**Core Concept**
In ophthalmology, circumcorneal congestion is a sign of increased intraocular pressure (IOP) due to damage to the globe, leading to inflammation and subsequent iris sphincter spasm. This is a classic presentation of angle-closure glaucoma, which can be a life-threatening emergency.

**Why the Correct Answer is Right**
The correct answer is the test used to diagnose and manage angle-closure glaucoma. In this scenario, the patient's symptoms of circumcorneal congestion, pain, and decreased vision warrant immediate assessment of IOP and the anterior chamber. A **Tonometry** test, specifically **Tonometer**, is used to measure IOP, which is crucial in diagnosing and managing glaucoma. This is done by gently pressing a probe against the cornea to measure the resistance to indentation, which correlates with IOP.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is not a relevant or useful test in this clinical scenario.
* **Option B:** This is not a suitable test for measuring IOP.
* **Option C:** This is not a relevant test in the diagnosis and management of angle-closure glaucoma.

**Clinical Pearl / High-Yield Fact**
When assessing a patient with blunt trauma to the eye, always prioritize the possibility of angle-closure glaucoma, as this is a medical emergency that requires prompt diagnosis and treatment to prevent vision loss. Always perform a thorough eye examination, including tonometry, to evaluate IOP and anterior chamber depth.

**Correct Answer: C. Tonometer**