**Core Concept**
Subconjunctival cysts are a type of ocular manifestation that can arise due to various infectious and parasitic agents. These cysts are formed when the body's immune response attempts to wall off and contain the pathogen, leading to the accumulation of fluid and the formation of a cystic structure.

**Why the Correct Answer is Right**
Cysticercosis is a parasitic infection caused by the larval stage of the pork tapeworm (Taenia solium). When the larva penetrates the conjunctiva, it can induce a localized immune response, leading to the formation of a subconjunctival cyst. This cyst is typically filled with a clear, gelatinous material and may cause symptoms such as pain, redness, and vision disturbances. The correct diagnosis of cysticercosis is essential to prevent further complications, such as the development of uveitis or glaucoma.

**Why Each Wrong Option is Incorrect**
**Option A:** Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, but it primarily affects the retina and choroid, leading to retinochoroiditis, rather than causing subconjunctival cysts.

**Option C:** Leishmaniasis is a parasitic infection caused by Leishmania species, which typically affects the skin, mucous membranes, and internal organs, but it is not commonly associated with subconjunctival cysts.

**Option D:** Chagas disease is a parasitic infection caused by Trypanosoma cruzi, which primarily affects the heart, gastrointestinal tract, and nervous system, but it is not typically associated with subconjunctival cysts.

**Clinical Pearl / High-Yield Fact**
Cysticercosis can be diagnosed using imaging studies such as ultrasound or CT scans, which can reveal the characteristic appearance of a subconjunctival cyst. It is essential to consider cysticercosis in the differential diagnosis of subconjunctival cysts, especially in patients with a history of pork consumption or travel to endemic areas.

**✓ Correct Answer: B. Cysticercosis**