**Core Concept:** Vitamin A deficiency is a common nutritional disorder in developing countries, causing various ocular, skeletal, and immune system abnormalities. Vitamin A is essential for maintaining corneal epithelial integrity, visual acuity, and cellular differentiation. Keratomalacia, a severe form of vitamin A deficiency, can lead to corneal ulceration and vision loss.

**Why the Correct Answer is Right:** In this scenario, a 18-month-old baby weighing 10 kg is suffering from keratomalacia due to vitamin A deficiency. The recommended dose for treating severe vitamin A deficiency is approximately 50,000 IU (International Units) of vitamin A. The dose is adjusted based on the patient's body weight.

**Why Each Wrong Option is Incorrect:**

A. 25,000 IU: This dose is insufficient for a 18-month-old baby weighing 10 kg, as it does not cover the required amount necessary for severe vitamin A deficiency treatment.

B. 75,000 IU: While this dose is higher than the correct answer, it is still excessive for a child of this age and weight, potentially causing side effects like hepatotoxicity and myopathy.

C. 100,000 IU: This dose is too high and could lead to serious side effects like hepatotoxicity and myopathy. It is not suitable for a 18-month-old baby weighing 10 kg.

D. 30,000 IU: This dose is inadequate for treating severe vitamin A deficiency in a 18-month-old baby weighing 10 kg.

**Clinical Pearl:**

In treating vitamin A deficiency in children, it is essential to consider the patient's age, weight, and disease severity when determining the appropriate dose. Overestimating or underestimating the dose can lead to inadequate treatment or severe side effects.

**Correct Answer:** D. 75,000 IU

In a child of this age and weight, administering 75,000 IU of vitamin A is a suitable treatment dose for severe vitamin A deficiency and keratomalacia. This dose is appropriate for a 18-month-old child weighing 10 kg, ensuring adequate treatment while minimizing potential side effects.