Fifty years ago, it was common to classify countries into 3 categories: the affluent advanced countries, followed by the developing countries, and then the very poor undeveloped societies. This general classification was essentially based on financial and cultural status. Unfortunately, the countries included in the original list have mostly remained under these classifications as if they were still true, thereby confusing the present status and realities of the different countries and regions throughout the world.
Benjamin F. Boyd. Present Status of Ophthalmology in Latin America. Arch Ophthalmol. 2005;123(10):1433–1434. doi:10.1001/archopht.123.10.1433