In a child with an absent red reflex, which imaging modality is often preferred to evaluate for retinoblastoma while minimizing radiation exposure?

• A. CT scan
• B. Ultrasound
• C. MRI
• D. X-ray

Answer: (C)

When a child has an absent red reflex and retinoblastoma is a concern, the goal is to assess the tumor thoroughly while avoiding radiation. MRI provides superb soft-tissue detail of the globe, orbit, optic nerve, and brain, allowing you to determine tumor size, whether the tumor has invaded the optic nerve or choroid, and whether there is intracranial or extraocular extension. This comprehensive view is essential for accurate staging and treatment planning, and it avoids ionizing radiation entirely.

Ultrasound is a useful, radiation-free tool to confirm the presence of an intraocular mass and estimate its size, but it doesn’t reliably evaluate intracranial extension or optic nerve involvement. CT and X-ray can reveal calcifications characteristic of retinoblastoma, but they expose the child to ionizing radiation, making them less preferred when MRI can provide the needed information without radiation.