Macular Edema (DME).

A Phase 2/3 Pivotal Double-masked, Randomized, Vehicle-controlled, 2 stage, Multicenter Study of the Efficacy and Safety of OCS-01 Eye Drops in Participants with Diabetic Macular Edema

Stage 1: To select a dose and dosing regimen for OCS-01 in participants with DME and evaluate the efficacy and safety of OCS-01 as compared to Vehicle in participants with DME.

Stage 2: To evaluate the efficacy and safety of OCS-01 as compared to Vehicle at Week 52 in participants with DME.

Inclusion Criteria (selection) - Stage 1:

1. Have a signed informed consent form before any study-specific procedures are performed.
2. Have DME with presence of intraretinal and/or subretinal fluid in the study eye, with central subfield thickness (CST) of ≥310 µm by SD-OCT at screening (Visit 1) (as assessed by an independent reading center).
3. Have a documented diagnosis of type 1 or type 2 diabetes mellitus at Visit 1 (Screening).

Inclusion Criteria (selection) - Stage 2:

1. Have a signed informed consent form before any study-specific procedures are performed.
2. Have DME with presence of intraretinal and/or subretinal fluid in the study eye, with central subfield thickness (CST) of ≥310 µm by SD-OCT at screening (Visit 1) (as assessed by an independent reading center).
3. Have a documented diagnosis of type 1 or type 2 diabetes mellitus prior to Visit 1 (Screening).

Exclusion criteria (selection) - Stage 1 and Stage 2:

1. Have macular edema considered to be because of a cause other than DME.
2. Have a decrease in BCVA because of causes other than DME.
3. Have a known history of significant macular ischemia which would prevent gain in visual acuity in the study eye.