Patients undergoing surgery for complications related to diabetes will be recruited.

Proliferative Diabetic Retinopathy patients undergoing pars plana vitrectomy will be randomized whether or not to receive intravitreal bevacizumab at the conclusion of the operation.

Inclusion Criteria:

1. Subject age is > 18
2. Subject consents to study participation and is capable of 6 months of follow-up.
3. The subject has type I or II Diabetes Mellitus with active PDR in the study eye.
4. Best-corrected spectacle visual acuity (BCSVA) on the Snellen eye chart ranges from 20/40 to Hand Motions in the study eye.
5. The subject is determined to need a PPV because of reduced BCSVA principally from a non-clearing vitreous hemorrhage, TRD, fibrous proliferation, or a combination of the three. When non-clearing vitreous hemorrhage is the principal reason for PPV, the hemorrhage must have been present by subjective history for at least 3 months. When TRD is the principal reason for PPV, the TRD must be threatening (within one disc diameter) or involving the fovea. When fibrovascular proliferation is the principal reason for PPV, it must be extensive (>3 clock hours) and threatening (within one disc diameter) or involving the fovea.
6. Only one eye per patient is eligible for the study.

Exclusion Criteria:

1. Subject is known to have a significant retinal/optic nerve disease otherwise unrelated to Diabetes Mellitus, which in the opinion of the examiner is responsible for two or more lines of reduced BCSVA (macular degeneration, optic neuritis, glaucoma, amblyopia, etc.) in the study eye.

2. Subject has a significant corneal opacity, which in the opinion of the examiner, is responsible for two or more lines of reduced BCSVA (corneal scar, ectasia, etc.) in the study eye.

3. Subject has had a previous vitrectomy (anterior or PPV) in the study eye.

4. Subject has uncontrolled neovascular glaucoma (intraocular pressure > 30 mmHg despite medical/surgical treatment) in the study eye.

5. Subject has uncontrolled hypertension (systolic > 200 mmHg or diastolic > 120 mmHg) despite adherence to a multiple anti-hypertensive medication regimen.

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Not sure at this point.

Patients and the specialist recording outcomes will be masked.