**Core Concept**
Primary glaucoma refers to a group of eye disorders characterized by increased intraocular pressure (IOP) without any identifiable secondary cause. It is often associated with the aging process and can lead to optic nerve damage and vision loss if left untreated.

**Why the Correct Answer is Right**
Among the options, **c) Pigmentary glaucoma** is a classic example of primary glaucoma. It is caused by the dispersion of pigment from the iris, which can lead to the clogging of the trabecular meshwork and increased IOP. This condition is often seen in young to middle-aged individuals with a history of uveitis or trauma. The pathophysiology involves the interaction between pigment and the trabecular meshwork, leading to reduced aqueous outflow and increased IOP.

**Why Each Wrong Option is Incorrect**
* **Option A:** Juvenile glaucoma is a secondary form of glaucoma that typically presents in children and young adults. It is often associated with congenital or developmental anomalies, such as developmental glaucoma or anterior segment dysgenesis.
* **Option B:** Steroid-induced glaucoma is a secondary form of glaucoma caused by the long-term use of corticosteroids, which can lead to increased IOP and optic nerve damage. It is a type of secondary glaucoma.
* **Option D:** Congenital glaucoma is a secondary form of glaucoma that presents in infants and young children. It is often associated with developmental anomalies, such as a shallow anterior chamber or a poorly developed trabecular meshwork.

**Clinical Pearl / High-Yield Fact**
Pigmentary glaucoma is often associated with a history of uveitis or trauma, and patients may present with symptoms such as eye pain, redness, and blurred vision. A key clinical finding is the presence of pigment dispersion on the corneal endothelium or in the anterior chamber.

**Correct Answer:** C. Pigmentary glaucoma