**Core Concept**
The patient's presentation of loss of central vision, normal ERG (Electroretinogram), and abnormal EOG (Electrooculogram) suggests a disorder affecting the retinal pigment epithelium (RPE) or the choroid. The RPE plays a crucial role in maintaining photoreceptor function, and its dysfunction can lead to visual impairment.

**Why the Correct Answer is Right**
The abnormal EOG result indicates a problem with the RPE function, which is responsible for generating the electrical potential difference between the front and back of the eye. This is due to the RPE's ability to accumulate and regenerate rhodopsin, a critical photopigment in the retina. The normal ERG result suggests that the photoreceptors themselves are functioning properly. Therefore, the likely diagnosis is a disorder affecting the RPE or the choroid.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a normal ERG result would be expected in conditions where the photoreceptors are functioning properly, such as in cone monochromacy or achromatopsia.

**Option B:** This option is incorrect because a normal EOG result would be expected in conditions where the RPE function is preserved, such as in age-related macular degeneration.

**Option C:** This option is incorrect because a normal ERG result would be expected in conditions where the photoreceptors are functioning properly, such as in cone monochromacy or achromatopsia.

**Clinical Pearl / High-Yield Fact**
The EOG is a useful diagnostic tool for detecting disorders affecting the RPE, such as Stargardt disease or choroideremia. A low EOG result can indicate RPE dysfunction, which may precede visual impairment.

**Correct Answer:** C. Choroideremia.