**Core Concept**
Childhood blindness can result from various ocular and systemic conditions. While some causes are preventable, others are congenital or acquired due to infections, nutritional deficiencies, or other factors.

**Why the Correct Answer is Right**
Congenital dacryocystitis is typically a self-limiting condition that resolves spontaneously or with minor intervention. It is characterized by inflammation of the lacrimal sac, often due to an obstruction in the nasolacrimal duct. Although it can cause discomfort and tearing, it rarely leads to permanent vision loss or blindness. In contrast, other options listed are more likely to result in significant visual impairment.

**Why Each Wrong Option is Incorrect**
**Option A:** Malnutrition can lead to childhood blindness through conditions such as vitamin A deficiency, which causes night blindness and can progress to complete blindness if left untreated. Malnutrition can also contribute to other conditions like xerophthalmia.

**Option B:** Glaucoma is a group of eye conditions that can lead to increased intraocular pressure, causing damage to the optic nerve and potentially resulting in blindness. Congenital glaucoma, in particular, is a significant cause of childhood blindness.

**Option C:** Ophthalmia neonatorum is an infection of the eye that can occur in newborns, often due to Neisseria gonorrhoeae or Chlamydia trachomatis. If left untreated, it can cause severe damage to the cornea and lead to blindness.

**Clinical Pearl / High-Yield Fact**
Remember that vitamin A deficiency is a leading cause of preventable childhood blindness worldwide. Ensuring adequate vitamin A intake through diet or supplements can significantly reduce the risk of night blindness and other ocular complications.

**Correct Answer:**
✓ Correct Answer: D. Congenital dacryocystitis.