**Core Concept**
The intercanthal distance is a crucial measurement in ophthalmology and plastic surgery, referring to the distance between the medial canthi (the medial angles of the eyes). Telecanthus is a condition characterized by an increased intercanthal distance, which can be caused by various factors such as congenital anomalies, trauma, or surgical interventions.

**Why the Correct Answer is Right**
The correct answer is based on the definition of telecanthus. Telecanthus is typically defined as an intercanthal distance greater than 32-35 mm in adults or 25-30 mm in children. This increased distance can lead to a wider appearance of the eyes, which is a key diagnostic feature of telecanthus. The measurement of intercanthal distance is essential in assessing the severity of telecanthus and planning appropriate treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a clear threshold for telecanthus. While an increased intercanthal distance is a key feature, a specific value is necessary to diagnose telecanthus.
**Option B:** This option is incorrect because it suggests that telecanthus is characterized by a decreased intercanthal distance, which is the opposite of the actual definition.
**Option C:** This option is incorrect because it suggests a specific value for the intercanthal distance in children, but does not provide a clear threshold for telecanthus.

**Clinical Pearl / High-Yield Fact**
A key aspect to remember when assessing telecanthus is that it can be caused by a variety of factors, including congenital anomalies, trauma, or surgical interventions. A thorough medical history and physical examination are essential in diagnosing telecanthus and planning appropriate treatment.

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