## **Core Concept**
Retinoblastoma is a malignant tumor of the retina, primarily affecting young children. Leucocoria, or white pupillary reflex, is a common presenting sign. The management of retinoblastoma depends on the stage and extent of the disease.

## **Why the Correct Answer is Right**
For a unilateral, large retinoblastoma filling half the globe in a one-year-old child, the current therapy would likely involve **enucleation** of the affected eye. This is because the tumor is large and likely to be advanced, making it difficult to preserve vision. Enucleation is often recommended for advanced unilateral retinoblastoma to prevent tumor spread and ensure the child's survival.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Chemotherapy alone might not be sufficient for a large tumor filling half the globe, as it may not adequately address the tumor's size and potential for spread.
- **Option B:** Radiation therapy could be considered for smaller tumors or to avoid enucleation, but for a tumor of this size, it might not be the most effective standalone treatment due to potential side effects and the risk of incomplete tumor regression.
- **Option C:** This option seems to suggest a combination or a different approach but is not specified; however, given the context, enucleation is often the most direct and effective treatment for large tumors.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the management of retinoblastoma is highly individualized based on the tumor's size, location, and stage, as well as the child's age and overall health. For advanced unilateral retinoblastoma, enucleation is often necessary to prevent metastasis and ensure survival.

## **Correct Answer:** D. Enucleation.