**Core Concept**
Rubeosis iridis, also known as neovascularization of the iris, is a condition characterized by the formation of new, fragile blood vessels on the surface of the iris. This is often a result of ischemic or hypoxic conditions in the retina, leading to the release of angiogenic factors that stimulate the growth of new vessels.

**Why the Correct Answer is Right**
Rubeosis iridis typically occurs in response to conditions that lead to retinal ischemia or hypoxia, such as diabetic retinopathy, central retinal vein occlusion, or retinal detachment. The growth of new vessels on the iris can lead to complications such as neovascular glaucoma, where the new vessels obstruct the trabecular meshwork and increase intraocular pressure. In the absence of such conditions, rubeosis iridis is not typically seen.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because rubeosis iridis can be seen in conditions other than those listed, such as retinal artery occlusion or retinal tumors.
**Option B:** This option is incorrect because rubeosis iridis is not exclusive to the conditions listed, and its absence does not rule out other potential causes.
**Option C:** This option is incorrect because rubeosis iridis can occur in the presence of other ocular conditions, such as uveitis or glaucoma.

**Clinical Pearl / High-Yield Fact**
Rubeosis iridis is a sign of underlying retinal ischemia or hypoxia, and its presence should prompt further investigation into the underlying cause.

**Correct Answer:** C.