**Core Concept**
The incidence of myopia refers to the number of new cases of myopia that occur within a specified time period (in this case, 2011) in a defined population. It is a measure of the risk of developing myopia over a specific period.

**Why the Correct Answer is Right**
To calculate the incidence of myopia, we need to identify the number of new cases that occurred in 2011 and divide it by the population at risk. The population at risk is the total population minus those who already have the disease on January 1, 2011. In this scenario, the population at risk is 5000 - 500 = 4500. The number of new myopia cases in 2011 is given as 90.

Incidence = Number of new cases / Population at risk
= 90 / 4500
= 0.02 or 2%

**Why Each Wrong Option is Incorrect**

**Option A:** This option is not provided, so we'll skip it.

**Option B:** This option is not provided, so we'll skip it.

**Option C:** This option is not provided, so we'll skip it.

**Option D:** This option is not provided, so we'll skip it.

**Clinical Pearl / High-Yield Fact**
Remember the formula for incidence: Number of new cases / Population at risk. This can be applied to any disease or condition in epidemiology.

**Correct Answer: D. 2%**