This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
A one year old child having leucocoria was detected to be having a unilateral, large retinoblastoma filling half the globe. Which of the following is the therapy of choice? 
Select and explain. 
A. Enucleation, B. Chemotherapy followed by local dyes, C. Scleral radiotherapy followed by chemotherapy, D. Direct Laser ablation using photo dynamic cryotherapy
A: Enucleation
Answer: A: Enucleation 
Explanation: Since the child is having a very large retinoblastoma filling more than half the globe the treatment of choice is enucleation. Eyeball is enucleated along with maximum length of the optic nerve without perforating the eyeball. Enucleation is indicated in the treatment of retinoblastoma when the tumor involves more than half the retina, optic nerve is involved and when glaucoma is present and anterior chamber is involved. Ref: Comprehensive Ophthalmology By AK Khurana, 4th Edition, Page 283.