**Core Concept**
Retinoblastoma is a malignant tumor of the retina that primarily affects children. The treatment of retinoblastoma involves a combination of local and systemic therapies to prevent tumor spread and preserve vision.

**Why the Correct Answer is Right**
The treatment of retinoblastoma is multimodal and depends on the stage and size of the tumor. **Enucleation**, or surgical removal of the eye, is often the primary treatment for large tumors or those that have spread to the optic nerve. This is because retinoblastoma is highly malignant and can spread to other parts of the body if left untreated. **External beam radiation therapy** and **chemotherapy** are also used to treat retinoblastoma, particularly for smaller tumors or those that are resistant to surgery.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while **cryotherapy** is a treatment for retinoblastoma, it is typically used for small, localized tumors and is not the primary treatment for larger or more advanced tumors.
**Option B:** This option is incorrect because **laser therapy** is not a standard treatment for retinoblastoma and is not effective for larger or more advanced tumors.
**Option C:** This option is incorrect because **photocoagulation** is a treatment for diabetic retinopathy, not retinoblastoma.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that retinoblastoma is a highly malignant tumor that requires prompt treatment to prevent spread to other parts of the body. Early detection and treatment are critical for preserving vision and preventing metastasis.

**Correct Answer: A. Enucleation**