**Core Concept**
Economic blindness refers to a level of visual impairment that significantly affects an individual's ability to engage in gainful employment, thereby impacting their economic independence. This concept is often used in the context of disability assessments and social welfare programs.

**Why the Correct Answer is Right**
The correct answer is related to the impact of visual impairment on an individual's earning capacity. Economic blindness is not solely defined by the cost of treatment but rather by the extent to which it hinders an individual's ability to work and contribute to society. This concept takes into account the individual's functional limitations and how they affect their daily life, including their ability to earn a living.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because economic blindness is not solely limited to preventing an individual from earning their wages. It encompasses a broader range of activities that are essential for economic independence, such as self-care, social interactions, and other daily tasks.

**Option B:** This option is incorrect because economic blindness is not necessarily defined by the cost of treatment. While the cost of treatment may be a factor in determining the economic burden of blindness, it is not the primary criterion for defining economic blindness.

**Option C:** This option is incorrect because it is too narrow in scope. Economic blindness is not solely related to visual impairment but also encompasses other factors that affect an individual's ability to engage in gainful employment.

**Option D:** This option is incorrect because it is not a recognized definition of economic blindness. The correct definition focuses on the impact of visual impairment on an individual's ability to earn a living, rather than other factors.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that economic blindness is a functional concept that takes into account the individual's ability to engage in daily activities, including work, rather than just the severity of their visual impairment.

**Correct Answer:** 1. level of blindness that prevents an individual from earning his wages.