**Core Concept**
The patient's symptoms suggest a condition affecting the cornea or lens, causing light to be refracted abnormally and perceived as colored haloes, particularly in low light conditions. This condition is associated with a normal intraocular pressure (IOP), which rules out glaucoma as a cause.

**Why the Correct Answer is Right**
The patient's symptoms are characteristic of _keratoconus_, a progressive thinning of the cornea that leads to irregular astigmatism and myopia. This condition causes light to be refracted abnormally, resulting in symptoms such as seeing colored haloes around lights, particularly in the evening. Keratoconus is often associated with a normal IOP, which distinguishes it from glaucoma.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option might be incorrect because keratoconus is not typically associated with a sudden onset of symptoms. However, the question does not provide specific information regarding the duration of symptoms, making this option less likely to be eliminated based solely on the information provided.
* **Option B:** This option might be incorrect because the patient's symptoms do not suggest a condition affecting the vitreous or retina, such as retinal detachment or vitreous hemorrhage, which would typically present with symptoms such as floaters, flashes of light, or decreased vision.
* **Option C:** This option might be incorrect because the patient's symptoms do not suggest a condition affecting the lens, such as cataract, which would typically present with symptoms such as decreased vision, glare, or double vision.

**Clinical Pearl / High-Yield Fact**
Keratoconus often presents with a normal IOP, which distinguishes it from glaucoma. A key clinical feature of keratoconus is the presence of colored haloes around lights, particularly in low light conditions.

**Correct Answer:** C. Keratoconus.