**Core Concept**
The question tests knowledge of protozoa that can cause ocular infections, specifically focusing on the causative agents of eye diseases. **Protozoal infections** can affect various parts of the body, including the eyes, leading to serious complications.

**Why the Correct Answer is Right**
The correct answer is related to **Acanthamoeba**, which can cause **Acanthamoeba keratitis**, a serious infection of the cornea. This infection is often associated with contact lens use and can lead to severe visual impairment if not treated promptly.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although it may be a protozoan, it is not specifically known for causing eye infections.
**Option B:** Incorrect as it is not typically associated with ocular diseases.
**Option C:** Incorrect because it is not the primary protozoan causing eye infections.
**Option D:** Incorrect as it is not the correct answer, which is related to Acanthamoeba.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Acanthamoeba keratitis** is a significant risk for contact lens wearers, especially if they do not follow proper hygiene practices.

**Correct Answer:** D. Acanthamoeba.