The purpose of this study is to determine if intravitreal infliximab is a safe and effective treatment for macular edema secondary to diabetes.

Participants with diabetic macular edema will be treated with one injection of intravitreal infliximab (2.0mg/0.05ml) and followed for three months. Outcomes that be assessed include best-corrected visual acuity, macular thickness as measured by optical coherence tomography, and electroretinogram responses.

Inclusion Criteria:

1. Participant must be 18 years of age or older.

2. Participant has DME that is not amenable to treatment with laser photocoagulation or has been refractory to laser photocoagulation.

3. Participant must have a negative PPD skin test.

4. Participant must understand and sign the protocol's informed consent document.

5. Participants must have DME as defined by all of the following criteria:

   1. Presence of diabetes (type I or type II)
   2. Macular edema defined as a central macular thickness of ≥ 250μm on OCT.

6. Participant must have visual acuity between 20/40 and hand motions in the study eye.

7. Participant must have a steady fixation in the study eye and media clear enough for good quality imaging.

8. Female participants of childbearing potential must not be pregnant or breast-feeding, must have a negative pregnancy test at screening and must practice an adequate method of birth control. Males able to father a child must agree to practice birth control. Acceptable methods of birth control include hormonal contraception (birth control pills, injected hormones or vaginal ring), intrauterine device, barrier methods with spermicide (diaphragm with spermicide, condom and spermicide) or surgical sterilization (hysterectomy, tubal ligation or vasectomy in a partner). If a participant is of childbearing potential, she must be willing to undergo monthly urine pregnancy tests. Both males and females must agree to use adequate birth control for three months after the intravitreal infliximab injection.

If both eyes of a participant qualify for inclusion, then the eye with worse visual acuity will be chosen.

Exclusion Criteria:

1. Participant is in another investigational study and actively receiving study therapy.
2. Participant has proliferative diabetic retinopathy.
3. Participant is unable to comply with study procedures or follow-up visits.
4. Participant has multiple sclerosis or symptoms suggestive of multiple sclerosis.
5. Participant has evidence of ocular disease other than DME in either eye that may confound the outcome of the study (e.g., uveitis, age-related macular degeneration, vitreomacular traction, moderate/severe myopia, etc.).
6. Participant is expected to need ocular surgery or panretinal photocoagulation in the study eye during the course of the study.
7. Participant has undergone ocular surgery or an intravitreal/periocular steroid injection in the study eye within the past 3 months.
8. Participant has had a YAG laser capsulotomy or intravitreal anti-VEGF treatment in the study eye within the past 6 weeks.
9. Participant has had a pars plana vitrectomy in the study eye.
10. Participant is on ocular or systemic medications known to be toxic to the lens, retina, or optic nerve.
11. Participant with a history of ocular herpes simplex virus infection in the study eye.
12. A condition that, in the opinion of the investigator, would preclude participation in the study (e.g., unstable medical status including blood pressure and glycemic control).