**Core Concept**
Distant direct ophthalmoscopy is a technique used to examine the posterior segment of the eye, including the retina and macula. It involves using a direct ophthalmoscope at a specific distance from the patient's eye to obtain a clear view of the ocular fundus.

**Why the Correct Answer is Right**
The correct distance for distant direct ophthalmoscopy is approximately 25-30 cm. This distance allows the examiner to see the entire ocular fundus, including the posterior pole, while minimizing the effect of the near point of the eye. The near point of the eye is the closest distance at which an object can be held and still be seen clearly by a person with normal vision. At a distance of 25-30 cm, the examiner can see the characteristic features of the ocular fundus, such as the optic disc, macula, and retinal vessels.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a distance of 10 cm is too close to the eye, causing the examiner to see only a small portion of the ocular fundus.
**Option B:** This option is incorrect because a distance of 50 cm is too far from the eye, making it difficult to see the posterior segment of the eye clearly.
**Option C:** This option is incorrect because a distance of 15 cm is closer to the eye than the optimal distance, resulting in a restricted view of the ocular fundus.

**Clinical Pearl / High-Yield Fact**
To perform distant direct ophthalmoscopy, the examiner should adjust the focus of the ophthalmoscope to obtain a clear view of the ocular fundus. The light from the ophthalmoscope should be adjusted to minimize glare and ensure that the examiner sees the characteristic features of the ocular fundus.

**Correct Answer:** C. 25-30 cm.