**Core Concept:** Neovascular glaucoma is a rare complication of uncontrolled diabetes mellitus, characterized by the formation of new blood vessels on the iris, leading to increased aqueous humor production, raised intraocular pressure, and potential vision loss.

**Why the Correct Answer is Right:** Neovascular glaucoma occurs due to the abnormal proliferation of blood vessels (neovascularization) in the iris. These new blood vessels can obstruct the drainage angle of the eye, impairing the outflow of aqueous humor and increasing intraocular pressure (IOP). In the context of the question, options related to unrelated pathology would be wrong.

**Why Each Wrong Option is Incorrect:**

A. **Vascular endothelial growth factor (VEGF)** is a protein that stimulates angiogenesis (new blood vessel formation), which is relevant to pathologies involving abnormal angiogenesis, but not specific to neovascular glaucoma.

B. **Primary open-angle glaucoma** is a common form of glaucoma, characterized by elevated IOP due to structural abnormalities in the drainage angle. This option is incorrect because it refers to a different type of glaucoma.

C. **Tractional glaucoma** is a form of glaucoma caused by tractional forces on the trabecular meshwork, leading to elevated IOP. This option is incorrect because it refers to a different type of glaucoma.

D. **Glaucoma due to lens-induced uveitis** is a type of glaucoma caused by inflammation of the iris and uvea due to a lens-related condition. This option is incorrect because it refers to a different type of glaucoma.

**Clinical Pearl:** While neovascular glaucoma is a complication of uncontrolled diabetes, it is essential to understand the underlying mechanisms and types of glaucoma to diagnose and manage patients correctly. This understanding helps in distinguishing between different forms of glaucoma and choosing the appropriate treatment strategy.