**Core Concept**
Elschnig pearls are a characteristic ophthalmological feature associated with congenital cataracts, particularly in the context of developmental anomalies. They refer to small, rounded opacities or "pearls" within the lens of the eye, often seen in cataracts that are present at birth or develop early in life.

**Why the Correct Answer is Right**
Elschnig pearls are formed due to the abnormal accumulation of lens fibers, which can occur as a result of a disruption in the normal process of lens development. This disruption can lead to the formation of small, rounded opacities within the lens, which are visible upon examination. The specific mechanism behind the formation of Elschnig pearls is not fully understood, but it is thought to be related to the abnormal organization of lens fibers during embryonic development.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Elschnig pearls are not typically associated with age-related cataracts, which are a common cause of cataract formation in adults.
**Option B:** This option is incorrect because Elschnig pearls are not a feature of posterior capsular opacification, which is a common cause of cataract formation after cataract surgery.
**Option C:** This option is incorrect because Elschnig pearls are not a feature of secondary cataracts, which are caused by a variety of factors including trauma, inflammation, and medication side effects.

**Clinical Pearl / High-Yield Fact**
Elschnig pearls are an important clinical finding that can be associated with congenital cataracts and other developmental anomalies of the eye. Recognizing the presence of Elschnig pearls can help guide further evaluation and management of patients with cataracts.

**Correct Answer: D.**