**Core Concept**
The national blindness control program aims to reduce the prevalence of blindness in India, with a focus on cataract surgery as a key intervention. Follow-up of cataract operations is crucial to ensure the success of the surgery and to identify any potential complications.

**Why the Correct Answer is Right**
The correct answer is **A. Ophthalmic assistants**. Ophthalmic assistants play a vital role in the follow-up of cataract operations, as they are responsible for checking the vision of patients, monitoring for any signs of complications, and providing basic eye care services. This is in line with the principles of the national blindness control program, which emphasizes the importance of community-based eye care services.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect because **General Duty Medical Officers (GDMOs)** are not typically responsible for follow-up of cataract operations in community settings. While GDMOs may provide medical care, they are not specifically trained in ophthalmology or community-based eye care.

**Option C:** This option is incorrect because **Medical Officers** may provide medical care, but they are not specifically trained in ophthalmology or community-based eye care. They may not be familiar with the specific needs of patients undergoing cataract surgery.

**Option D:** This option is incorrect because **Refractionists** are trained to perform refraction and prescribe glasses, but they are not responsible for follow-up of cataract operations. Their role is limited to refractive error management.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that follow-up of cataract operations is a critical component of the national blindness control program, and ophthalmic assistants play a vital role in this process. This highlights the importance of community-based eye care services in reducing the burden of blindness in India.

**Correct Answer:** A. Ophthalmic assistants